text: Thus, the charge q of a source reduces its energy as measured at the boundary by q2/2k. This exactly matches the shift in the conformal blocks in equation (3.43). It also implies that the matching to the spectrum in a black hole background generalizes immediately. Because the Chern-Simons ﬁeld and the metric are not coupled in the bulk, black hole solutions are just BTZ with a shifted mass parameter, M → M − q2/2k, and a background proﬁle for the Chern-Simons ﬁeld [53]. For a light neutral CFT operator in the background of a heavy charged state, this shift is the only change as compared to a heavy neutral state. If the light operator is charged, the background Chern-Simons ﬁeld produces the additional dependence (3.44), which completely factorizes. The spectrum of twists (or quasi-normal modes) at large spin can then be read oﬀ from the bootstrap equation exactly as in [25]. The only two changes are that the “binding” energy depends on h −q2/2k rather than h , and there is an additional i i i contribution q q /k: B S (cid:114) q q h − q2 q2 τ = 2h + B S + 2i 24 B B − 1(n + h − S ). (4.11) n B S k 2kc 2k 4.3 Matching of correlators It would be interesting to see how the large c Virasoro blocks arise as contributions to heavy-light 4-pt correlators obtained from Feynman diagram computations in AdS . We 3 previously analyzed the case of the identity block [25], but matching with more general correlators is signiﬁcantly more challenging. Here we will conﬁne our analysis to the case of 3-pt correlators. This will be suﬃcient to show that the somewhat mysterious rescaling of δ → δ /α in the Virasoro conformal block is a kinematical consequence of the conformal H H transformation to the w coordinates. In a ﬂat background metric, the CFT 3-pt correlator is − (cid:104)O (∞)O (0)O (z)(cid:105) = z hL+δH. (4.12) H1 H2 L It is non-trivial to obtain this from an explicit bulk computation that includes gravita- tional backreaction, because the heavy operators have bulk-to-boundary propagators that are dressed by gravitons, and the back-reaction of the geometry on the bulk-to-boundary propagator is not suppressed. However, conformal symmetry guarantees the form of the ﬁnal result. The conformal transformation to w = zα produces a new correlator (cid:104)OH1(∞)OH2(0)OL(w)(cid:105) = w−hL+δαH . (4.13) Let us recall how this rescaling of δ from z to w coordinates can be derived from a bulk H analysis. We will write AdS in global coordinates 1 ds2 = (dt2 + dρ2 + sin2 ρ dθ2) (4.14) cos2 ρ – 20 – ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine##

text: Thus,

text: the

text: charge

text: q

text: of

text: a

text: source

text: reduces

text: its

text: energy

text: as

text: measured

text: at

text: the

text: boundary

text: by

text: This

text: exactly

text: matches

text: the

text: shift

text: in

text: the

text: conformal

text: blocks

text: in

text: equation

text: It

text: also

text: implies

text: that

text: the

text: matching

text: to

text: the

text: spectrum

text: in

text: a

text: black

text: hole

text: background

text: generalizes

text: immediately.

text: Because

text: the

text: Chern-Simons

text: ﬁeld

text: and

text: the

text: metric

text: are

text: not

text: coupled

text: in

text: the

text: bulk,

text: black

text: hole

text: solutions

text: are

text: just

text: BTZ

text: with

text: a

text: shifted

text: mass

text: parameter,

text: M

text: M

text: and

text: a

text: background

text: proﬁle

text: for

text: the

text: Chern-Simons

text: ﬁeld

text: For

text: a

text: light

text: neutral

text: CFT

text: operator

text: in

text: the

text: background

text: of

text: a

text: heavy

text: charged

text: state,

text: this

text: shift

text: is

text: the

text: only

text: change

text: as

text: compared

text: to

text: a

text: heavy

text: neutral

text: state.

text: If

text: the

text: light

text: operator

text: is

text: charged,

text: the

text: background

text: Chern-Simons

text: ﬁeld

text: produces

text: the

text: additional

text: dependence

text: which

text: completely

text: factorizes.

text: The

text: spectrum

text: of

text: twists

text: (or

text: quasi-normal

text: modes)

text: at

text: large

text: spin

text: can

text: then

text: be

text: read

text: oﬀ

text: from

text: the

text: bootstrap

text: equation

text: exactly

text: as

text: in

text: The

text: only

text: two

text: changes

text: are

text: that

text: the

text: “binding”

text: energy

text: depends

text: on

text: h

text: rather

text: than

text: h

text: and

text: there

text: is

text: an

text: additional

text: i

text: i

text: i

text: contribution

text: q

text: q

text: /k:

text: B

text: S

text: q

text: q

text: h

text: τ

text: B

text: S

text: B

text: B

text: h

text: S

text: n

text: B

text: S

text: k

text: Matching

text: of

text: correlators

text: It

text: would

text: be

text: interesting

text: to

text: see

text: how

text: the

text: large

text: c

text: Virasoro

text: blocks

text: arise

text: as

text: contributions

text: to

text: heavy-light

text: correlators

text: obtained

text: from

text: Feynman

text: diagram

text: computations

text: in

text: AdS

text: We

text: previously

text: analyzed

text: the

text: case

text: of

text: the

text: identity

text: block

text: but

text: matching

text: with

text: more

text: general

text: correlators

text: is

text: signiﬁcantly

text: more

text: challenging.

text: Here

text: we

text: will

text: conﬁne

text: our

text: analysis

text: to

text: the

text: case

text: of

text: correlators.

text: This

text: will

text: be

text: suﬃcient

text: to

text: show

text: that

text: the

text: somewhat

text: mysterious

text: rescaling

text: of

text: δ

text: δ

text: /α

text: in

text: the

text: Virasoro

text: conformal

text: block

text: is

text: a

text: kinematical

text: consequence

text: of

text: the

text: conformal

text: H

text: H

text: transformation

text: to

text: the

text: w

text: coordinates.

text: In

text: a

text: ﬂat

text: background

text: metric,

text: the

text: CFT

text: correlator

text: is

text: (∞)O

text: z

text: hL+δH.

text: L

text: It

text: is

text: non-trivial

text: to

text: obtain

text: this

text: from

text: an

text: explicit

text: bulk

text: computation

text: that

text: includes

text: gravita-

text: tional

text: backreaction,

text: because

text: the

text: heavy

text: operators

text: have

text: bulk-to-boundary

text: propagators

text: that

text: are

text: dressed

text: by

text: gravitons,

text: and

text: the

text: back-reaction

text: of

text: the

text: geometry

text: on

text: the

text: bulk-to-boundary

text: propagator

text: is

text: not

text: suppressed.

text: However,

text: conformal

text: symmetry

text: guarantees

text: the

text: form

text: of

text: the

text: ﬁnal

text: result.

text: The

text: conformal

text: transformation

text: to

text: w

text: zα

text: produces

text: a

text: new

text: correlator

text: w−hL+δαH

text: Let

text: us

text: recall

text: how

text: this

text: rescaling

text: of

text: δ

text: from

text: z

text: to

text: w

text: coordinates

text: can

text: be

text: derived

text: from

text: a

text: bulk

text: H

text: analysis.

text: We

text: will

text: write

text: AdS

text: in

text: global

text: coordinates

text: ρ

text: ρ

text: ##LTLine##

text: ##LTLine##

text: ##LTLine##

text: ##LTLine##

text: ##LTLine##

text: ##LTLine##


text: and these poles must remain in the Mellin representation of the full CFT correlator. The individual B (s, t) do not fall oﬀ exponentially as s, t → ±i∞, since the Virasoro blocks are w not analytic near w = 1. But if the sum of the B (s, t) has a good asymptotic behavior, w then the full CFT correlator will be thermal. One might also investigate factorizations as in equation (5.3) in this Mellin space language. 6 Future directions Intuition suggests that CFT operators carrying a large conserved charge may generate a classical background ﬁeld aﬀecting correlation functions in a universal way. This idea has obvious validity in the case of AdS/CFT, where heavy or charged states generate gravitational or gauge ﬁelds in AdS, but one can also look for manifestations of this eﬀect in general CFTs. We have shown that heavy operators in 2d CFTs have exactly this eﬀect, and that it can be used to compute Virasoro conformal blocks at large central charge. We also used this idea to sum up contributions from U(1) currents in the CFT. Classical gravitational and gauge ﬁelds in AdS have a universal manifestation in all CFT at large central charge. 3 2 To leading order at large central charge c, the heavy-light Virasoro blocks bear a striking imprint of thermality, and it would be interesting to explore this property in more detail. In particular, one should expect that the probability of a transition from one heavy state to − another should be weighted by a Boltzmann factor. The rescaled δH = 2πiEH1 EH2 appearing α TH in the conformal blocks of equation (3.29) seems tantalizing in this regard. In fact, in the limit of small h, δL the conformal blocks approach a universal form proportional to (1 − w)δH/α. This result might be used to argue that the rates for transitions among the heavy states take a universal thermal form. Unitary CFT correlators should not be exactly thermal. One can use the recursion relations of section to compute corrections to our c = ∞ result, but at present this is only practical if we work to low order in the coordinate w, or perhaps to ﬁrst order in 1/c. However, corrections to thermality are most likely non-perturbative in c, showing up in the Virasoro blocks at ﬁnite z or w. It would be very exciting to understand these non-perturbative corrections. CFT correlators are made from an inﬁnite sum of Virasoro blocks, so it would also be interesting to understand whether corrections to thermality arise primarily from non- perturbative corrections to the individual Virasoro blocks, or from patterns in the inﬁnite sum. An immediate question is whether one can obtain similar results using classical back- ground ﬁelds for CFTs in d > 2 dimensions. We were able to obtain very precise results for CFT by making use of the inﬁnite dimensional Virasoro algebra, so one might not expect 2 higher dimensional generalizations to be possible. However, we believe that the results of [47, 48] on the expectation value of the stress-tensor in conformally ﬂat backgrounds can be used to study heavy operators in large central charge CFTs in d = 4 and 6, perhaps after imposing some physical constraints [63] on the CFT data. It would be very interesting to generalize the analysis of [47, 48, 64], and to understand which CFT data aﬀect the result. Our analysis motivates studying CFTs in a non-trivial background metric chosen to – 26 – ##LTLine## ##LTLine##

text: and

label: paragraph

text: these

text: poles

text: must

text: remain

text: in

text: the

text: Mellin

text: representation

text: of

text: the

text: full

text: CFT

text: correlator.

