- ID:
- ivo://CDS.VizieR/J/A+A/628/A71
- Title:
- CO spectra of 55 LIRGs and ULIRGs
- Short Name:
- J/A+A/628/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present IRAM-30m Telescope ^12^CO and ^13^CO observations of a sample of 55 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) in the local universe. This sample is a subset of the Great Observatory All-Sky LIRG Survey (GOALS), for which we use ancillary multi-wavelength data to better understand their interstellar medium and star formation properties. Fifty-three (96%) of the galaxies are detected in ^12^CO, and 29 (52%) are also detected in ^13^CO above a 3{sigma} level. The median full width at zero intensity (FWZI) velocity of the CO line emission is 661km/s, and 54% of the galaxies show a multi-peak CO profile. Herschel photometric data is used to construct the far-IR spectral energy distribution of each galaxy, which are fit with a modified blackbody model that allows us to derive dust temperatures and masses, and infrared luminosities. We make the assumption that the gas-to-dust mass ratio of (U)LIRGs is comparable to local spiral galaxies with a similar stellar mass (i.e., gas/dust of mergers is comparable to their progenitors) to derive a CO-to-H_2_ conversion factor of <{alpha}>=1.8^+1.3^_0.8_M_{sun}_/(K.km/s/pc^2^); such a value is comparable to that derived for (U)LIRGs based on dynamical mass arguments. We derive gas depletion times of 400-600Myr for the (U)LIRGs, compared to the 1.3Gyr for local spiral galaxies. Finally, we re-examine the relationship between the ^12^CO/^13^CO ratio and dust temperature, confirming a transition to elevated ratios in warmer systems.
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- ID:
- ivo://CDS.VizieR/J/A+A/629/A94
- Title:
- CO spectra of 49 semi-regular variables
- Short Name:
- J/A+A/629/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to study the main properties of a volume-limited unbiased sample of well characterized semi-regular variables (SRs) in order to clarify important issues that need to be further explained, such as the formation of axially symmetric planetary nebulae (PNe) from spherical circumstellar envelopes (CSEs) that takes place during the mass loss process along the AGB phase. We present new high S/N IRAM 30m observations of the ^12^CO J=2-1, ^12^CO J=1-0, and ^13^CO J=1-0 lines, in a volume-limited sample of SRs for which the Hipparcos distances are between 100-500 pc and declinations above -25{deg}. We analyzed the data by characterizing the main properties of the CSEs. The ^12^CO J=2-1 data have been used to study the profiles, while the ^12^CO J=1-0 data have been used to estimate mass-loss rates for the complete sample. Moreover, the ^12^CO J=2-1 line has been used to determine the possible structures responsible for such profiles. We have classified the sources into four groups according to the different profiles and final gas expansion velocities. Type 1 and 2 profiles are broad and narrow symmetric lines, respectively. Type 1 profiles, furthermore, are more related to standard spherically symmetric envelopes already studied. Type 3 profiles, on the contrary, are strange profiles with very pronounced asymmetries. Type 4 profiles, finally, are those which show two different components: a narrow line profile superimposed on a broad pedestal component. We find that for sources which show this kind of profile, with two different components, the variation amplitude is very low, what means that these SRs do not have a well developed inner envelope differentiated from the outer one. Interestingly, we report a moderate correlation between mass-loss rates and ^12^CO J=1-0/^12^CO J=2-1 line intensity ratios for O-rich SRs, suggesting a different behaviour between C- and O-rich SRs. By using SHAPE+shapemol, we find a unified simple model based on an oblate spheroid, placed in different orientations, that may explain all the ^12^CO profiles in the sample, indicating that the gas expansion is, in general, predominantly equatorial. Moreover, in order to explain the type 4 profiles, we define an extra component which may somehow be a biconical structure or similar according to the structures already found in this kind of sources. Type 1 and 2 profiles, curiously, may also be explained by standard spherically symmetric envelopes, but often requiring anomalously low velocities. Type 3 and 4 profiles, however, need axial symmetry to be explained. We conclude that most circumstellar shells around SRs show axial, strongly non-spherical symmetry. More interferometric observations are needed in order to make firm conclusions about mass-loss processes and possible morphologies of SRs.
