- ID:
- ivo://CDS.VizieR/J/ApJ/900/104
- Title:
- IR high-res. sp. of hot cores of AFGL2591 & AFGL2136
- Short Name:
- J/ApJ/900/104
- Date:
- 21 Mar 2022 09:36:08
- Publisher:
- CDS
- Description:
- We have performed a high-resolution 4-13{mu}m spectral survey of the hot molecular gas associated with the massive protostars AFGL 2591 and AFGL 2136, utilizing the Echelon Cross Echelle Spectrograph (EXES) on board the Stratospheric Observatory for Infrared Astronomy, and the iSHELL instrument and Texas EchelonCross Echelle Spectrograph (TEXES) on the NASA Infrared Telescope Facility (IRTF). Here we present the results of this survey with analysis of CO, HCN, C2H2, NH3, and CS, deriving the physical conditions for each species. Also from the IRTF, iSHELL data at 3{mu}m for AFGL 2591 are presented that show HCN and C2H2 in emission. In the EXES and TEXES data, all species are detected in absorption, and temperatures and abundances are found to be high (600K and 10^-6^, respectively). Differences of up to an order of magnitude in the abundances of transitions that trace the same ground-state level are measured for HCN and C2H2. The mid-infrared continuum is known to originate in a disk, hence we attribute the infrared absorption to arise in the photosphere of the disk. As absorption lines require an outwardly decreasing temperature gradient, we conclude that the disk is heated in the midplane by viscous heating due to accretion. We attribute the near-IR emission lines to scattering by molecules in the upper layers of the disk photosphere. The absorption lines trace the disk properties at 50 au where high-temperature gas-phase chemistry is taking place. Abundances are consistent with chemical models of the inner disk of Herbig disks.
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- ID:
- ivo://CDS.VizieR/J/A+A/318/879
- Title:
- IR photometry of L1551/IRS5
- Short Name:
- J/A+A/318/879
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe a new approach to the solution of the frequency-dependent stationary radiative transfer equation for axially-symmetric circumstellar dust disks. The method is applied to flared disks which are considered here as spheres with the polar cones removed. We have simplified the problem by computing the moments of the specific intensity only for the midplane and the surface of the flared disk. At the same time, we solve the radiative transfer equation exactly for an "equivalent" spherical envelope. The basic assumption is that density distribution in the disk depends only on the radial distance from the central star. This results in significantly faster calculations, reduces necessary computer memory, and allows incorporation of the algorithm into a hydrodynamical code. We applied our fast 2D radiative transfer code to a detailed modeling of the deeply embedded young stellar object (YSO) L1551 IRS 5. This is a YSO in the Taurus-Aurigae star-forming region, which has been very well studied with good spatial resolution and photometric data over the wide range from ultraviolet to millimeter wavelengths. Exploring the parameter space of our axially-symmetric models, we have found a self-consistent solution for L1551 IRS 5 explaining all available infrared and submm/mm continuum observations. Here, Appendices A, B, and C are presented, which are not available in the journal version of the paper. In Appendices A and B, one can find more details on the method and the overall iterative numerical scheme. Appendix C (Table C1) lists all published photometric observations of L1551 IRS 5, which we have found in the literature and which have been used in our modeling.
- ID:
- ivo://CDS.VizieR/J/ApJS/86/713
- Title:
- IR spectroscopy of ices
- Short Name:
- J/ApJS/86/713
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Laboratory spectra through the mid-infrared (4000 to 500cm^-1^ [2.5-20 micron]) have been used to calculate the optical constants (n and k) and integrated absorption coefficients (A) for a variety of pure and mixed molecular ices of relevance to astrophysics. The ices studied were H2O, CH3OH, CO2, OCS, CH4, CO2+CH4, CO2+OCS, CO+CH4, CO+OCS, O2+CH4, O2+OCS, N2+CH4, N2+OCS, H2O+CH4, H2O+OCS, and H2O+CH3OH+CO+NH3. In addition, the measurements have been extended through the far-infrared (500 to 50cm^1^ [20-200 micron]) for the H2O, CH3OH, and H2O+CH3OH+NH3 ices.
- ID:
- ivo://CDS.VizieR/J/ApJ/729/94
- Title:
- IR spectroscopy of PAH in 6-15{mu}m band
- Short Name:
- J/ApJ/729/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Polycyclic aromatic hydrocarbon (PAH) growth and destruction are thought to proceed via the occasional incorporation of five- and seven-membered fused ring defects in the hexagonal carbon skeleton. Using density functional theory, this paper investigates the effect such five- and seven-membered fused ring defects have on the infrared spectra of ovalene (OV; C_32_H_14_), circumovalene (c-OV; C_66_H_20_), and circumcircumovalene (cc-OV; C_112_H_26_). The defects make only small changes to the overall infrared (IR) spectra, both in the mid-IR and in the far-IR, of these species. In addition to small shifts in the positions of the bands between the PAHs with and without defects, the most common effect of the defects is to increase the number of bands. Except for an anion with the Stone-Wales defect, all of the species studied have the C-C stretching band at 6.3um or at longer wavelengths, the position in Classes B and C astronomical PAH spectra. In the case of the Stone-Wales anion, the band falls at 6.20um, suggesting that further study of defects is probably worthwhile, as some PAHs with defects might be important in those sources (Class A) that show a C-C stretching band that falls near 6.2um.