text: The

text: individual

text: B

text: (s,

text: t)

text: do

text: not

text: fall

text: oﬀ

text: exponentially

text: as

text: s,

text: t

text: ±i∞,

text: since

text: the

text: Virasoro

text: blocks

text: are

text: w

text: not

text: analytic

text: near

text: w

text: But

text: if

text: the

text: sum

text: of

text: the

text: B

text: (s,

text: t)

text: has

text: a

text: good

text: asymptotic

text: behavior,

text: w

text: then

text: the

text: full

text: CFT

text: correlator

text: will

text: be

text: thermal.

text: One

text: might

text: also

text: investigate

text: factorizations

text: as

text: in

text: equation

text: in

text: this

text: Mellin

text: space

text: language.

label: section

text: Future

text: directions

text: Intuition

text: suggests

text: that

text: CFT

text: operators

text: carrying

text: a

text: large

text: conserved

text: charge

text: may

text: generate

text: a

text: classical

text: background

text: ﬁeld

text: aﬀecting

text: correlation

text: functions

text: in

text: a

text: universal

text: way.

text: This

text: idea

text: has

text: obvious

text: validity

text: in

text: the

text: case

text: of

text: AdS/CFT,

text: where

text: heavy

text: or

text: charged

text: states

text: generate

text: gravitational

text: or

text: gauge

text: ﬁelds

text: in

text: AdS,

text: but

text: one

text: can

text: also

text: look

text: for

text: manifestations

text: of

text: this

text: eﬀect

text: in

text: general

text: CFTs.

text: We

text: have

text: shown

text: that

text: heavy

text: operators

text: in

text: CFTs

text: have

text: exactly

text: this

text: eﬀect,

text: and

text: that

text: it

text: can

text: be

text: used

text: to

text: compute

text: Virasoro

text: conformal

text: blocks

text: at

text: large

text: central

text: charge.

text: We

text: also

text: used

text: this

text: idea

text: to

text: sum

text: up

text: contributions

text: from

text: currents

text: in

text: the

text: CFT.

text: Classical

text: gravitational

text: and

text: gauge

text: ﬁelds

text: in

text: AdS

text: have

text: a

text: universal

text: manifestation

text: in

text: all

text: CFT

text: at

text: large

text: central

text: charge.

text: To

text: leading

text: order

text: at

text: large

text: central

text: charge

text: c,

text: the

text: heavy-light

text: Virasoro

text: blocks

text: bear

text: a

text: striking

text: imprint

text: of

text: thermality,

text: and

text: it

text: would

text: be

text: interesting

text: to

text: explore

text: this

text: property

text: in

text: more

text: detail.

text: In

text: particular,

text: one

text: should

text: expect

text: that

text: the

text: probability

text: of

text: a

text: transition

text: from

text: one

text: heavy

text: state

text: to

text: another

text: should

text: be

text: weighted

text: by

text: a

text: Boltzmann

text: factor.

text: The

text: rescaled

text: δH

text: appearing

text: α

text: TH

text: in

text: the

text: conformal

text: blocks

text: of

text: equation

text: seems

text: tantalizing

text: in

text: this

text: regard.

text: In

text: fact,

text: in

text: the

text: limit

text: of

text: small

text: h,

text: δL

text: the

text: conformal

text: blocks

text: approach

text: a

text: universal

text: form

text: proportional

text: to

text: w)δH/α.

text: This

text: result

text: might

text: be

text: used

text: to

text: argue

text: that

text: the

text: rates

text: for

text: transitions

text: among

text: the

text: heavy

text: states

text: take

text: a

text: universal

text: thermal

text: form.

text: Unitary

text: CFT

text: correlators

text: should

text: not

text: be

text: exactly

text: thermal.

text: One

text: can

text: use

text: the

text: recursion

text: relations

text: of

text: section

text: to

text: compute

text: corrections

text: to

text: our

text: c

text: result,

text: but

text: at

text: present

text: this

text: is

text: only

text: practical

text: if

text: we

text: work

text: to

text: low

text: order

text: in

text: the

text: coordinate

text: w,

text: or

text: perhaps

text: to

text: ﬁrst

text: order

text: in

text: However,

text: corrections

text: to

text: thermality

text: are

text: most

text: likely

text: non-perturbative

text: in

text: c,

text: showing

text: up

text: in

text: the

text: Virasoro

text: blocks

text: at

text: ﬁnite

text: z

text: or

text: w.

text: It

text: would

text: be

text: very

text: exciting

text: to

text: understand

text: these

text: non-perturbative

text: corrections.

text: CFT

text: correlators

text: are

text: made

text: from

text: an

text: inﬁnite

text: sum

text: of

text: Virasoro

text: blocks,

text: so

text: it

text: would

text: also

text: be

text: interesting

text: to

text: understand

text: whether

text: corrections

text: to

text: thermality

text: arise

text: primarily

text: from

text: non-

text: perturbative

text: corrections

text: to

text: the

text: individual

text: Virasoro

text: blocks,

text: or

text: from

text: patterns

text: in

text: the

text: inﬁnite

text: sum.

text: An

text: immediate

text: question

text: is

text: whether

text: one

text: can

text: obtain

text: similar

text: results

text: using

text: classical

text: back-

text: ground

text: ﬁelds

text: for

text: CFTs

text: in

text: d

text: dimensions.

text: We

text: were

text: able

text: to

text: obtain

text: very

text: precise

text: results

text: for

text: CFT

text: by

text: making

text: use

text: of

text: the

text: inﬁnite

text: dimensional

text: Virasoro

text: algebra,

text: so

text: one

text: might

text: not

text: expect

text: higher

text: dimensional

text: generalizations

text: to

text: be

text: possible.

text: However,

text: we

text: believe

text: that

text: the

text: results

text: of

text: on

text: the

text: expectation

text: value

text: of

text: the

text: stress-tensor

text: in

text: conformally

text: ﬂat

text: backgrounds

text: can

text: be

text: used

text: to

text: study

text: heavy

text: operators

text: in

text: large

text: central

text: charge

text: CFTs

text: in

text: d

text: and

text: perhaps

text: after

text: imposing

text: some

text: physical

text: constraints

text: on

text: the

text: CFT

text: data.

text: It

text: would

text: be

text: very

text: interesting

text: to

text: generalize

text: the

text: analysis

text: of

text: and

text: to

text: understand

text: which

text: CFT

text: data

text: aﬀect

text: the

text: result.

text: Our

text: analysis

text: motivates

text: studying

text: CFTs

text: in

text: a

text: non-trivial

text: background

text: metric

text: chosen

text: to

text: ##LTLine##

text: ##LTLine##


text: trivialize stress tensor correlators. We have worked with a pure CFT, but one might also consider a CFT with a UV cutoﬀ, or a general local QFT. By recapitulating the computations of section in a CFT with a UV cutoﬀ, one might attempt to derive the bulk Einstein equations. The idea would be to identify the cutoﬀ with the position of a ‘UV brane’, and determine an appropriate metric as a function of the cutoﬀ. Perhaps one could obtain a more precise understanding of the relationship between UV cutoﬀ schemes and bulk locality. There is also a fascinating connection between conformal blocks and entanglement entropy at large central charge [28] which has recently led to increasingly rich matching of such eﬀects between gravity and ﬁeld theory computations [29, 31–33, 35, 37]. We have discussed how an extension to entanglement entropies of multiple intervals in the background of an excited state follows naturally from the results here, and it would be interesting to consider connections to other deformations as well. For instance, the addition of light states in the gravity theory produces quantum corrections to the Ryu-Takayanagi formula [65–67], and in terms of the ﬁeld theory these should involve conformal blocks for states with corresponding conformal weights; it would be interesting to investigate the precise decomposition. Finally, even within the pure gravitational theory, loop corrections to Renyi entropies on the gravity side are reproduced by conformal blocks including not just Virasoro descendants of the vacuum but also additional descendants that arise from acting with operators from the diﬀerent “replicas” [32, 33]. It seems natural to think of these contributions as descendants of the vacuum under an enhanced symmetry, and to try to simplify the ﬁeld theory computation using some of the methods employed here. It would be interesting to study more general background ﬁeld conﬁgurations, and cou- plings that source more general CFT operators. One can also use the methods of section to ﬁnd more complicated background metrics that simplify stress tensor correlators in the presence of more than two heavy operators, for instance by combining global conformal trans- formations with repeated application of z → zα. Such conformal mappings can be used to study states created by several heavy operators. Supersymmetric theories and higher spin conserved currents would also be of interest, and our methods could provide interesting cor- rections to the results of [68] on conformal blocks in theories with W symmetry. N Acknowledgments We would like to thank Chris Brust, Liang Dai, Tom Faulkner, Shamit Kachru, Ami Katz, Zuhair Khandker, Logan Maingi, Gustavo Marques Tavares, Junpu Wang, and Xi Dong for valuable discussions. JK is supported in part by NSF grant PHY-1316665 and by a Sloan Foundation fellowship. ALF was partially supported by ERC grant BSMOXFORD no. 228169. MTW was supported by NSF grant PHY-1214000 and DOE grant DE-SC0010025. A Details of recursion formula In this appendix we will present explicit formulas necessary for the evaluation of the recursion formula, which were ﬁrst derived in [45, 46]. Instead of using the central charge c, – 27 –

text: trivialize

text: stress

text: tensor

text: correlators.

text: We

text: have

text: worked

text: with

text: a

text: pure

text: CFT,

text: but

text: one

text: might

text: also

text: consider

text: a

text: CFT

text: with

text: a

text: UV

text: cutoﬀ,

text: or

text: a

text: general

text: local

text: QFT.

