The c2d Spitzer spectroscopic survey of ices around low-mass young stellar objects. I. H2O and the 5-8 mu m bands

A.C.A. Boogert, K.M. Pontoppidan, C. Knez, F. Lahuis, J. Kessler-Silacci, E.F. van Dishoeck, G.A. Blake, J.C. Augereau, H.J. Fraser

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Abstract

To study the physical and chemical evolution of ices in solar-mass systems, a spectral survey is conducted of a sample of 41 low-luminosity YSOs (L ~ 0.1-10 L) using 3-38 μm Spitzer and ground-based spectra. The sample is complemented with previously published Spitzer spectra of background stars and with ISO spectra of well-studied massive YSOs (L ~ 105 L). The long-known 6.0 and 6.85 μm bands are detected toward all sources, with the Class 0-type YSOs showing the deepest bands ever observed. The 6.0 μm band is often deeper than expected from the bending mode of pure solid H2O. The additional 5-7 μm absorption consists of five independent components, which, by comparison to laboratory studies, must be from at least eight different carriers. Much of this absorption is due to simple species likely formed by grain surface chemistry, at abundances of 1%-30% for CH3OH, 3%-8% for NH3, 1%-5% for HCOOH, ~6% for H2CO, and ~0.3% for HCOO− relative to solid H2O. The 6.85 μm band has one or two carriers, of which one may be less volatile than H2O. Its carrier(s) formed early in the molecular cloud evolution and do not survive in the diffuse ISM. If an NH4+-containing salt is the carrier, its abundance relative to solid H2O is ~7%, demonstrating the efficiency of low-temperature acid-base chemistry or cosmic-ray-induced reactions. Possible origins are discussed for enigmatic, very broad absorption between 5 and 8 μm. Finally, the same ices are observed toward massive and low-mass YSOs, indicating that processing by internal UV radiation fields is a minor factor in their early chemical evolution.
LanguageEnglish
Pages985-1004
Number of pages20
JournalAstrophysical Journal
Volume678
Issue number2
DOIs
Publication statusPublished - 10 May 2008

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ice
chemical evolution
chemistry
cosmic ray
relative abundance
molecular clouds
radiation distribution
salt
cosmic rays
acid
luminosity
salts
stars
acids
young
chemical
laboratory
comparison
radiation

Keywords

  • astrochemistry
  • infrared
  • stars
  • abundances
  • molecules
  • star formation
  • infrared spectrograph irs
  • iso-sws observations
  • mu-m spectrum
  • interstellar ice
  • space-telescope
  • embedded protostars
  • absorption features
  • solid methanol
  • micron spectra
  • grain mantles

Cite this

Boogert, A. C. A., Pontoppidan, K. M., Knez, C., Lahuis, F., Kessler-Silacci, J., van Dishoeck, E. F., ... Fraser, H. J. (2008). The c2d Spitzer spectroscopic survey of ices around low-mass young stellar objects. I. H2O and the 5-8 mu m bands. Astrophysical Journal, 678(2), 985-1004. https://doi.org/10.1086/533425
Boogert, A.C.A. ; Pontoppidan, K.M. ; Knez, C. ; Lahuis, F. ; Kessler-Silacci, J. ; van Dishoeck, E.F. ; Blake, G.A. ; Augereau, J.C. ; Fraser, H.J. / The c2d Spitzer spectroscopic survey of ices around low-mass young stellar objects. I. H2O and the 5-8 mu m bands. In: Astrophysical Journal. 2008 ; Vol. 678, No. 2. pp. 985-1004.
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abstract = "To study the physical and chemical evolution of ices in solar-mass systems, a spectral survey is conducted of a sample of 41 low-luminosity YSOs (L ~ 0.1-10 L) using 3-38 μm Spitzer and ground-based spectra. The sample is complemented with previously published Spitzer spectra of background stars and with ISO spectra of well-studied massive YSOs (L ~ 105 L). The long-known 6.0 and 6.85 μm bands are detected toward all sources, with the Class 0-type YSOs showing the deepest bands ever observed. The 6.0 μm band is often deeper than expected from the bending mode of pure solid H2O. The additional 5-7 μm absorption consists of five independent components, which, by comparison to laboratory studies, must be from at least eight different carriers. Much of this absorption is due to simple species likely formed by grain surface chemistry, at abundances of 1{\%}-30{\%} for CH3OH, 3{\%}-8{\%} for NH3, 1{\%}-5{\%} for HCOOH, ~6{\%} for H2CO, and ~0.3{\%} for HCOO− relative to solid H2O. The 6.85 μm band has one or two carriers, of which one may be less volatile than H2O. Its carrier(s) formed early in the molecular cloud evolution and do not survive in the diffuse ISM. If an NH4+-containing salt is the carrier, its abundance relative to solid H2O is ~7{\%}, demonstrating the efficiency of low-temperature acid-base chemistry or cosmic-ray-induced reactions. Possible origins are discussed for enigmatic, very broad absorption between 5 and 8 μm. Finally, the same ices are observed toward massive and low-mass YSOs, indicating that processing by internal UV radiation fields is a minor factor in their early chemical evolution.",
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Boogert, ACA, Pontoppidan, KM, Knez, C, Lahuis, F, Kessler-Silacci, J, van Dishoeck, EF, Blake, GA, Augereau, JC & Fraser, HJ 2008, 'The c2d Spitzer spectroscopic survey of ices around low-mass young stellar objects. I. H2O and the 5-8 mu m bands' Astrophysical Journal, vol. 678, no. 2, pp. 985-1004. https://doi.org/10.1086/533425