- ID:
- ivo://CDS.VizieR/J/other/SciA/1.9
- Title:
- C/2014 Q2 (Lovejoy) spectra
- Short Name:
- J/other/SciA/1.9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The presence of numerous complex organic molecules (COMs; defined as those containing 6 or more atoms) around protostars shows that star formation is accompanied by an increase of molecular complexity. These COMs may be part of the material from which planetesimals and ultimately planets formed. Comets sample some of the oldest and most primitive material in the solar system, including ices, and are thus our best window into the volatile composition of the solar proto-planetary disk. Molecules identified to be present in cometary ices include water, simple hydrocarbons, oxygen, sulfur and nitrogen-bearing species, as well as a few COMs, such as ethylene glycol and glycine. Here, we report the detection of 21 molecules in comet C/2014 Q2 (Lovejoy), including the first identification of ethyl alcohol (ethanol, C2H5OH) and the simplest monosaccharide sugar glycolaldehyde (CH2OHCHO) in a comet. The abundances of ethanol and glycolaldehyde, respectively 5 and 0.8% relative to methanol (0.12 and 0.02% relative to water), are somewhat higher than values measured in solar-type protostars. Overall, the high abundance of COMs in cometary ices supports formation through grain-surface reactions in the solar system protoplanetary disk.
- ID:
- ivo://CDS.VizieR/J/ApJS/233/11
- Title:
- Cyanoacetylene (HC_3_N) infrared spectrum
- Short Name:
- J/ApJS/233/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HC_3_N is a ubiquitous molecule in interstellar environments, from external galaxies to Galactic interstellar clouds, star-forming regions, and planetary atmospheres. Observations of its rotational and vibrational transitions provide important information on the physical and chemical structures of the above environments. We present the most complete global analysis of the spectroscopic data of HC_3_N. We recorded the high-resolution infrared spectrum from 450 to 1350cm^-1^, a region dominated by the intense {nu}_5_ and {nu}_6_ fundamental bands, located at 660 and 500cm^-1^, respectively, and their associated hot bands. Pure rotational transitions in the ground and vibrationally excited states were recorded in the millimeter and submillimeter regions in order to extend the frequency range so far considered in previous investigations. All of the transitions from the literature and from this work involving energy levels lower than 1000cm^-1^ were fitted together to an effective Hamiltonian. Because of the presence of various anharmonic resonances, the Hamiltonian includes a number of interaction constants, in addition to the conventional rotational and vibrational l-type resonance terms. The data set contains about 3400 ro-vibrational lines of 13 bands and some 1500 pure rotational lines belonging to 12 vibrational states. More than 120 spectroscopic constants were determined directly from the fit, without any assumption deduced from theoretical calculations or comparisons with similar molecules. An extensive list of highly accurate rest frequencies was produced to assist astronomical searches and data interpretation. These improved data enabled a refined analysis of the ALMA observations toward Sgr B2(N2).
- ID:
- ivo://CDS.VizieR/J/ApJ/724/994
- Title:
- Cyano- to methanol and ammonia observations
- Short Name:
- J/ApJ/724/994
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of an effort to study gas-grain chemical models in star-forming regions as they relate to molecules containing cyanide (-C{\equiv}N) groups, we present here a search for the molecules 2-cyanoethanol (OHCH_2_CH_2_CN) and methoxyacetonitrile (CH_3_OCH_2_CN) in the galactic center region SgrB2. These species are structural isomers of each other and are targeted to investigate the cross-coupling of pathways emanating from the photolysis products of methanol and ammonia with pathways involving cyano-containing molecules. Methanol and ammonia ices are two of the main repositories of the elements C, O, and N in cold clouds and understanding their link to cyanide chemistry could give important insights into prebiotic molecular evolution. Neither species was positively detected, but the upper limits we determined allow comparison to the general patterns gleaned from chemical models. Our results indicate the need for an expansion of the model networks to better deal with cyano-chemistry, in particular with respect to pathways including products of methanol photolysis. In addition to these results, the two main observational routes for detecting new interstellar molecules are discussed.