text: By

text: recapitulating

text: the

text: computations

text: of

text: section

text: in

text: a

text: CFT

text: with

text: a

text: UV

text: cutoﬀ,

text: one

text: might

text: attempt

text: to

text: derive

text: the

text: bulk

text: Einstein

text: equations.

text: The

text: idea

text: would

text: be

text: to

text: identify

text: the

text: cutoﬀ

text: with

text: the

text: position

text: of

text: a

text: ‘UV

text: brane’,

text: and

text: determine

text: an

text: appropriate

text: metric

text: as

text: a

text: function

text: of

text: the

text: cutoﬀ.

text: Perhaps

text: one

text: could

text: obtain

text: a

text: more

text: precise

text: understanding

text: of

text: the

text: relationship

text: between

text: UV

text: cutoﬀ

text: schemes

text: and

text: bulk

text: locality.

text: There

text: is

text: also

text: a

text: fascinating

text: connection

text: between

text: conformal

text: blocks

text: and

text: entanglement

text: entropy

text: at

text: large

text: central

text: charge

text: which

text: has

text: recently

text: led

text: to

text: increasingly

text: rich

text: matching

text: of

text: such

text: eﬀects

text: between

text: gravity

text: and

text: ﬁeld

text: theory

text: computations

text: We

text: have

text: discussed

text: how

text: an

text: extension

text: to

text: entanglement

text: entropies

text: of

text: multiple

text: intervals

text: in

text: the

text: background

text: of

text: an

text: excited

text: state

text: follows

text: naturally

text: from

text: the

text: results

text: here,

text: and

text: it

text: would

text: be

text: interesting

text: to

text: consider

text: connections

text: to

text: other

text: deformations

text: as

text: well.

text: For

text: instance,

text: the

text: addition

text: of

text: light

text: states

text: in

text: the

text: gravity

text: theory

text: produces

text: quantum

text: corrections

text: to

text: the

text: Ryu-Takayanagi

text: formula

text: and

text: in

text: terms

text: of

text: the

text: ﬁeld

text: theory

text: these

text: should

text: involve

text: conformal

text: blocks

text: for

text: states

text: with

text: corresponding

text: conformal

text: weights;

text: it

text: would

text: be

text: interesting

text: to

text: investigate

text: the

text: precise

text: decomposition.

text: Finally,

text: even

text: within

text: the

text: pure

text: gravitational

text: theory,

text: loop

text: corrections

text: to

text: Renyi

text: entropies

text: on

text: the

text: gravity

text: side

text: are

text: reproduced

text: by

text: conformal

text: blocks

text: including

text: not

text: just

text: Virasoro

text: descendants

text: of

text: the

text: vacuum

text: but

text: also

text: additional

text: descendants

text: that

text: arise

text: from

text: acting

text: with

text: operators

text: from

text: the

text: diﬀerent

text: “replicas”

text: It

text: seems

text: natural

text: to

text: think

text: of

text: these

text: contributions

text: as

text: descendants

text: of

text: the

text: vacuum

text: under

text: an

text: enhanced

text: symmetry,

text: and

text: to

text: try

text: to

text: simplify

text: the

text: ﬁeld

text: theory

text: computation

text: using

text: some

text: of

text: the

text: methods

text: employed

text: here.

text: It

text: would

text: be

text: interesting

text: to

text: study

text: more

text: general

text: background

text: ﬁeld

text: conﬁgurations,

text: and

text: cou-

text: plings

text: that

text: source

text: more

text: general

text: CFT

text: operators.

text: One

text: can

text: also

text: use

text: the

text: methods

text: of

text: section

text: to

text: ﬁnd

text: more

text: complicated

text: background

text: metrics

text: that

text: simplify

text: stress

text: tensor

text: correlators

text: in

text: the

text: presence

text: of

text: more

text: than

text: two

text: heavy

text: operators,

text: for

text: instance

text: by

text: combining

text: global

text: conformal

text: trans-

text: formations

text: with

text: repeated

text: application

text: of

text: z

text: zα.

text: Such

text: conformal

text: mappings

text: can

text: be

text: used

text: to

text: study

text: states

text: created

text: by

text: several

text: heavy

text: operators.

text: Supersymmetric

text: theories

text: and

text: higher

text: spin

text: conserved

text: currents

text: would

text: also

text: be

text: of

text: interest,

text: and

text: our

text: methods

text: could

text: provide

text: interesting

text: cor-

text: rections

text: to

text: the

text: results

text: of

text: on

text: conformal

text: blocks

text: in

text: theories

text: with

text: W

text: symmetry.

text: N

text: Acknowledgments

text: We

text: would

text: like

text: to

text: thank

text: Chris

text: Brust,

text: Liang

text: Dai,

text: Tom

text: Faulkner,

text: Shamit

text: Kachru,

text: Ami

text: Katz,

text: Zuhair

text: Khandker,

text: Logan

text: Maingi,

text: Gustavo

text: Marques

text: Tavares,

text: Junpu

text: Wang,

text: and

text: Xi

text: Dong

text: for

text: valuable

text: discussions.

text: JK

text: is

text: supported

text: in

text: part

text: by

text: NSF

text: grant

text: and

text: by

text: a

text: Sloan

text: Foundation

text: fellowship.

text: ALF

text: was

text: partially

text: supported

text: by

text: ERC

text: grant

text: BSMOXFORD

text: no.

text: MTW

text: was

text: supported

text: by

text: NSF

text: grant

text: and

text: DOE

text: grant

text: A

text: Details

text: of

text: recursion

text: formula

text: In

text: this

text: appendix

text: we

text: will

text: present

text: explicit

text: formulas

text: necessary

text: for

text: the

text: evaluation

text: of

text: the

text: recursion

text: formula,

text: which

text: were

text: ﬁrst

text: derived

text: in

text: Instead

text: of

text: using

text: the

text: central

text: charge

text: c,


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text: Spectroscopy,”

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text: and

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text: Black

text: hole

text: in

text: three-dimensional

text: space-time,”

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text: F.

text: Dolan

text: and

text: H.

text: Osborn,

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text: four

text: point

text: functions

text: and

text: the

text: operator

text: product

text: expansion,”

text: Nucl.Phys.

text: [hep-th].

text: F.

text: Dolan

text: and

text: H.

text: Osborn,

text: “Conformal

text: partial

text: waves

text: and

text: the

text: operator

text: product

text: expansion,”

text: Nucl.Phys.

text: [hep-th].

text: F.

text: Dolan

text: and

text: H.

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text: Waves:

text: Further

text: Mathematical

text: Results,”

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text: An

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text: Conformal

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text: A.

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text: Phys.Rev.

text: C.

text: P.

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text: and

text: K.-W.

text: Huang,

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text: Anomalies

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text: Theories,”

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text: Conformal

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text: current

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text: P.

text: Calabrese

text: and

text: J.

text: Cardy,

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text: theory,”

text: J.Phys.

text: [cond-mat.stat-mech].

text: J.

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text: R.

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text: Points

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text: Fitzpatrick

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text: Holographic

text: S-Matrix,”

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text: [hep-th].

text: G.

text: Mack,

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text: representation

text: of

text: Conformal

text: Field

text: Theories

text: in

text: D

text: dimensions

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text: transformation

text: to

text: auxiliary

text: Dual

text: Resonance

text: Models.

text: Scalar

text: amplitudes,”

text: [hep-th].


text: Annu. Rev. Astron. Astrophys. 2015 53 Boogert, Gerakines, & Whittet The 4.67 µm CO Band: the Most Volatile Ices . . . . . . . . . . . . . . . . . . . . . . . . 11 The 15.2 µm CO Band: Segregation and Distillation . . . . . . . . . . . . . . . . . . . . 12 2 The 6.0 and 6.85 µm Features: Complexity Revealed . . . . . . . . . . . . . . . . . . . . . 13 The Lattice Modes: Ice Structure and Emission . . . . . . . . . . . . . . . . . . . . . . . . 15 ICES ACROSS ENVIRONMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Quiescent Dense Clouds and Cores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Envelopes of Massive YSOs in the Galactic Disk . . . . . . . . . . . . . . . . . . . . . . . 16 Envelopes of Low and Intermediate Mass YSOs . . . . . . . . . . . . . . . . . . . . . . . . 17 Disks Around Low and Intermediate Mass YSOs . . . . . . . . . . . . . . . . . . . . . . . 18 Galactic Center Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Shells Surrounding Evolved Stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Massive YSOs in the Magellanic Clouds . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Other Galaxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Solar System Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 COLUMN DENSITIES AND ABUNDANCES . . . . . . . . . . . . . . . . . . . . . . 21 Identiﬁcation Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Upper Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Abundance Variations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Isotopologues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Interstellar Versus Cometary Ice Abundances . . . . . . . . . . . . . . . . . . . . . . . . . 32 Elemental Budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 GRAIN SIZE AND MANTLE THICKNESS . . . . . . . . . . . . . . . . . . . . . . . 33 CONSTRAINTS ON ICE EVOLUTION MODELS . . . . . . . . . . . . . . . . . . . . 34 Accretion and Grain Surface Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Thermal Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Energetic Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Connection with Cometary Ices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 SUMMARY POINTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 FUTURE ISSUES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 RELATED RESOURCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 1 PERSPECTIVE The condensation of gas phase elements on cold dust particles has long been con- sidered an important process in the Universe. Lindblad (1935) studied the condensa- tion of metals to form meteoritic material as the starting point of planet formation. Considering the elemental abundances, van de Hulst (1946) realized that the same (Interstellar) ice: process must lead to the formation of H O, CH , and NH ices on the grains. Chem- 2 4 3 solid state pure istry on cold grain surfaces has since emerged as a vital route to formation of new volatiles (H O, CO, molecules in dense clouds and circumstellar envelopes and disks, including species 2 etc.) or mixtures that cannot readily be formed in the gas phase (Tielens & Hagen 1982; Herbst & thereof, with, per- van Dishoeck 2009 and references therein); surface chemistry thus controls the com- haps, refractory position not only of the icy mantles but also of the molecular gas desorbed from the inclusions, located grains in the vicinity of cloud edges, shocks, and the radiation ﬁelds of Young Stellar on interstellar dust Objects (YSOs). grains. 2

text: Annu.

