Processing of Icy Mantles in Protostellar Envelopes

We have obtained CO absorption profiles of several young stellar objects (YSOs), spanning a range of mass and luminosity, in order to investigate their ice mantle composition. We present the first detection of CO toward the class I YSO L1489 IRS in the Taurus dark cloud. In general, the CO profiles for YSOs show evidence for both processed and pristine ices in the same line of sight; strong indirect evidence for CO2 is suggested in R CrA IRS 7, L1489 IRS, Elias 18, and GL 961E. Toward other sources (R CrA IRS 1, IRS 2, W33A, NGC 7538 IRS 9, Mon R2 IRS 2) CO is present in (nearly) pure form. We propose an evolutionary scenario to explain the chemical diversity of the icy mantles toward these objects.

[1]  S. Sandford,et al.  The 2140 cm−1 (4.673 microns) Solid CO Band: The Case for Interstellar O2 and N2 and the Photochemistry of Nonpolar Interstellar Ice Analogs , 1997, The Astrophysical journal.

[2]  A. Adamson,et al.  Three Micron Hydrocarbon and Methanol Absorption in Taurus , 1996 .

[3]  A. Lazarian,et al.  Interstellar Polarization from CO and XCN Mantled Grains: A Severe Test for Grain Alignment Mechanisms , 1996 .

[4]  P. Roche,et al.  Interstellar Dust Absorption Features in the Infrared Spectrum of HH 100-IR: Searching for the Nitrogen Component of the Ices , 1996 .

[5]  T. Kerr,et al.  High-Resolution Studies of Solid CO in the Taurus Dark Cloud: Characterizing the Ices in Quiescent Clouds , 1995 .

[6]  Scott A. Sandford,et al.  Organic Compounds Produced by Photolysis of Realistic Interstellar and Cometary Ice Analogs Containing Methanol , 1995 .

[7]  Y. Pendleton,et al.  Evidence for chemical processing of precometary icy grains in circumstellar environments of pre-main-sequence stars , 1995 .

[8]  T. Nagata,et al.  THE NATURE OF CO AND H2O ICES IN THE CORONA AUSTRALIS MOLECULAR CLOUD , 1994 .

[9]  T. Kerr,et al.  Solid Carbon Monoxide in the Serpens Dark Cloud (Grad. Stud. Prize) 30 Min , 1993 .

[10]  S. Sandford,et al.  Detection of the 2165 inverse centimeter (4.619 micron) XCN band in the spectrum of L1551 IRS 5. , 1993, The Astrophysical journal.

[11]  T. Kerr,et al.  Infrared spectroscopy of solid CO: the ρ Ophiuchi molecular cloud , 1993 .

[12]  J. Graham,et al.  Ice grains in the Corona Australis molecular cloud , 1993 .

[13]  A. Tielens,et al.  On the molecular complexity of the hot cores in Orion A - Grain surface chemistry as 'The last refuge of the scoundrel' , 1992 .

[14]  S. Sandford,et al.  Infrared spectroscopy of dense clouds in the C-H stretch region: methanol and "diamonds." , 1992, The Astrophysical journal.

[15]  M. Burton.  An Infrared Imaging Survey of the ρ Oph and R CrA Dark Cloud Cores , 1992, Publications of the Astronomical Society of Australia.

[16]  A. Tielens,et al.  Interstellar solid CO: polar and nonpolar interstellar ices. , 1991, The Astrophysical journal.

[17]  Wen-Ping Chen,et al.  Changing environments of pre-main-sequence stars and their effect on the 3 microns ice feature , 1991 .

[18]  Neal J. Evans,et al.  Discovery of interstellar methane - Observations of gaseous and solid CH4 absorption toward young stars in molecular clouds , 1991 .

[19]  M. Allen,et al.  Hot and cold gas toward young stellar objects , 1990 .

[20]  F. Ménard,et al.  Parameters of Disks around Young Stellar Objects from Polarization Observations , 1990 .

[21]  Three micron spectroscopy of low-mass pre-main-sequence stars , 1990 .

[22]  S. Sandford,et al.  The physical and infrared spectral properties of CO2 in astrophysical ice analogs. , 1990, The Astrophysical journal.

[23]  T. Nagata,et al.  Three Micron Ice-Band Features in the rho Ophiuchi Sources , 1990 .

[24]  W. Duley,et al.  Infrared spectroscopy of dust in the Taurus dark clouds: solid carbon monoxide , 1989 .

[25]  I. Cruz-Gonzalez,et al.  Radio continuum observations of IRAS sources associated with dense cores , 1989 .

[26]  K. Sellgren,et al.  Absorption features in the 3 micron spectra of protostars , 1989 .

[27]  M. Allen,et al.  The gas environment of the young stellar object GL 2591 studied by infrared spectroscopy , 1989 .

[28]  P. Ho,et al.  Ammonia observations of outflow regions , 1989 .

[29]  J. Greenberg,et al.  The temperature dependence of the CO infrared band strength in CO:H2O ices , 1989 .

[30]  Scott A. Sandford,et al.  Photochemical and thermal evolution of interstellar/precometary ice analogs , 1988 .

[31]  M. Allen,et al.  The ratio of solid to gas phase CO in the line of sight to W33A , 1988 .

[32]  P. Roche,et al.  Infrared spectroscopy of dust in the Taurus dark clouds: ice and silicates , 1988 .

[33]  S. Sandford,et al.  Laboratory studies of the infrared spectral properties of CO in astrophysical ices. , 1988, The Astrophysical journal.

[34]  Alexander Brown.  Radio emission from pre-main-sequence stars in Corona Australis , 1987 .

[35]  J. Greenberg,et al.  Ions in grain mantles - The 4.62 micron absorption by OCN(-) in W33A , 1987 .

[36]  G. Fuller,et al.  Near-infrared and optical observations of IRAS sources in and near dense cores , 1987 .

[37]  J. Storey,et al.  The nature of the infrared cluster in the R Coronae Australis cloud core. , 1986 .

[38]  U. Fink,et al.  Interstellar absorption features toward the compact infrared source W33A , 1985 .

[39]  A. Longmore,et al.  Solid CO in the Taurus dark clouds , 1985 .

[40]  D. Thompson,et al.  GL 961-W : a pre-main-sequence object. , 1985 .

[41]  J. Storey,et al.  The Coronet, an obscured cluster adjacent to R Corona Austrina , 1984 .

[42]  C. Lonsdale,et al.  4.6 Micron absorption features due to solid phase CO and Cyano group molecules toward compact infrared sources , 1984 .

[43]  M. Bode,et al.  Interstellar ice grains in the Taurus molecular clouds , 1983, Nature.

[44]  K. M. Merrill,et al.  Infrared spectra of protostars : composition of the dust shells. , 1982 .

[45]  H. Marraco,et al.  On the distance and membership of the R CrA T association. , 1981 .

[46]  J. C. Blades,et al.  Grain growth in interstellar clouds , 1980 .

[47]  I. Gatley,et al.  An infrared study of the NGC 7538 region , 1979 .

[48]  F. Gillett,et al.  Infrared observations of the OH source W33 A , 1978 .

[49]  J. Elias.  A study of the Taurus dark cloud complex , 1978 .

[50]  G. Neugebauer,et al.  Infrared observations of Monoceros R2 , 1976 .

[51]  S. Strom,et al.  An infrared source associated with a Herbig--Haro object , 1974 .