- ID:
- ivo://CDS.VizieR/J/A+A/657/A99
- Title:
- The rotational spectrum of glycinamide
- Short Name:
- J/A+A/657/A99
- Date:
- 21 Mar 2022 09:35:44
- Publisher:
- CDS
- Description:
- Glycinamide (NH_2_CH_2_C(O)NH_2_) is considered to be one of the possible precursors of the simplest amino acid glycine. Its only rotational spectrum reported so far has been in the cm-wave region on a laser-ablation generated supersonic expansion sample. The aim of this work is to extend the laboratory spectrum of glycinamide into the millimetre wave region to support its searches in the interstellar medium and to perform the first check for its presence in the high-mass star forming region Sagittarius B2(N). Glycinamide was synthesised chemically and was studied with broadband rotational spectroscopy in the 90-329 GHz region with the sample in slow flow at 50{deg}C. Tunneling across a low energy barrier between two symmetry equivalent configurations of the molecule resulted in splitting of each vibrational state and many perturbations in associated rotational energy levels, requiring careful coupled state fits for each vibrational doublet. We searched for emission of glycinamide in the imaging spectral line survey ReMoCA performed with the Atacama Large Millimetre/submillimetre Array toward Sgr B2(N). The astronomical spectra were analysed under the assumption of local thermodynamic equilibrium. We report the first analysis of the mm-wave rotational spectrum of glycinamide, resulting in fitting to experimental measurement accuracy of over 1200 assigned and measured transition frequencies for the ground state tunneling doublet, of many lines for tunneling doublets for two singly excited vibrational states, and determination of precise vibrational separation in each doublet. We did not detect emission from glycinamide in the hot molecular core Sgr B2(N1S). We derived a column density upper limit of 1.5x10^16^cm^-2^, which implies that glycinamide is at least seven times less abundant than aminoacetonitrile and 1.8 times less abundant than urea in this source.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/646/A170
- Title:
- The Serpens filament 13CO, C18O and C17O datacubes
- Short Name:
- J/A+A/646/A170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Serpens filament, a prominent elongated structure in a relatively nearby molecular cloud, is believed to be at an early evolutionary stage, so studying its physical and chemical properties can shed light on filament formation and early evolution. The main goal is to address the physical and chemical properties as well as dynamical state of the Serpens filament at a spatial resolution of ~0.07pc and a spectral resolution of ~0.1~km/s. We performed ^13^CO (1-0), C^18^O (1-0), C^17^O (1-0), ^13^CO (2-1), C^18^O (2-1), and C^17^O (2-1) imaging observations toward the Serpens filament with the IRAM-3 m and APEX telescopes. Widespread narrow ^13^CO (2-1) self-absorption is observed in this filament, causing the ^13^CO morphology to be different from the filamentary structure traced by C^18^O and C^17^O. Our excitation analysis suggests that the opacities of C^18^O transitions become higher than unity in most regions, and this analysis confirms the presence of widespread CO depletion. Further we show that the local velocity gradients have a tendency to be perpendicular to the filament's long axis in the outskirts and parallel to the large-scale magnetic field direction. The magnitudes of the local velocity gradients decrease toward the filament's crest. The observed velocity structure can be a result of gravity-driven accretion flows. The isochronic evolutionary track of the C^18^O freeze-out process indicates the filament is young with an age of <~2Myr. We propose that the Serpens filament is a newly-formed slightly-supercritical structure which appears to be actively accreting material from its ambient gas.
- ID:
- ivo://CDS.VizieR/J/A+A/401/873
- Title:
- The SMC in the Far Infrared
- Short Name:
- J/A+A/401/873
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ISOPHOT experiment onboard the ISO satellite generated a complete view of the Small Magellanic Cloud (SMC) at 170{mu}m with 1.5arcmin resolution. The map is analysed using an automated photometry program enabling accurate photometric characterization of the far infrared (FIR) emitting regions. In this paper, the sources detected at 170{mu}m are compared with those obtainable from the IRAS satellite data. For this purpose, the 12{mu}m, 25{mu}m, 60{mu}m, and 100{mu}m IRAS high resolution (HiRes) maps of the SMC are re-examined using the same method. In contrast to former studies, this provides an all-band ISO/IRAS source catalog which is no longer based on eyeball classification, but relies on an algorithm which is capable of automated, repeatable photometry, even for irregular sources. In the mid infrared IRAS bands numerous bright FIR emitting regions in the SMC are detected and classified: 73 sources are found at 12{mu}m, 135 at 25{mu}m (most of them with F{nu}<1.0Jy). All three FIR bands at 170{mu}m, 100{mu}m, and 60{mu}m reproduce the overall morphological structure of the SMC similarly well, in contrast to the 12{mu}m and 25{mu}m maps which only contain a limited number of extended sources and do not trace the main body of the SMC. 243 sources are detected in the ISO 170{mu}m map, 155 of them with F{nu}>=2.0Jy. Comparable numbers are found for the two FIR IRAS maps at 60{mu}m (384) and 100{mu}m (338) with fluxes up to 450Jy. 70 of the 243 170{mu}m sources are assigned a general SED type (cold , warm , i.e., <30K, >30K) for the first time. A comparison with earlier IRAS results suggests that many source flux densities in those studies have been under- or overestimated because of non-standardized fitting methods. Many sources with flux densities up to 40Jy listed in former catalogs cannot be identified in our data.