text: Rev.

text: Astron.

text: Astrophys.

text: Boogert,

text: Gerakines,

text: Whittet

text: The

text: µm

text: CO

text: Band:

text: the

text: Most

text: Volatile

text: Ices

text: The

text: µm

text: CO

text: Band:

text: Segregation

text: and

text: Distillation

text: The

text: and

text: µm

text: Features:

text: Complexity

text: Revealed

text: The

text: Lattice

text: Modes:

text: Ice

text: Structure

text: and

text: Emission

text: ICES

text: ACROSS

text: ENVIRONMENTS

text: Quiescent

text: Dense

text: Clouds

text: and

text: Cores

text: Envelopes

text: of

text: Massive

text: YSOs

text: in

text: the

text: Galactic

text: Disk

text: Envelopes

text: of

text: Low

text: and

text: Intermediate

text: Mass

text: YSOs

text: Disks

text: Around

text: Low

text: and

text: Intermediate

text: Mass

text: YSOs

text: Galactic

text: Center

text: Region

text: Shells

text: Surrounding

text: Evolved

text: Stars

text: Massive

text: YSOs

text: in

text: the

text: Magellanic

text: Clouds

text: Other

text: Galaxies

text: Solar

text: System

text: Objects

text: COLUMN

text: DENSITIES

text: AND

text: ABUNDANCES

text: Identiﬁcation

text: Issues

text: Upper

text: Limits

text: Abundance

text: Variations

text: Isotopologues

text: Interstellar

text: Versus

text: Cometary

text: Ice

text: Abundances

text: Elemental

text: Budget

text: GRAIN

text: SIZE

text: AND

text: MANTLE

text: THICKNESS

text: CONSTRAINTS

text: ON

text: ICE

text: EVOLUTION

text: MODELS

text: Accretion

text: and

text: Grain

text: Surface

text: Chemistry

text: Thermal

text: Processing

text: Energetic

text: Processing

text: Connection

text: with

text: Cometary

text: Ices

text: SUMMARY

text: POINTS

text: FUTURE

text: ISSUES

text: RELATED

text: RESOURCES

text: ACKNOWLEDGMENTS

text: PERSPECTIVE

text: The

text: condensation

text: of

text: gas

text: phase

text: elements

text: on

text: cold

text: dust

text: particles

text: has

text: long

text: been

text: con-

text: sidered

text: an

text: important

text: process

text: in

text: the

text: Universe.

text: Lindblad

text: studied

text: the

text: condensa-

text: tion

text: of

text: metals

text: to

text: form

text: meteoritic

text: material

text: as

text: the

text: starting

text: point

text: of

text: planet

text: formation.

text: Considering

text: the

text: elemental

text: abundances,

text: van

text: de

text: Hulst

text: realized

text: that

text: the

text: same

text: (Interstellar)

text: ice:

text: process

text: must

text: lead

text: to

text: the

text: formation

text: of

text: H

text: O,

text: CH

text: and

text: NH

text: ices

text: on

text: the

text: grains.

text: Chem-

text: solid

text: state

text: pure

text: istry

text: on

text: cold

text: grain

text: surfaces

text: has

text: since

text: emerged

text: as

text: a

text: vital

text: route

text: to

text: formation

text: of

text: new

text: volatiles

text: (H

text: O,

text: CO,

text: molecules

text: in

text: dense

text: clouds

text: and

text: circumstellar

text: envelopes

text: and

text: disks,

text: including

text: species

text: etc.)

text: or

text: mixtures

text: that

text: cannot

text: readily

text: be

text: formed

text: in

text: the

text: gas

text: phase

text: (Tielens

text: Hagen

text: Herbst

text: thereof,

text: with,

text: per-

text: van

text: Dishoeck

text: and

text: references

text: therein);

text: surface

text: chemistry

text: thus

text: controls

text: the

text: com-

text: haps,

text: refractory

text: position

text: not

text: only

text: of

text: the

text: icy

text: mantles

text: but

text: also

text: of

text: the

text: molecular

text: gas

text: desorbed

text: from

text: the

text: inclusions,

text: located

text: grains

text: in

text: the

text: vicinity

text: of

text: cloud

text: edges,

text: shocks,

text: and

text: the

text: radiation

text: ﬁelds

text: of

text: Young

text: Stellar

text: on

text: interstellar

text: dust

text: Objects

text: (YSOs).

text: grains.


text: 18 Boogert, Gerakines, & Whittet al., 1998), has eﬀectively the same formation threshold as H O (Bergin et al., 2005; 2 Whittet et al., 2009), showing a close chemical connection between these species. § Monolayer: one Still, their relative abundances vary by up to a factor of three ( ). Freeze-out of the ∼ layer of molecules more volatile CO species occurs deeper into the cloud, at 3 mag (Taurus, Serpens; covering dust grain Fig. 7; Chiar et al. 1995). Kerr et al. (1993) determine a three times larger threshold surfaces, for H O in Ophiuchus, but along individual lines of sight, values are lower, probably due to 2 corresponding to clumpiness (Shuping et al., 2000). CH OH ice forms at even greater cloud depths ± 3 1015 molecules/cm2 (9 3 mag; Boogert et al. 2011; Chiar et al. 2011; Whittet et al. 2011b), consistent § and an abundance with the formation requirement of “catastrophic” CO freeze out ( ). This is reﬂected ∼ × − X few 10 6. in large CH OH abundance variations, from less than 3% in Taurus (Chiar et al., H 3 1996) to 12% in some isolated dense cores (Boogert et al., 2011; Chiar et al., 2011). A general characteristic is the pristine nature of the ices in these environments: the dominance of amorphous H O (Smith et al., 1993), the large contribution of 2 apolar ices to the CO band (Whittet et al., 1985), and the absence of segregated (heated) CO ices (Whittet et al., 2009). The peak position of the 6.85 µm feature 2 is also consistent with unprocessed ices (Knez et al., 2005; Boogert et al., 2011). The absence of the 4.62 µm “XCN” feature (Whittet et al., 1985; Noble et al., 2013) is sometimes interpreted as a lack of processing, but, more likely, it is related to § § insuﬃcient CO freeze-out ( and ). 5.2 Envelopes of Massive YSOs in the Galactic Disk ∼ A sample of 20 MYSOs (luminosities above 104 L(cid:12), masses above 10 M(cid:12)) in the Galactic Disk has been studied extensively in the ice features, using mostly data from ISO. We refer to reviews by Gibb et al. (2004), Boogert & Ehrenfreund (2004b), and Dartois (2005) for historical work. Few new observations of these objects have been published since the launch of Spitzer Space Telescope in 2003, but the earlier data have been re-analyzed with new methods or included as comparison objects with LYSOs in later work (Pontoppidan et al., 2008; Boogert et al., 2008). MYSOs § in the GC region are discussed in . The evidence for thermal processing of the MYSO ices is ubiquitous in all the § tracers discussed in . This is mostly based on observations along a single line of sight toward the central object, but ice maps have conﬁrmed it. Using extended scattered light as a background source, the 3.0 µm band is deep toward a disk- like structure around the MYSO AFGL 2136, but the ice abundance is suppressed relative to the surrounding cloud (Holbrook & Temi, 1998), probably as a result of sublimation. Similar conclusions were drawn for ice maps toward the MYSO S140 IRS1 (Harker et al., 1997). 5.3 Envelopes of Low and Intermediate Mass YSOs As the link between quiescent clouds and protoplanetary disks that give birth to potentially life-bearing planetary systems, ices in the envelopes of LYSOs are of paramount importance. The ﬁrst (3.0 µm) ice band toward an LYSO was detected by Cohen (1975) toward HL Tau and it was thought to originate in an edge-on disk (Cohen, 1983), but a location in the envelope is more likely (Furlan et al., 2008). This demonstrates the diﬃculty of locating ices along the line of sight (Boogert et al., 2002c). Here, surveys of ices most likely located in envelopes around LYSOs are § reviewed, while disk studies are reviewed in .

text: Boogert,

text: Gerakines,

text: Whittet

text: al.,

text: has

text: eﬀectively

text: the

text: same

text: formation

text: threshold

text: as

text: H

text: O

text: (Bergin

text: et

text: al.,

text: Whittet

text: et

text: al.,

text: showing

text: a

text: close

text: chemical

text: connection

text: between

text: these

text: species.

text: Monolayer:

text: one

text: Still,

text: their

text: relative

text: abundances

text: vary

text: by

text: up

text: to

text: a

text: factor

text: of

text: three

text: Freeze-out

text: of

text: the

text: layer

text: of

text: molecules

text: more

text: volatile

text: CO

text: species

text: occurs

text: deeper

text: into

text: the

text: cloud,

text: at

text: mag

text: (Taurus,

text: Serpens;

text: covering

text: dust

text: grain

text: Fig.

text: Chiar

text: et

text: al.

text: Kerr

text: et

text: al.

text: determine

text: a

text: three

text: times

text: larger

text: threshold

text: surfaces,

text: for

text: H

text: O

text: in

text: Ophiuchus,

text: but

text: along

text: individual

text: lines

text: of

text: sight,

text: values

text: are

text: lower,

text: probably

text: due

text: to

text: corresponding

text: to

text: clumpiness

text: (Shuping

text: et

text: al.,

text: CH

text: OH

text: ice

text: forms

text: at

text: even

text: greater

text: cloud

text: depths

text: mag;

text: Boogert

text: et

text: al.

text: Chiar

text: et

text: al.

text: Whittet

text: et

text: al.