- ID:
- ivo://CDS.VizieR/J/ApJ/670/1115
- Title:
- IRS spectra at 38 positions in Galactic center
- Short Name:
- J/ApJ/670/1115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer IRS spectra (R~600, 10-38um) of 38 positions in the Galactic center, all at the same Galactic longitude and spanning +/-0.3{deg} in latitude. Our positions include the Arches Cluster, the Arched Filaments, regions near the Quintuplet Cluster, the "Bubble" lying along the same line of sight as the molecular cloud G0.11-0.11, and the diffuse interstellar gas along the line of sight at higher Galactic latitudes.
- ID:
- ivo://CDS.VizieR/J/A+A/392/239
- Title:
- IR survey of outflows in Orion A
- Short Name:
- J/A+A/392/239
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made an unbiased imaging survey of a 1.2 square degree area in the Orion A giant molecular cloud searching for molecular hydrogen emission line features seen in the v=1-0 S(1) line at a wavelength of 2.12{mu}m originating in shocks in outflows from young stellar objects. This survey provides for the first time an unbiased census of outflows over a significant portion of a giant molecular cloud, and yields a sample of outflows free from selection effects and with all objects located at roughly the same, well-known distance. In this paper, we present the data gathered in the course of the survey, provide a comprehensive list of all molecular hydrogen emission features found, and give a list of the 76 candidate outflows identified in the data set.
- ID:
- ivo://CDS.VizieR/J/ApJ/606/929
- Title:
- IR to mm observations of IRAS 18317-0757
- Short Name:
- J/ApJ/606/929
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution, multiwavelength-continuum, and molecular-line images of the massive star forming region IRAS 18317-0757. The global infrared through millimeter spectral energy distribution can be approximated by a two-temperature model (25 and 63K) with a total luminosity of approximately log(L/L_{sun}_)=5.2. Previous submillimeter imaging resolved this region into a cluster of five dust cores, one of which is associated with the ultracompact HII region G23.955+0.150, and another with a water maser. In our new 2.7mm continuum image obtained with BIMA, only the UCHII region is detected, with total flux and morphology in good agreement with the free-free emission in the VLA centimeter-wave maps. For the other four objects, the nondetections at 2.7mm and in the MSX mid-infrared bands are consistent with cool dust emission with a temperature of 13-40K and a luminosity of 1000-40000L_{sun}_. By combining single-dish and interferometric data, we have identified over two dozen virialized C^18^O cores in this region that contain ~40% of the total molecular gas mass present.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A61
- Title:
- Isolated starless cores dust temperature
- Short Name:
- J/A+A/592/A61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Constraining the temperature and density structure of dense molecular cloud cores is fundamental for understanding the initial conditions of star formation. We use Herschel observations of the thermal FIR dust emission from nearby isolated molecular cloud cores and combine them with ground-based submillimeter continuum data to derive observational constraints on their temperature and density structure. The aim of this study is to verify the validity of a ray-tracing inversion technique developed to derive the dust temperature and density structure of isolated starless cores directly from the dust emission maps and to test if the resulting temperature and density profiles are consistent with physical models. Using this ray-tracing inversion technique, we derive the dust temperature and density structure of six isolated starless cloud cores. We employ self-consistent radiative transfer modeling to the derived density profiles, treating the ISRF as the only heating source. The best-fit values of local strength of the ISRF and the extinction by the outer envelope are derived by comparing the self-consistently calculated temperature profiles with those derived by the ray-tracing method. We find that all starless cores are significantly colder inside than outside, with the core temperatures showing a strong negative correlation with peak column density. This suggests that their thermal structure is dominated by external heating from the ISRF and shielding by dusty envelopes. The temperature profiles derived with the ray-tracing inversion method can be well-reproduced with self-consistent radiative transfer models.
- ID:
- ivo://CDS.VizieR/J/A+A/474/883
- Title:
- ISOSS J23053+5953 maps
- Short Name:
- J/A+A/474/883
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Due to the short timescales involved and observational difficulties, our knowledge of the earliest phases of massive star formation remains incomplete. We aim to explore the physical conditions during the initial phases of high-mass star formation and to detect a genuine massive (mass M>8M_{sun}_) protostar at an early evolutionary stage.
- ID:
- ivo://CDS.VizieR/J/A+A/621/A143
- Title:
- Isotopic H_2_CS laboratory spectroscopic study
- Short Name:
- J/A+A/621/A143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Thioformaldehyde is an abundant molecule in various regions of the interstellar medium. However, available laboratory data limit the accuracies of calculated transition frequencies in the submillimeter region, in particular for minor isotopic species. We aim to determine spectroscopic parameters of isotopologs of H_2_CS that are accurate enough for predictions well into the submillimeter region.