- ID:
- ivo://CDS.VizieR/J/AJ/150/40
- Title:
- The Spitzer c2d survey of clouds. XII. Perseus
- Short Name:
- J/AJ/150/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Spitzer Space Telescope mapped the Perseus molecular cloud complex with the Infrared Array Camera (IRAC) and the Multi-Band Imaging Photometer for Spitzer (MIPS) as part of the c2d Spitzer Legacy project. This paper combines the observations from both instruments giving an overview of low-mass star formation across Perseus from 3.6 to 70{mu}m. We provide an updated list of young stellar objects (YSOs) with new classifications and source fluxes from previous works, identifying 369 YSOs in Perseus with the Spitzer data set. By synthesizing the IRAC and MIPS maps of Perseus and building on the work of previous papers in this series, we present a current census of star formation across the cloud and within smaller regions. Sixty-seven percent of the YSOs are associated with the young clusters NGC 1333 and IC 348. The majority of the star formation activity in Perseus occurs in the regions around the clusters to the eastern and western ends of the cloud complex. The middle of the cloud is nearly empty of YSOs despite containing regions of high visual extinction. The western half of Perseus contains three-quarters of the total number of embedded YSOs (Class 0+I and Flat spectral energy distribution sources) in the cloud and nearly as many embedded YSOs as Class II and III sources. Class II and III objects greatly outnumber Class 0+I objects in eastern Perseus and IC 348. These results are consistent with previous age estimates for the clusters. Across the cloud, 56% of YSOs and 91% of the Class 0+I and Flat sources are in areas where A_v_>=5mag, indicating a possible extinction threshold for star formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/741/79
- Title:
- The Spitzer-SDSS-GALEX Spectroscopic Survey
- Short Name:
- J/ApJ/741/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Spitzer-SDSS-GALEX Spectroscopic Survey (SSGSS) provides a new sample of 101 star-forming galaxies at z<0.2 with unprecedented multi-wavelength coverage. New mid- to far-infrared spectroscopy from the Spitzer Space Telescope is added to a rich suite of previous imaging and spectroscopy, including ROSAT, Galaxy Evolution Explorer, Sloan Digital Sky Survey, Two Micron All Sky Survey, and Spitzer/SWIRE. Sample selection ensures an even coverage of the full range of normal galaxy properties, spanning two orders of magnitude in stellar mass, color, and dust attenuation. In this paper we present the SSGSS data set, describe the science drivers, and detail the sample selection, observations, data reduction, and quality assessment.
- ID:
- ivo://CDS.VizieR/J/ApJ/723/845
- Title:
- The submillimeter spectrum of glycolaldehyde
- Short Name:
- J/ApJ/723/845
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Glycolaldehyde (HOCH_2_CHO) is a sugar-related interstellar prebiotic molecule that has been detected in two star-forming regions, Sgr B2(N) and G31.41+0.31. Glycolaldehyde is suspected to form from photodissociation-driven ice chemistry, and therefore can be used to trace complex organic chemistry in interstellar environments. The relative abundance of glycolaldehyde to its structural isomers, methyl formate (HCOOCH_3_) and acetic acid (CH_3_COOH), can be used to constrain astrochemical models. Given its central role in the complex chemistry of the interstellar medium, glycolaldehyde has been suggested as a prime molecular target for upcoming high-frequency molecular line searches using new far-infrared observatories. In particular, glycolaldehyde is a target for the Herschel Space Observatory HEXOS Key Program, which is conducting spectral line surveys of the Sgr B2(N) and Orion KL star-forming regions across the entire HIFI band. Laboratory investigation of glycolaldehyde in the HIFI frequency range is required before its lines can be identified in these spectra. We have therefore acquired the laboratory spectrum of glycolaldehyde in selected frequency ranges across the submillimeter range. We present here the laboratory spectral analysis of the ground vibrational state of glycolaldehyde up to 1.2THz.