text: consistent

text: and

text: an

text: abundance

text: with

text: the

text: formation

text: requirement

text: of

text: “catastrophic”

text: CO

text: freeze

text: out

text: This

text: is

text: reﬂected

text: X

text: few

text: in

text: large

text: CH

text: OH

text: abundance

text: variations,

text: from

text: less

text: than

text: in

text: Taurus

text: (Chiar

text: et

text: al.,

text: H

text: to

text: in

text: some

text: isolated

text: dense

text: cores

text: (Boogert

text: et

text: al.,

text: Chiar

text: et

text: al.,

text: A

text: general

text: characteristic

text: is

text: the

text: pristine

text: nature

text: of

text: the

text: ices

text: in

text: these

text: environments:

text: the

text: dominance

text: of

text: amorphous

text: H

text: O

text: (Smith

text: et

text: al.,

text: the

text: large

text: contribution

text: of

text: apolar

text: ices

text: to

text: the

text: CO

text: band

text: (Whittet

text: et

text: al.,

text: and

text: the

text: absence

text: of

text: segregated

text: (heated)

text: CO

text: ices

text: (Whittet

text: et

text: al.,

text: The

text: peak

text: position

text: of

text: the

text: µm

text: feature

text: is

text: also

text: consistent

text: with

text: unprocessed

text: ices

text: (Knez

text: et

text: al.,

text: Boogert

text: et

text: al.,

text: The

text: absence

text: of

text: the

text: µm

text: “XCN”

text: feature

text: (Whittet

text: et

text: al.,

text: Noble

text: et

text: al.,

text: is

text: sometimes

text: interpreted

text: as

text: a

text: lack

text: of

text: processing,

text: but,

text: more

text: likely,

text: it

text: is

text: related

text: to

text: insuﬃcient

text: CO

text: freeze-out

text: and

text: Envelopes

text: of

text: Massive

text: YSOs

text: in

text: the

text: Galactic

text: Disk

text: A

text: sample

text: of

text: MYSOs

text: (luminosities

text: above

text: masses

text: above

text: in

text: the

text: Galactic

text: Disk

text: has

text: been

text: studied

text: extensively

text: in

text: the

text: ice

text: features,

text: using

text: mostly

text: data

text: from

text: ISO.

text: We

text: refer

text: to

text: reviews

text: by

text: Gibb

text: et

text: al.

text: Boogert

text: Ehrenfreund

text: and

text: Dartois

text: for

text: historical

text: work.

text: Few

text: new

text: observations

text: of

text: these

text: objects

text: have

text: been

text: published

text: since

text: the

text: launch

text: of

text: Spitzer

text: Space

text: Telescope

text: in

text: but

text: the

text: earlier

text: data

text: have

text: been

text: re-analyzed

text: with

text: new

text: methods

text: or

text: included

text: as

text: comparison

text: objects

text: with

text: LYSOs

text: in

text: later

text: work

text: (Pontoppidan

text: et

text: al.,

text: Boogert

text: et

text: al.,

text: MYSOs

text: in

text: the

text: GC

text: region

text: are

text: discussed

text: in

text: The

text: evidence

text: for

text: thermal

text: processing

text: of

text: the

text: MYSO

text: ices

text: is

text: ubiquitous

text: in

text: all

text: the

text: tracers

text: discussed

text: in

text: This

text: is

text: mostly

text: based

text: on

text: observations

text: along

text: a

text: single

text: line

text: of

text: sight

text: toward

text: the

text: central

text: object,

text: but

text: ice

text: maps

text: have

text: conﬁrmed

text: it.

text: Using

text: extended

text: scattered

text: light

text: as

text: a

text: background

text: source,

text: the

text: µm

text: band

text: is

text: deep

text: toward

text: a

text: disk-

text: like

text: structure

text: around

text: the

text: MYSO

text: AFGL

text: but

text: the

text: ice

text: abundance

text: is

text: suppressed

text: relative

text: to

text: the

text: surrounding

text: cloud

text: (Holbrook

text: Temi,

text: probably

text: as

text: a

text: result

text: of

text: sublimation.

text: Similar

text: conclusions

text: were

text: drawn

text: for

text: ice

text: maps

text: toward

text: the

text: MYSO

text: (Harker

text: et

text: al.,

text: Envelopes

text: of

text: Low

text: and

text: Intermediate

text: Mass

text: YSOs

text: As

text: the

text: link

text: between

text: quiescent

text: clouds

text: and

text: protoplanetary

text: disks

text: that

text: give

text: birth

text: to

text: potentially

text: life-bearing

text: planetary

text: systems,

text: ices

text: in

text: the

text: envelopes

text: of

text: LYSOs

text: are

text: of

text: paramount

text: importance.

text: The

text: ﬁrst

text: µm)

text: ice

text: band

text: toward

text: an

text: LYSO

text: was

text: detected

text: by

text: Cohen

text: toward

text: HL

text: Tau

text: and

text: it

text: was

text: thought

text: to

text: originate

text: in

text: an

text: edge-on

text: disk

text: (Cohen,

text: but

text: a

text: location

text: in

text: the

text: envelope

text: is

text: more

text: likely

text: (Furlan

text: et

text: al.,

text: This

text: demonstrates

text: the

text: diﬃculty

text: of

text: locating

text: ices

text: along

text: the

text: line

text: of

text: sight

text: (Boogert

text: et

text: al.,

text: Here,

text: surveys

text: of

text: ices

text: most

text: likely

text: located

text: in

text: envelopes

text: around

text: LYSOs

text: are

text: reviewed,

text: while

text: disk

text: studies

text: are

text: reviewed

text: in


text: − ]6 01[ bX ]%[ aX seicepS H O2H csratS GB sOSYL sOSYM stemoC csratS GB sOSYL sOSYM − )41.0( 82.081.0 )5.0( 7.05.0 j OOCH ∼ 21.0 ∼ 5.0 8.0< 2.0 24.0-)01.0 <( 1.0< 4.0 0.1-3.0 × − × − 11 ) OOCH( X 11 ) OOCH( X jOHC HC H O2H 3 9.48.3 8.56.4 4.51.4 118 5111 3111 +HN 9.2 2.3 8.1 6 7 9 4 6.9-9.1 21-8.0 0.6-4.1 31-4 52-4 43-9 ∼ ≤ ∼ 80.0 4.0 2.0 2.0 4.1-)9.0 <( OS ∼ ∼ 2 1 8 kHAP naidem eht sevig wor tsrﬁ eht ,elucelom hcae roF .ytisned nmuloc eci O H eht ot evitaler secnadnubA a 2 .stimil reppu gnidulcni naidem eht stekcarb ni dna ,snoitceted eht fo seulav elitrauq reppu dna rewol dna eeS .egnar lluf eht swohs ti ,nevig si wor eno ylno fI .secnadnuba fo egnar lluf eht sevig wor dnoces ehT § .secnerefer rof dna 1 elbaT . N ot evitaler secnadnuba rof tub ,nmuloc X eht ni sA b H O2H .seroc dna sduolc tnecseiuQ c .artceps ytilauq hgih ni seugolopotosi ro sedom elpitlum no desab deﬁitnedI d § .) ( deﬁitnedi ylbissop saw ODH dna ,deﬁitnedi yleruces osla erew OC31 dna OC31 seugolopotosi ehT e 2 .)2002 ,.la te siotraD( serutaef elpitlum fo sisylana suoenatlumis eht morf devired seulaV f .artceps yrotarobal sehctam elﬁorp eht dna erutaef noitprosba elgnis a no desab noitacﬁitnedI g si artceps yrotarobal ot hctam gnicnivnoc on dna erutaef noitprosba elgnis a no desab noitacﬁitnedI h .elbaliava te grebO¨ ;9991 ,.la te ettuhcS( dnab eci mµ 42.7 eht fo sreirrac eb yam HO HC HC ro/dna HOOCH i 2 3 .)1102 ,.la − .)9991 ,.la te ettuhcS( dnab eci mµ 14.7 eht fo sreirrac eb yam OHC HC ro/dna OOCH j 3 HAP hcae gnimussa dna )4102( .la te namllU-eergedraH ni devired sdnob C-C fo ytisned nmuloc gnisU k .smota nobrac 05 sniatnoc seiceps 26 Boogert, Gerakines, & Whittet ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine## ##LTLine##

text: bX

text: aX

text: seicepS

text: H

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text: GB

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text: j

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text: X

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text: X

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text: Observations of the Icy Universe; ARAA 53 (2015; accepted), v. 05/05/2015 29 et al., 2008), the laboratory proﬁle is too broad in H O ices (G´alvez et al., 2010). 2 After H O ice sublimation, a better ﬁt is obtained, and at even higher temperature 2 the peak position shifts to longer wavelengths, consistent with observations of YSOs § (enhanced C4/C3 component ratios; ). Finally, a very broad absorption observed § toward a number of YSOs (C5 component; ) has been ascribed to salts (Schutte & Khanna, 2003) and organic residue (Gibb & Whittet, 2002), both of which are ener- getic and/or thermal processing products, but these identiﬁcations need independent spectroscopic conﬁrmation. The 7.24 µm (HCOOH?) feature. This feature was attributed to the C- H deformation mode in HCOOH, and speciﬁc mixtures containing both H O and 2 CH OH are needed to match the peak position and proﬁle (Schutte et al., 1999). The 3 depth is consistent with the much stronger C=O stretch mode at 5.85 µm (Schutte et al., 1996), but its identiﬁcation was put into question because of issues with the baseline in the laboratory spectra (Boogert et al., 2008; O¨ berg et al., 2011) and an abundance that is a factor of 104 larger compared to the gas phase in hot cores is also not understood (Bisschop et al., 2007). O¨ berg et al. (2011) propose pure ethanol instead. Other species tend to have slightly blue-shifted peak positions (HCONH , 2 C H ; Schutte et al. 1999; NH CH OH; Bossa et al. 2009) and are listed in Table 3. 5 12 2 2 6.2 Upper Limits Table 3 shows abundance upper limits of astrophysically relevant species. These were determined by comparing laboratory spectra with the spectra of YSOs and background stars, taking into account position and proﬁle dependencies on the ice composition. For symmetric species (in particular O , N , and H ), interactions 2 2 2 in the ice matrix induce a dipole moment, and the band strength is a very strong function of molecular environment. These make the derived abundance upper limits uncertain. Indirect measurements of the O and N abundances in mixtures with 2 2 CO by the eﬀect on the 12CO (Elsila et al., 1997) and 13CO (Boogert et al., 2002a) ∼ band proﬁles lower the upper limits for N by a factor of 5, but do not further 2 constrain those of O . The case of H refers to energetically processed ices that are 2 2 able to retain the produced H (Sandford et al., 1993). In pure form H sublimates 2 2 at 3 K, well below the temperature of dense clouds. An upper limit rather than the detection claimed in Sandford et al. (1993) is quoted because of confusion with photospheric absorption lines at 2.415 µm.

