VLT-ISAAC 3-5 μm spectroscopy of embedded young low-mass stars. III. Intermediate-mass sources in vela

W.F. Thi, E.F. van Dishoeck, E. Dartois, K.M. Pontoppidan, W.A. Schutte, P. Ehrenfreund, L. d'Hendecourt, H.J. Fraser

Research output: Contribution to journalArticle

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Abstract

Aims. We study in this paper the ice composition in the envelope around intermediate-mass class I Young Stellar Objects (YSOs).
Methods. We performed a spectroscopic survey toward five intermediate-mass class I YSOs located in the Southern Vela molecular cloud in the L (2.85-4.0 m) and M (4.55-4.8 m) bands at resolving powers -800 up to 10 000, using the Infrared Spectrometer and Array Camera mounted on the Very Large Telescope-ANTU. Lower mass companion objects were observed simultaneously in both bands.
Results. Solid H 2O at 3 m is detected in all sources, including the companion objects. CO ice at 4.67 m is detected in a few main targets and one companion object. One object ( LLN 19 ) shows little CO ice but strong gas-phase CO ro-vibrational lines in absorption. The CO ice profiles are different from source to source. The amount of water ice and CO ice trapped in a water-rich mantle may correlate with the flux ratio at 12 and 25 m. The abundance of H2O-rich CO likely correlates with that of water ice. A weak feature at 3.54 m attributed to solid CH 3OH and a broad feature near 4.62 m are observed toward , but not toward the other sources. The derived abundances of solid CH 3OH and OCN- are ~% and ~% of the H 2O ice abundance respectively. The H 2O optical depths do not show an increase with envelope mass, nor do they show lower values for the companion objects compared with the main protostar. The line-of-sight CO ice abundance does not correlate with the source bolometric luminosity.
Conclusions. Comparison of the solid CO profile toward LLN 17 , which shows an extremely broad CO ice feature, and that of its lower mass companion at a few thousand AU, which exhibits a narrow profile, together with the detection of OCN- toward LLN 17 provide direct evidences for local thermal processing of the ice.
LanguageEnglish
Pages251-265
Number of pages14
JournalAstronomy and Astrophysics
Volume449
Issue number1
DOIs
Publication statusPublished - Apr 2006

Fingerprint

ice
spectroscopy
stars
young
envelopes
ice feature
profiles
methylidyne
water
protostars
infrared spectrometers
optical depth
molecular clouds
optical thickness
line of sight
spectrometer
Earth mantle
mantle
cameras
luminosity

Keywords

  • astrophysics
  • interstellar ice
  • stars
  • young stellar objects

Cite this

Thi, W. F., van Dishoeck, E. F., Dartois, E., Pontoppidan, K. M., Schutte, W. A., Ehrenfreund, P., ... Fraser, H. J. (2006). VLT-ISAAC 3-5 μm spectroscopy of embedded young low-mass stars. III. Intermediate-mass sources in vela. Astronomy and Astrophysics, 449(1), 251-265. https://doi.org/10.1051/0004-6361:20052931
Thi, W.F. ; van Dishoeck, E.F. ; Dartois, E. ; Pontoppidan, K.M. ; Schutte, W.A. ; Ehrenfreund, P. ; d'Hendecourt, L. ; Fraser, H.J. / VLT-ISAAC 3-5 μm spectroscopy of embedded young low-mass stars. III. Intermediate-mass sources in vela. In: Astronomy and Astrophysics. 2006 ; Vol. 449, No. 1. pp. 251-265.
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abstract = "Aims. We study in this paper the ice composition in the envelope around intermediate-mass class I Young Stellar Objects (YSOs).Methods. We performed a spectroscopic survey toward five intermediate-mass class I YSOs located in the Southern Vela molecular cloud in the L (2.85-4.0 m) and M (4.55-4.8 m) bands at resolving powers -800 up to 10 000, using the Infrared Spectrometer and Array Camera mounted on the Very Large Telescope-ANTU. Lower mass companion objects were observed simultaneously in both bands.Results. Solid H 2O at 3 m is detected in all sources, including the companion objects. CO ice at 4.67 m is detected in a few main targets and one companion object. One object ( LLN 19 ) shows little CO ice but strong gas-phase CO ro-vibrational lines in absorption. The CO ice profiles are different from source to source. The amount of water ice and CO ice trapped in a water-rich mantle may correlate with the flux ratio at 12 and 25 m. The abundance of H2O-rich CO likely correlates with that of water ice. A weak feature at 3.54 m attributed to solid CH 3OH and a broad feature near 4.62 m are observed toward , but not toward the other sources. The derived abundances of solid CH 3OH and OCN- are ~{\%} and ~{\%} of the H 2O ice abundance respectively. The H 2O optical depths do not show an increase with envelope mass, nor do they show lower values for the companion objects compared with the main protostar. The line-of-sight CO ice abundance does not correlate with the source bolometric luminosity. Conclusions. Comparison of the solid CO profile toward LLN 17 , which shows an extremely broad CO ice feature, and that of its lower mass companion at a few thousand AU, which exhibits a narrow profile, together with the detection of OCN- toward LLN 17 provide direct evidences for local thermal processing of the ice.",
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Thi, WF, van Dishoeck, EF, Dartois, E, Pontoppidan, KM, Schutte, WA, Ehrenfreund, P, d'Hendecourt, L & Fraser, HJ 2006, 'VLT-ISAAC 3-5 μm spectroscopy of embedded young low-mass stars. III. Intermediate-mass sources in vela' Astronomy and Astrophysics, vol. 449, no. 1, pp. 251-265. https://doi.org/10.1051/0004-6361:20052931

VLT-ISAAC 3-5 μm spectroscopy of embedded young low-mass stars. III. Intermediate-mass sources in vela. / Thi, W.F.; van Dishoeck, E.F.; Dartois, E.; Pontoppidan, K.M.; Schutte, W.A.; Ehrenfreund, P.; d'Hendecourt, L.; Fraser, H.J.