- ID:
- ivo://CDS.VizieR/J/A+A/563/A137
- Title:
- THz spectrum of methylamine
- Short Name:
- J/A+A/563/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Methylamine (CH_3_NH_2_) is the simplest primary alkylamine and has been detected in the interstellar medium. The molecule is relatively light, with the 50K Boltzmann peak appearing near 800GHz. However, reliable predictions for its rotational spectrum are available only up to 500GHz. Spectroscopic analyses have been complicated by the two large amplitude motions: internal rotation of the methyl top and inversion of the amino group. The aims is to provide reliable predictions of the methylamine ground state rotational spectrum above 500GHz we studied its rotational spectrum in the frequency range from 500 to 2650GHz. The spectra of methylamine were recorded using the spectrometers based on Schottky diode frequency multiplication chains in the Lille laboratory (500-945GHz) and in JPL (1060-2660GHz). The analysis of the rotational spectrum of methylamine in the ground vibrational state was performed on the basis of the group-theoretical high barrier tunneling Hamiltonian developed for methylamine by Ohashi and Hougen. In the recorded spectra we have assigned 1849 new rotational transitions of methylamine. They were fitted together with previously published data to a Hamiltonian model that uses 76 parameters with overall weighted rms deviation of 0.87. On the basis of the new spectroscopic results, predictions of transition frequencies in the frequency range up to 3THz with J<50 and Ka<20 are presented.
- ID:
- ivo://CDS.VizieR/J/A+A/576/A39
- Title:
- THz spectrum of the monodeuterated methyl formate
- Short Name:
- J/A+A/576/A39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Laboratory spectral recordings and accurate molecular spectral analysis of any potential interstellar molecule are essential to generate a complete spectroscopic line list. This permits the prediction of the frequencies and intensities of any transition for its subsequent identification in the interstellar medium. Present analysis of DCOOCH_3_ is aimed to provide a comprehensive spectral catalog that encompasses as much as possible the frequency coverage of the new generation far-IR and submillimeter wave observation facilities. A new measurement of the rotational spectrum of DCOOCH_3_ has been carried out in the JPL laboratory in the frequency range from 0.85 to 1.5 THz. The new data were analyzed jointly with literature data using the Rho Axis Method (RAM), a tool developed for the spectral analysis of molecules with large amplitude internal CH_3_ rotors. Twenty seven spectroscopic constants of DCOOCH_3_ have been fitted to 3763 transitions with maximum values of J=69 and Ka=36 of the ground torsional state with a standard (unitless) deviation of 0.97. With respect to prior work, this is a significantly better result that was obtained with 2060 more transitions while also achieving a better accuracy for the new parameter values.
- ID:
- ivo://CDS.VizieR/J/MNRAS/404/1321
- Title:
- TiII in Milky way and Magellanic clouds
- Short Name:
- J/MNRAS/404/1321
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss several sets of TiII absorption-line data, which probe a variety of interstellar environments in our Galaxy and in the Magellanic Clouds. Comparisons of high-resolution [full width at half-maximum (FWHM)~1.3-1.5km/s] TiII spectra of Galactic targets with corresponding high-resolution spectra of NaI, KI and CaII reveal both similarities and differences in the detailed structure of the absorption-line profiles - reflecting component-to-component differences in the ionization and depletion behaviour of those species. Moderate-resolution (FWHM~3.4-4.5km/s) spectra of more heavily reddened Galactic stars provide more extensive information on the titanium depletion in colder, denser clouds - where more than 99.9 per cent of the Ti may be in the dust phase. Moderate-resolution (FWHM~4.5-8.7km/s) spectra of stars in the Magellanic Clouds suggest that the titanium depletion is generally much less severe in the Large and Small Magellanic Clouds than in our Galaxy [for a given N(Htot), E(B-V), or molecular fraction f(H2)]- providing additional evidence for differences in depletion patterns in those two lower-metallicity galaxies. We briefly discuss possible implications of these results for the interpretation of gas-phase abundances in quasi-stellar object absorption-line systems and of variations in the D/H ratio in the local Galactic interstellar medium.
- ID:
- ivo://CDS.VizieR/J/ApJS/228/11
- Title:
- Time-dependent cooling in photoionized plasma
- Short Name:
- J/ApJS/228/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I explore the thermal evolution and ionization states in gas cooling from an initially hot state in the presence of external photoionizing radiation. I compute the equilibrium and nonequilibrium cooling efficiencies, heating rates, and ion fractions for low-density gas cooling while exposed to the ionizing metagalactic background radiation at various redshifts (z=0-3), for a range of temperatures (10^8^-10^4^K), densities (10^-7^-10^3^cm^-3^), and metallicities (10^-3^-2 times solar). The results indicate the existence of a threshold ionization parameter, above which the cooling efficiencies are very close to those in photoionization equilibrium (so that departures from equilibrium may be neglected), and below which the cooling efficiencies resemble those in collisional time-dependent gas cooling with no external radiation (and are thus independent of density).