text: Observations

text: of

text: the

text: Icy

text: Universe;

text: ARAA

text: accepted),

text: v.

text: et

text: al.,

text: the

text: laboratory

text: proﬁle

text: is

text: too

text: broad

text: in

text: H

text: O

text: ices

text: (G´alvez

text: et

text: al.,

text: After

text: H

text: O

text: ice

text: sublimation,

text: a

text: better

text: ﬁt

text: is

text: obtained,

text: and

text: at

text: even

text: higher

text: temperature

text: the

text: peak

text: position

text: shifts

text: to

text: longer

text: wavelengths,

text: consistent

text: with

text: observations

text: of

text: YSOs

text: (enhanced

text: component

text: ratios;

text: Finally,

text: a

text: very

text: broad

text: absorption

text: observed

text: toward

text: a

text: number

text: of

text: YSOs

text: component;

text: has

text: been

text: ascribed

text: to

text: salts

text: (Schutte

text: Khanna,

text: and

text: organic

text: residue

text: (Gibb

text: Whittet,

text: both

text: of

text: which

text: are

text: ener-

text: getic

text: and/or

text: thermal

text: processing

text: products,

text: but

text: these

text: identiﬁcations

text: need

text: independent

text: spectroscopic

text: conﬁrmation.

text: The

text: µm

text: (HCOOH?)

text: feature.

text: This

text: feature

text: was

text: attributed

text: to

text: the

text: C-

text: H

text: deformation

text: mode

text: in

text: HCOOH,

text: and

text: speciﬁc

text: mixtures

text: containing

text: both

text: H

text: O

text: and

text: CH

text: OH

text: are

text: needed

text: to

text: match

text: the

text: peak

text: position

text: and

text: proﬁle

text: (Schutte

text: et

text: al.,

text: The

text: depth

text: is

text: consistent

text: with

text: the

text: much

text: stronger

text: C=O

text: stretch

text: mode

text: at

text: µm

text: (Schutte

text: et

text: al.,

text: but

text: its

text: identiﬁcation

text: was

text: put

text: into

text: question

text: because

text: of

text: issues

text: with

text: the

text: baseline

text: in

text: the

text: laboratory

text: spectra

text: (Boogert

text: et

text: al.,

text: O¨

text: berg

text: et

text: al.,

text: and

text: an

text: abundance

text: that

text: is

text: a

text: factor

text: of

text: larger

text: compared

text: to

text: the

text: gas

text: phase

text: in

text: hot

text: cores

text: is

text: also

text: not

text: understood

text: (Bisschop

text: et

text: al.,

text: O¨

text: berg

text: et

text: al.

text: propose

text: pure

text: ethanol

text: instead.

text: Other

text: species

text: tend

text: to

text: have

text: slightly

text: blue-shifted

text: peak

text: positions

text: (HCONH

text: C

text: H

text: Schutte

text: et

text: al.

text: NH

text: CH

text: OH;

text: Bossa

text: et

text: al.

text: and

text: are

text: listed

text: in

text: Table

text: Upper

text: Limits

text: Table

text: shows

text: abundance

text: upper

text: limits

text: of

text: astrophysically

text: relevant

text: species.

text: These

text: were

text: determined

text: by

text: comparing

text: laboratory

text: spectra

text: with

text: the

text: spectra

text: of

text: YSOs

text: and

text: background

text: stars,

text: taking

text: into

text: account

text: position

text: and

text: proﬁle

text: dependencies

text: on

text: the

text: ice

text: composition.

text: For

text: symmetric

text: species

text: (in

text: particular

text: O

text: N

text: and

text: H

text: interactions

text: in

text: the

text: ice

text: matrix

text: induce

text: a

text: dipole

text: moment,

text: and

text: the

text: band

text: strength

text: is

text: a

text: very

text: strong

text: function

text: of

text: molecular

text: environment.

text: These

text: make

text: the

text: derived

text: abundance

text: upper

text: limits

text: uncertain.

text: Indirect

text: measurements

text: of

text: the

text: O

text: and

text: N

text: abundances

text: in

text: mixtures

text: with

text: CO

text: by

text: the

text: eﬀect

text: on

text: the

text: (Elsila

text: et

text: al.,

text: and

text: (Boogert

text: et

text: al.,

text: band

text: proﬁles

text: lower

text: the

text: upper

text: limits

text: for

text: N

text: by

text: a

text: factor

text: of

text: but

text: do

text: not

text: further

text: constrain

text: those

text: of

text: O

text: The

text: case

text: of

text: H

text: refers

text: to

text: energetically

text: processed

text: ices

text: that

text: are

text: able

text: to

text: retain

text: the

text: produced

text: H

text: (Sandford

text: et

text: al.,

text: In

text: pure

text: form

text: H

text: sublimates

text: at

text: K,

text: well

text: below

text: the

text: temperature

text: of

text: dense

text: clouds.

text: An

text: upper

text: limit

text: rather

text: than

text: the

text: detection

text: claimed

text: in

text: Sandford

text: et

text: al.

text: is

text: quoted

text: because

text: of

text: confusion

text: with

text: photospheric

text: absorption

text: lines

text: at

text: µm.


text: 36 Boogert, Gerakines, & Whittet Also, in models satisfying all observational constraints (grain size distribution, ele- mental budget, ice band proﬁles) Smith et al. (1993) ﬁnd that their observations of the 3.0 µm proﬁle in Taurus can only be explained if ice mantles are preferentially present on speciﬁc grain populations (e.g., on larger grains or on silicate grains). Indirect evidence for a distinct population of much larger, micron-sized icy grains comes from diﬀuse scattered light observed toward dense cloud cores (“coreshine”; Andersen et al. 2014). Such grains were also suggested as an alternative explanation § of the long-wavelength wing of the 4.67 µm CO ice band ( ; Dartois 2006). Large § grains have been suggested as a source of the “missing” oxygen ( ; Jenkins 2009), because for radii larger than a few micron, the infrared absorption proﬁles become too wide and shallow to be detected. In light of the small variations of the 3.0 µm § band proﬁle ( ), these suggestions need further study, including an assessment of the eﬀects of grain coagulation on the band proﬁles. 8 CONSTRAINTS ON ICE EVOLUTION MODELS The commonalities and diﬀerences in the ice abundances and band proﬁles ob- served over a wide range of environments provide strong constraints on models of ice formation and evolution. We do not review the models here, but rather summarize the observational constraints. Figure 10 illustrates the probable scenario. 8.1 Accretion and Grain Surface Chemistry The observed ice abundances are generally in good agreement with models of accretion from the gas phase followed by grain surface chemistry. In particular, the eﬃciency of hydrogenation as a result of the mobility and tunneling capacity of H atoms (e.g., Tielens & Hagen 1982) is conﬁrmed by the observations. The dominance of H O ice and mixtures with H O in all Galactic and extragalactic environments 2 2 points to a phase of molecule formation on cold grain surfaces at which the accreting ≥ − gas is atomic H- and O-rich. This is a phase of relatively low densities (n 103 cm 3) early in the cloud evolution (H/H ratios decrease rapidly with density; Hollenbach 2 et al. 1971). The ice formation threshold of A =1.6 mag near local cloud edges is V understood as the onset of rapid ice mantle growth after a monolayer has formed and the eﬀect of photodesorption decreases with increasing extinction by dust into ∝ the cloud (A ln(G /n); Hollenbach et al. 2009). This phase also includes the V 0 formation of CH , CO (polar component, likely via CO+OH; Ioppolo et al. 2011), 4 2 and NH which are all intimately mixed with H O. Variations in CO /H O ratios in 3 2 2 2 this early phase reﬂect variations of the CO accretion rates. On one hand, if the gas phase formation of CO is incomplete, e.g., at low extinctions, more O can be included in H O (Whittet et al., 2009; O¨ berg et al., 2011). It may explain the possibly CO - 2 2 free region in the SMC (Oliveira et al., 2013) and CH -rich region in Galactic cloud 4 edges (O¨ berg et al., 2011). On the other hand, CO accretion rates increase at lower temperatures and at higher densities, leading to enhanced formation of CO (up 2 to a factor of 2), still well mixed with the co-formed H O species. This phase is 2 CH OH-poor and has a relatively low CO freeze out (< 50%). At the same time, the 3 presence of the 6.85 µm feature and some absorption underlying the 6.0 µm band (Fig. 6) show that these early ices are already quite complex. They are formed on ∼ − a short time scale (109/n 105 yr at n = 104 cm 3; e.g., Hollenbach et al. 2009) ∼ compared to the cloud life time ( 107 yr) and compared to the formation time of § new species by interstellar CRs or CR-induced UV ﬁelds ( ).

text: Boogert,

text: Gerakines,

text: Whittet

text: Also,

text: in

text: models

text: satisfying

text: all

text: observational

text: constraints

text: (grain

text: size

text: distribution,

text: ele-

text: mental

text: budget,

text: ice

text: band

text: proﬁles)

text: Smith

text: et

text: al.

text: ﬁnd

text: that

text: their

text: observations

text: of

text: the

text: µm

text: proﬁle

text: in

text: Taurus

text: can

text: only

text: be

text: explained

text: if

text: ice

text: mantles

text: are

text: preferentially

text: present

text: on

text: speciﬁc

text: grain

text: populations

text: (e.g.,

text: on

text: larger

text: grains

text: or

text: on

text: silicate

text: grains).