The c2d Spitzer spectroscopic survey of ices around low-mass young stellar objects. I. H2O and the 5-8 mu m bands. / Boogert, A.C.A.; Pontoppidan, K.M.; Knez, C.; Lahuis, F.; Kessler-Silacci, J.; van Dishoeck, E.F.; Blake, G.A.; Augereau, J.C.; Fraser, H.J.

In: Astrophysical Journal, Vol. 678, No. 2, 10.05.2008, p. 985-1004.

Research output: Contribution to journalArticle

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AU - Boogert, A.C.A.

AU - Pontoppidan, K.M.

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AU - Lahuis, F.

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AU - van Dishoeck, E.F.

AU - Blake, G.A.

AU - Augereau, J.C.

AU - Fraser, H.J.

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N2 - To study the physical and chemical evolution of ices in solar-mass systems, a spectral survey is conducted of a sample of 41 low-luminosity YSOs (L ~ 0.1-10 L) using 3-38 μm Spitzer and ground-based spectra. The sample is complemented with previously published Spitzer spectra of background stars and with ISO spectra of well-studied massive YSOs (L ~ 105 L). The long-known 6.0 and 6.85 μm bands are detected toward all sources, with the Class 0-type YSOs showing the deepest bands ever observed. The 6.0 μm band is often deeper than expected from the bending mode of pure solid H2O. The additional 5-7 μm absorption consists of five independent components, which, by comparison to laboratory studies, must be from at least eight different carriers. Much of this absorption is due to simple species likely formed by grain surface chemistry, at abundances of 1%-30% for CH3OH, 3%-8% for NH3, 1%-5% for HCOOH, ~6% for H2CO, and ~0.3% for HCOO− relative to solid H2O. The 6.85 μm band has one or two carriers, of which one may be less volatile than H2O. Its carrier(s) formed early in the molecular cloud evolution and do not survive in the diffuse ISM. If an NH4+-containing salt is the carrier, its abundance relative to solid H2O is ~7%, demonstrating the efficiency of low-temperature acid-base chemistry or cosmic-ray-induced reactions. Possible origins are discussed for enigmatic, very broad absorption between 5 and 8 μm. Finally, the same ices are observed toward massive and low-mass YSOs, indicating that processing by internal UV radiation fields is a minor factor in their early chemical evolution.

AB - To study the physical and chemical evolution of ices in solar-mass systems, a spectral survey is conducted of a sample of 41 low-luminosity YSOs (L ~ 0.1-10 L) using 3-38 μm Spitzer and ground-based spectra. The sample is complemented with previously published Spitzer spectra of background stars and with ISO spectra of well-studied massive YSOs (L ~ 105 L). The long-known 6.0 and 6.85 μm bands are detected toward all sources, with the Class 0-type YSOs showing the deepest bands ever observed. The 6.0 μm band is often deeper than expected from the bending mode of pure solid H2O. The additional 5-7 μm absorption consists of five independent components, which, by comparison to laboratory studies, must be from at least eight different carriers. Much of this absorption is due to simple species likely formed by grain surface chemistry, at abundances of 1%-30% for CH3OH, 3%-8% for NH3, 1%-5% for HCOOH, ~6% for H2CO, and ~0.3% for HCOO− relative to solid H2O. The 6.85 μm band has one or two carriers, of which one may be less volatile than H2O. Its carrier(s) formed early in the molecular cloud evolution and do not survive in the diffuse ISM. If an NH4+-containing salt is the carrier, its abundance relative to solid H2O is ~7%, demonstrating the efficiency of low-temperature acid-base chemistry or cosmic-ray-induced reactions. Possible origins are discussed for enigmatic, very broad absorption between 5 and 8 μm. Finally, the same ices are observed toward massive and low-mass YSOs, indicating that processing by internal UV radiation fields is a minor factor in their early chemical evolution.

KW - astrochemistry

KW - infrared

KW - stars

KW - abundances

KW - molecules

KW - star formation

KW - infrared spectrograph irs

KW - iso-sws observations

KW - mu-m spectrum

KW - interstellar ice

KW - space-telescope

KW - embedded protostars

KW - absorption features

KW - solid methanol

KW - micron spectra

KW - grain mantles

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DO - 10.1086/533425

M3 - Article

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EP - 1004

JO - Astrophysical Journal

T2 - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2

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Boogert ACA, Pontoppidan KM, Knez C, Lahuis F, Kessler-Silacci J, van Dishoeck EF et al. The c2d Spitzer spectroscopic survey of ices around low-mass young stellar objects. I. H2O and the 5-8 mu m bands. Astrophysical Journal. 2008 May 10;678(2):985-1004. https://doi.org/10.1086/533425