In: Astronomy and Astrophysics, Vol. 449, No. 1, 04.2006, p. 251-265.

Research output: Contribution to journalArticle

TY - JOUR

T1 - VLT-ISAAC 3-5 μm spectroscopy of embedded young low-mass stars. III. Intermediate-mass sources in vela

AU - Thi, W.F.

AU - van Dishoeck, E.F.

AU - Dartois, E.

AU - Pontoppidan, K.M.

AU - Schutte, W.A.

AU - Ehrenfreund, P.

AU - d'Hendecourt, L.

AU - Fraser, H.J.

PY - 2006/4

Y1 - 2006/4

N2 - Aims. We study in this paper the ice composition in the envelope around intermediate-mass class I Young Stellar Objects (YSOs).Methods. We performed a spectroscopic survey toward five intermediate-mass class I YSOs located in the Southern Vela molecular cloud in the L (2.85-4.0 m) and M (4.55-4.8 m) bands at resolving powers -800 up to 10 000, using the Infrared Spectrometer and Array Camera mounted on the Very Large Telescope-ANTU. Lower mass companion objects were observed simultaneously in both bands.Results. Solid H 2O at 3 m is detected in all sources, including the companion objects. CO ice at 4.67 m is detected in a few main targets and one companion object. One object ( LLN 19 ) shows little CO ice but strong gas-phase CO ro-vibrational lines in absorption. The CO ice profiles are different from source to source. The amount of water ice and CO ice trapped in a water-rich mantle may correlate with the flux ratio at 12 and 25 m. The abundance of H2O-rich CO likely correlates with that of water ice. A weak feature at 3.54 m attributed to solid CH 3OH and a broad feature near 4.62 m are observed toward , but not toward the other sources. The derived abundances of solid CH 3OH and OCN- are ~% and ~% of the H 2O ice abundance respectively. The H 2O optical depths do not show an increase with envelope mass, nor do they show lower values for the companion objects compared with the main protostar. The line-of-sight CO ice abundance does not correlate with the source bolometric luminosity. Conclusions. Comparison of the solid CO profile toward LLN 17 , which shows an extremely broad CO ice feature, and that of its lower mass companion at a few thousand AU, which exhibits a narrow profile, together with the detection of OCN- toward LLN 17 provide direct evidences for local thermal processing of the ice.

AB - Aims. We study in this paper the ice composition in the envelope around intermediate-mass class I Young Stellar Objects (YSOs).Methods. We performed a spectroscopic survey toward five intermediate-mass class I YSOs located in the Southern Vela molecular cloud in the L (2.85-4.0 m) and M (4.55-4.8 m) bands at resolving powers -800 up to 10 000, using the Infrared Spectrometer and Array Camera mounted on the Very Large Telescope-ANTU. Lower mass companion objects were observed simultaneously in both bands.Results. Solid H 2O at 3 m is detected in all sources, including the companion objects. CO ice at 4.67 m is detected in a few main targets and one companion object. One object ( LLN 19 ) shows little CO ice but strong gas-phase CO ro-vibrational lines in absorption. The CO ice profiles are different from source to source. The amount of water ice and CO ice trapped in a water-rich mantle may correlate with the flux ratio at 12 and 25 m. The abundance of H2O-rich CO likely correlates with that of water ice. A weak feature at 3.54 m attributed to solid CH 3OH and a broad feature near 4.62 m are observed toward , but not toward the other sources. The derived abundances of solid CH 3OH and OCN- are ~% and ~% of the H 2O ice abundance respectively. The H 2O optical depths do not show an increase with envelope mass, nor do they show lower values for the companion objects compared with the main protostar. The line-of-sight CO ice abundance does not correlate with the source bolometric luminosity. Conclusions. Comparison of the solid CO profile toward LLN 17 , which shows an extremely broad CO ice feature, and that of its lower mass companion at a few thousand AU, which exhibits a narrow profile, together with the detection of OCN- toward LLN 17 provide direct evidences for local thermal processing of the ice.

KW - astrophysics

KW - interstellar ice

KW - stars

KW - young stellar objects

U2 - 10.1051/0004-6361:20052931

DO - 10.1051/0004-6361:20052931

M3 - Article

VL - 449

SP - 251

EP - 265

JO - Astronomy and Astrophysics

T2 - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

IS - 1

ER -

Thi WF, van Dishoeck EF, Dartois E, Pontoppidan KM, Schutte WA, Ehrenfreund P et al. VLT-ISAAC 3-5 μm spectroscopy of embedded young low-mass stars. III. Intermediate-mass sources in vela. Astronomy and Astrophysics. 2006 Apr;449(1):251-265. https://doi.org/10.1051/0004-6361:20052931