text: Indirect

text: evidence

text: for

text: a

text: distinct

text: population

text: of

text: much

text: larger,

text: micron-sized

text: icy

text: grains

text: comes

text: from

text: diﬀuse

text: scattered

text: light

text: observed

text: toward

text: dense

text: cloud

text: cores

text: (“coreshine”;

text: Andersen

text: et

text: al.

text: Such

text: grains

text: were

text: also

text: suggested

text: as

text: an

text: alternative

text: explanation

text: of

text: the

text: long-wavelength

text: wing

text: of

text: the

text: µm

text: CO

text: ice

text: band

text: Dartois

text: Large

text: grains

text: have

text: been

text: suggested

text: as

text: a

text: source

text: of

text: the

text: “missing”

text: oxygen

text: Jenkins

text: because

text: for

text: radii

text: larger

text: than

text: a

text: few

text: micron,

text: the

text: infrared

text: absorption

text: proﬁles

text: become

text: too

text: wide

text: and

text: shallow

text: to

text: be

text: detected.

text: In

text: light

text: of

text: the

text: small

text: variations

text: of

text: the

text: µm

text: band

text: proﬁle

text: these

text: suggestions

text: need

text: further

text: study,

text: including

text: an

text: assessment

text: of

text: the

text: eﬀects

text: of

text: grain

text: coagulation

text: on

text: the

text: band

text: proﬁles.

text: CONSTRAINTS

text: ON

text: ICE

text: EVOLUTION

text: MODELS

text: The

text: commonalities

text: and

text: diﬀerences

text: in

text: the

text: ice

text: abundances

text: and

text: band

text: proﬁles

text: ob-

text: served

text: over

text: a

text: wide

text: range

text: of

text: environments

text: provide

text: strong

text: constraints

text: on

text: models

text: of

text: ice

text: formation

text: and

text: evolution.

text: We

text: do

text: not

text: review

text: the

text: models

text: here,

text: but

text: rather

text: summarize

text: the

text: observational

text: constraints.

text: Figure

text: illustrates

text: the

text: probable

text: scenario.

text: Accretion

text: and

text: Grain

text: Surface

text: Chemistry

text: The

text: observed

text: ice

text: abundances

text: are

text: generally

text: in

text: good

text: agreement

text: with

text: models

text: of

text: accretion

text: from

text: the

text: gas

text: phase

text: followed

text: by

text: grain

text: surface

text: chemistry.

text: In

text: particular,

text: the

text: eﬃciency

text: of

text: hydrogenation

text: as

text: a

text: result

text: of

text: the

text: mobility

text: and

text: tunneling

text: capacity

text: of

text: H

text: atoms

text: (e.g.,

text: Tielens

text: Hagen

text: is

text: conﬁrmed

text: by

text: the

text: observations.

text: The

text: dominance

text: of

text: H

text: O

text: ice

text: and

text: mixtures

text: with

text: H

text: O

text: in

text: all

text: Galactic

text: and

text: extragalactic

text: environments

text: points

text: to

text: a

text: phase

text: of

text: molecule

text: formation

text: on

text: cold

text: grain

text: surfaces

text: at

text: which

text: the

text: accreting

text: gas

text: is

text: atomic

text: H-

text: and

text: O-rich.

text: This

text: is

text: a

text: phase

text: of

text: relatively

text: low

text: densities

text: (n

text: cm

text: early

text: in

text: the

text: cloud

text: evolution

text: (H/H

text: ratios

text: decrease

text: rapidly

text: with

text: density;

text: Hollenbach

text: et

text: al.

text: The

text: ice

text: formation

text: threshold

text: of

text: A

text: mag

text: near

text: local

text: cloud

text: edges

text: is

text: V

text: understood

text: as

text: the

text: onset

text: of

text: rapid

text: ice

text: mantle

text: growth

text: after

text: a

text: monolayer

text: has

text: formed

text: and

text: the

text: eﬀect

text: of

text: photodesorption

text: decreases

text: with

text: increasing

text: extinction

text: by

text: dust

text: into

text: the

text: cloud

text: (A

text: ln(G

text: /n);

text: Hollenbach

text: et

text: al.

text: This

text: phase

text: also

text: includes

text: the

text: V

text: formation

text: of

text: CH

text: CO

text: (polar

text: component,

text: likely

text: via

text: CO+OH;

text: Ioppolo

text: et

text: al.

text: and

text: NH

text: which

text: are

text: all

text: intimately

text: mixed

text: with

text: H

text: O.

text: Variations

text: in

text: CO

text: /H

text: O

text: ratios

text: in

text: this

text: early

text: phase

text: reﬂect

text: variations

text: of

text: the

text: CO

text: accretion

text: rates.

text: On

text: one

text: hand,

text: if

text: the

text: gas

text: phase

text: formation

text: of

text: CO

text: is

text: incomplete,

text: e.g.,

text: at

text: low

text: extinctions,

text: more

text: O

text: can

text: be

text: included

text: in

text: H

text: O

text: (Whittet

text: et

text: al.,

text: O¨

text: berg

text: et

text: al.,

text: It

text: may

text: explain

text: the

text: possibly

text: CO

text: free

text: region

text: in

text: the

text: SMC

text: (Oliveira

text: et

text: al.,

text: and

text: CH

text: -rich

text: region

text: in

text: Galactic

text: cloud

text: edges

text: (O¨

text: berg

text: et

text: al.,

text: On

text: the

text: other

text: hand,

text: CO

text: accretion

text: rates

text: increase

text: at

text: lower

text: temperatures

text: and

text: at

text: higher

text: densities,

text: leading

text: to

text: enhanced

text: formation

text: of

text: CO

text: (up

text: to

text: a

text: factor

text: of

text: still

text: well

text: mixed

text: with

text: the

text: co-formed

text: H

text: O

text: species.

text: This

text: phase

text: is

text: CH

text: OH-poor

text: and

text: has

text: a

text: relatively

text: low

text: CO

text: freeze

text: out

text: At

text: the

text: same

text: time,

text: the

text: presence

text: of

text: the

text: µm

text: feature

text: and

text: some

text: absorption

text: underlying

text: the

text: µm

text: band

text: (Fig.

text: show

text: that

text: these

text: early

text: ices

text: are

text: already

text: quite

text: complex.

text: They

text: are

text: formed

text: on

text: a

text: short

text: time

text: scale

text: yr

text: at

text: n

text: cm

text: e.g.,

text: Hollenbach

text: et

text: al.

text: compared

text: to

text: the

text: cloud

text: life

text: time

text: yr)

text: and

text: compared

text: to

text: the

text: formation

text: time

text: of

text: new

text: species

text: by

text: interstellar

text: CRs

text: or

text: CR-induced

text: UV

text: ﬁelds


text: ta sessecorp lacimehc dna lacisyhp eht gnithgilhgih ,seltnam niarg yci fo noitisopmoc deniartsnoc yllanoitavresbo eht fo weiv citamehcS :01 erugiF sksid dna sepolevne OSY dna )3-1 sesahp( sduolc tnecseiuq ni sesahp yranoitulove evissergorp tneserper dluoc hcihw ,nwohs era sesahp xiS .yalp yradnoces dna RC ecneirepxe seci eht ,5-1 sesahp nI .der ni detacidni era snoitcaer ecafrus niarg ni gnitapicitrap seiceps esahp saG .)6-3 sesahp( gnivlovni snoitcaer ro snoitcaer lamreht ,)5 dna 4 sesahp( sesir erutarepmet eci eht sA .seiceps eci niam eht tceﬀa yllaminim ylno taht sdleﬁ VU mumixam( citsilaer era segats 5 tsrﬁ eht ni sezis eltnam dna niarg evitaler ehT .deniartsnoc yllanoitavresbo tsael si 6 egatS .deecorp yam slacidar .setarelecca noitalugaoc niarg ,)1 esahp( demrof era sreyal eci laitini eht retfA .)˚A 02 fo sezis eroc niarg laminim dna ˚A 05 fo ssenkciht eltnam 38 Boogert, Gerakines, & Whittet

text: ta

label: caption

text: sessecorp

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text: deniartsnoc

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text: eht

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text: erugiF

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text: dna

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text: sesahp(

text: sduolc

text: tnecseiuq

text: ni

text: sesahp

text: yranoitulove

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text: tneserper

text: dluoc

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text: ,nwohs

text: era

text: sesahp

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text: yradnoces

text: dna

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text: ni

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text: niarg

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text: gnivlovni

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text: eci

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text: segats

text: tsrﬁ

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text: dna

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text: ehT

text: .deniartsnoc

text: yllanoitavresbo

text: tsael

text: si

text: egatS

text: .deecorp

text: yam

text: slacidar

text: .setarelecca

text: noitalugaoc

text: niarg

text: esahp(

text: demrof

text: era

text: sreyal

text: eci

text: laitini

text: eht

text: retfA

text: .)˚A

text: fo

text: sezis

text: eroc

text: niarg

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text: dna

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text: fo

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text: eltnam

text: Boogert,

text: Gerakines,

text: Whittet


text: Observations of the Icy Universe; ARAA 53 (2015; accepted), v. 05/05/2015 47 Hagen W, Tielens AGGM, Greenberg JM. 1983. A&A 117:132 Hardegree-Ullman EE, Gudipati MS, Boogert ACA, et al. 2014. ApJ 784:172 Harker D, Bregman J, Tielens AGGM, Temi P, Rank D. 1997. A&A 324:629 Herbst E, van Dishoeck EF. 2009. ARAA, 47:427 Holbrook JC, Temi P. 1998. ApJ 496:280 Hollenbach DJ, Werner MW, Salpeter EE. 1971. ApJ 163:165 Hollenbach D, Kaufman MJ, Bergin EA, Melnick GJ. 2009. ApJ 690:1497 Honda M, Inoue AK, Fukagawa M, et al. 2009. ApJL 690:L110 Hough JH, Chrysostomou A, Messinger DW, et al. 1996. ApJ 461:902 Hudgins DM, Sandford SA, Allamandola LJ, Tielens AGGM. 1993. ApJS 86:713 Imanishi M, Maloney PR. 2003. ApJ 588:165 Imanishi M, Dudley CC, Maloney PR. 2006. ApJ 637:114 Ioppolo S, van Boheemen Y, Cuppen HM, van Dishoeck EF, Linnartz H. 2011. MNRAS, 413:2281 Ioppolo S, Sangiorgio I, Baratta GA, Palumbo ME. 2013. A&A 554:34 Ioppolo S, McGuire BA, Allodi MA, Blake GA. 2014. Faraday Discuss. 168:461 Jenkins EB. 2009. ApJ 700:1299 Jenniskens P. 1993. A&A 274:653 Keane JV, Boogert ACA, Tielens AGGM, Ehrenfreund P, Schutte WA. 2001a. A&A 375:L43 Keane JV, Tielens AGGM, Boogert ACA, Schutte WA, Whittet DCB. 2001b. A&A 376:254 Kerr TH, Adamson AJ, Whittet DCB. 1993. MNRAS 262:1047 Kim HJ, Evans NJ II, Dunham MM, Lee J-E, Pontoppidan KM. 2012. ApJ 758:38 Knacke RF, Cudaback DD, Gaustad JE. 1969. ApJ 158:151 Knacke RF, McCorkle S, Puetter RC, Erickson EF, Kraetschmer W. 1982. ApJ 260:141 Knacke RF, McCorkle SM. 1987. AJ 94:972 Knez C, Boogert ACA, Pontoppidan KM, et al. 2005. ApJL 635:L145 Lacy JH, Baas F, Allamandola LJ, et al. 1984. ApJ 276:533 Lacy JH, Carr JS, Evans NJ II, et al. 1991. ApJ 376:556 Lacy JH, Faraji H, Sandford SA, Allamandola LJ. 1998. ApJL 501:L105 Li Q, Liang SL, Li A. 2014. MNRAS 440:L56 Lindblad B. 1935. Nature 135:133 Linnartz H, Bossa JB, Bouwman J, et al. 2011. The Molecular Universe, IAU Symp 280, ed. J Cernicharo, R Bachiller, p. 390. Cambridge, UK: Cambridge Univ. Press Malfait K, Waelkens C, Waters LBFM, et al. 1998. A&A 332:L25

text: Observations

text: of

text: the

text: Icy

text: Universe;

text: ARAA

text: accepted),

text: v.

text: Hagen

text: W,

text: Tielens

text: AGGM,

text: Greenberg

text: JM.

text: A&A

text: Hardegree-Ullman

text: EE,

text: Gudipati

text: MS,

text: Boogert

text: ACA,

text: et

text: al.

text: ApJ

text: Harker

text: D,

text: Bregman

text: J,

text: Tielens

text: AGGM,

text: Temi

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text: Rank

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text: A&A

text: Herbst

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text: van

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text: EF.

text: ARAA,

text: Holbrook

text: JC,

text: Temi

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text: ApJ

text: Hollenbach

text: DJ,

text: Werner

text: MW,

text: Salpeter

text: EE.

text: ApJ

text: Hollenbach

text: D,

text: Kaufman

text: MJ,

text: Bergin

text: EA,

text: Melnick

text: GJ.

text: ApJ

text: Honda

text: M,

text: Inoue

text: AK,

text: Fukagawa

text: M,

text: et

text: al.

text: ApJL

text: Hough

text: JH,

text: Chrysostomou

text: A,

text: Messinger

text: DW,

text: et

text: al.

text: ApJ

text: Hudgins

text: DM,

text: Sandford

text: SA,

text: Allamandola

text: LJ,

text: Tielens

text: AGGM.

text: ApJS

text: Imanishi

text: M,

text: Maloney

text: PR.

text: ApJ

text: Imanishi

text: M,

text: Dudley

text: CC,

text: Maloney

text: PR.

text: ApJ

text: Ioppolo

text: S,

text: van

text: Boheemen

text: Y,

text: Cuppen

text: HM,

text: van

text: Dishoeck

text: EF,

text: Linnartz

text: H.

text: MNRAS,

text: Ioppolo

text: S,

text: Sangiorgio

text: I,

text: Baratta

text: GA,

text: Palumbo

text: ME.

text: A&A

text: Ioppolo

text: S,

text: McGuire

text: BA,

text: Allodi

text: MA,

text: Blake

text: GA.

text: Faraday

text: Discuss.

text: Jenkins

text: EB.

text: ApJ

text: Jenniskens

text: P.

text: A&A

text: Keane

text: JV,

text: Boogert

text: ACA,

text: Tielens

text: AGGM,

text: Ehrenfreund

text: P,

text: Schutte

text: WA.

text: A&A

text: Keane

text: JV,

text: Tielens

text: AGGM,

text: Boogert

text: ACA,

text: Schutte

text: WA,

text: Whittet

text: DCB.

text: A&A

text: Kerr

text: TH,

text: Adamson

text: AJ,

text: Whittet

text: DCB.

text: MNRAS

text: Kim

text: HJ,

text: Evans

text: NJ

text: II,

text: Dunham

text: MM,

text: Lee

text: J-E,

text: Pontoppidan

text: KM.

text: ApJ

text: Knacke

text: RF,

text: Cudaback

text: DD,

text: Gaustad

text: JE.

text: ApJ

text: Knacke

text: RF,

text: McCorkle

text: S,

text: Puetter

text: RC,

text: Erickson

text: EF,

text: Kraetschmer

text: W.

text: ApJ

text: Knacke

text: RF,

text: McCorkle

text: SM.

text: AJ

text: Knez

text: C,

text: Boogert

text: ACA,

text: Pontoppidan

text: KM,

text: et

text: al.

text: ApJL

text: Lacy

text: JH,

text: Baas

text: F,

text: Allamandola

text: LJ,

text: et

text: al.

text: ApJ

text: Lacy

text: JH,

text: Carr

text: JS,

text: Evans

text: NJ

text: II,

text: et

text: al.

text: ApJ

text: Lacy

text: JH,

text: Faraji

text: H,

text: Sandford

text: SA,

text: Allamandola

text: LJ.

text: ApJL

text: Li

text: Q,

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text: SL,

text: Li

text: A.

text: MNRAS

text: Lindblad

text: B.

text: Nature

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text: H,

text: Bossa

text: JB,

text: Bouwman

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text: et

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text: IAU

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text: ed.

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text: Cernicharo,

text: R

text: Bachiller,

text: p.

text: Cambridge,

text: UK:

text: Cambridge

text: Univ.

text: Press

text: Malfait

text: K,

text: Waelkens

text: C,

text: Waters

text: LBFM,

text: et

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text: A&A


text: aecnerefeR noitacﬁitnedI MHWF ν λ retnec retnec − − 1 mc 1 mc mµ 02 )stnenopmoc elpitlum( dneb OC 82-61 266-356 3.51-1.51 2 42 1 <O H/ OC ,ralop — 22 356 13.51— ∼ 2 2 42 1 OC/ OC ,ralopa — 11 2.266 01.51— 2 42 1 <<OC/ OC ,etulid — 5.2 0.066 51.51— 2 42 OC erup — 91 166+3.556 62.51+11.51— 2 42 1 >> OC/HO HC ,redluohs — 01 846 4.51— 2 3 ∼ 34 ,24 ,14 )suohproma( ecittal O H 001 722 44 2 ∼ 34 ,24 ,14 )enillatsyrc( ecittal O H 05 722 44 2 ∼ 34 ,24 ,14 )enillatsyrc( ecittal O H 05 161 26 2 nabaT :1 :noitaziretcarahc elﬁorp ro noitacﬁitnedi sti ot ylgnorts gnitubirtnoc noitacilbup a ot ecnerefer a te ekcanK :5 ,1002 truocedneH’d & siotraD :4 ,0002 .la te raihC :3 ,a1002 .la te enaeK :2 ,3002 .la te ,6791 .la te llirreM :9 ,9891 .la te htimS :8 ,3791 tserroF & ttelliG :7 ,0991 .la te noteldneP :6 ,2891 .la & ettuhcS :31 ,4102 .la te namllU-eergedraH :21 ,4991 .la te nerglleS :11 ,7891 elkroCcM & ekcanK :01 mirG :71 ,2002 .la te siotraD :61 ,2991 .la te alodnamallA :51 ,a4002 .la te tregooB :41 ,3002 annahK .la te tregooB :12 ,9991 .la te senikareG :02 ,2102 .la te awakiA :91 ,5891 .la te ellabeG :81 ,1991 .la te neziuhkeorB nav :52 ,3002 .la te nadippotnoP :42 ,4891 .la te ycaL :32 ,b0002 .la te tregooB :22 ,a0002 te obmulaP :92 ,a2002 .la te tregooB :82 ,1102 .la te neppuC :72 ,9791 .la te refioS :62 ,5002 .la te tettihW & bbiG :33 ,8002 .la te tregooB :23 ,6991 .la te ettuhcS :13 ,b1002 .la te enaeK :03 ,7991 .la :83 ,6991 .la te tregooB :73 ,1991 .la te ycaL :63 ,7991 .la te tregooB :53 ,9991 .la te ettuhcS :43 ,2002 ,9991 .la te tiaflaM :24 ,0991 .la te tnomO :14 ,9891 xoC :04 ,8991 .la te ycaL :93 ,2991 .la te rennikS b2002 .la te tregooB :44 ,8991 .la te siotraD :34 seiceps rehto dna HOOCH spahrep dna HO HC ni edom hcterts H-O eht morf snoitubirtnoC b 3 .serutaef etarapes sa detceted ton era tub ,detcepxe era .noitceted evitatneT c Observations of the Icy Universe; ARAA 53 (2015; accepted), v. 05/05/2015 9 ##LTLine## ##LTLine## ##LTLine## ##LTLine##

text: aecnerefeR

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text: mc

text: mc

text: mµ

text: )stnenopmoc

text: elpitlum(

text: dneb

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text: <O

text: H/

text: OC

text: ,ralop

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text: ##LTLine##

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