- ID:
- ivo://CDS.VizieR/J/ApJS/158/188
- Title:
- Detection of glycolaldehyde toward Sgr B2
- Short Name:
- J/ApJS/158/188
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Glycolaldehyde (CHOCH_2_OH), the simplest two-carbon {alpha}-hydroxy aldehyde, has become of great interest in the field of astrochemistry due to its recent detection toward the Sagittarius B2 (N-LMH) molecular cloud. The original interstellar identification was based on an extrapolation of prior microwave rotational spectroscopy of glycolaldehyde. The millimeter and submillimeter spectra of this molecule from 128 to 354GHz were subsequently measured after the interstellar detection. We present here the millimeter spectrum of this molecule from 72 to 122.5GHz along with a combined millimeter and submillimeter pure rotational analysis of the ground and the first three vibrationally excited states of glycolaldehyde that enables a more complete molecular partition function to be determined.
- ID:
- ivo://CDS.VizieR/J/ApJ/734/98
- Title:
- DISCS. II. Southern sky disk data
- Short Name:
- J/ApJ/734/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second in a series of papers based on data from DISCS, a Submillimeter Array observing program aimed at spatially and spectrally resolving the chemical composition of 12 protoplanetary disks. We present data on six Southern sky sources -IM Lup, SAO 206462 (HD 135344b), HD 142527, AS 209, AS 205, and V4046 Sgr- which complement the six sources in the Taurus star-forming region reported previously. CO 2-1 and HCO^+^ 3-2 emission are detected and resolved in all disks and show velocity patterns consistent with Keplerian rotation. Where detected, the emission from DCO^+^ 3-2, N_2_H^+^ 3-2, H_2_CO 3_0 3_-2_0 2_ and 4_1 4_-3_1 3_, HCN 3-2, and CN 2_3 3/4/2_-1_2 2/3/1_ are also generally spatially resolved. The detection rates are highest toward the M and K stars, while the F star SAO 206462 has only weak CN and HCN emission, and H2CO alone is detected toward HD 142527.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/480
- Title:
- DISCS. I. Taurus protoplanetary disk data
- Short Name:
- J/ApJ/720/480
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chemistry plays an important role in the structure and evolution of protoplanetary disks, with implications for the composition of comets and planets. This is the first of a series of papers based on data from DISCS (Disk Imaging Survey of Chemistry with SMA), a Submillimeter Array survey of the chemical composition of protoplanetary disks. The six Taurus sources in the program (DM Tau, AA Tau, LkCa 15, GM Aur, CQ Tau, and MWC 480) range in stellar spectral type from M1 to A4 and offer an opportunity to test the effects of stellar luminosity on the disk chemistry. The disks were observed in 10 different lines at ~3" resolution and an rms of ~100mJy/beam at ~0.5km/s.
- ID:
- ivo://CDS.VizieR/J/AJ/138/1380
- Title:
- Dust clumps in the Galactic Plane
- Short Name:
- J/AJ/138/1380
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present imaging observations of continuum emission from interstellar dust at 850 and 1200um of a section of the Galactic Plane covering 2deg^2^ centered at l=44{deg}. Complementary jiggle-mapping and fast-scanning techniques were used, respectively, at these two wavelengths. The mapped area includes the well-known star formation regions W49 and G45.1/45.5. Using an automated clump-finding routine, we identify 132 compact 850um emission features within the region above a completeness level of about 200mJy/beam. The positions of the latter objects were used to determine fluxes from the 1200um image. Spectral line data were subsequently obtained with the same observing beamwidth as at 850um for almost half of the objects; these were either imaged in the ^13^CO (3-2) line, or basic characteristics determined using the ^12^CO (3-2) transition. We use these data, supplemented by existing ^13^CO (1-0) and HI survey data, to determine distances and hence derive masses for the dust clump ensemble, assuming a uniform dust temperature of 15K. From these data we find that the number-mass relationship for clumps in the field is similar to that found for individual star-forming regions.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A104
- Title:
- [ESS2003] Q2343-BX610 reduced PdBI spectra
- Short Name:
- J/A+A/628/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Plateau De Bure Interferometer to observe multiple CO and neutral carbon transitions in a z=2.2 main sequence disk galaxy, BX610. Our observation of CO(7-6), CO(4-3) and both far infrared [CI] lines complements previous observations of H-alpha and low-J CO, and reveal a galaxy that is vigorously forming stars with UV fields, (Log(G/G_0_)<3.25), less extreme than local ULIRGs or most starbursting submillimeter galaxies in the early universe. Our observations allow new independent estimates of the cold gas mass which indicate M_gas_~2x10^11^M_{sun}_, and suggest a modestly larger alpha_CO value of ~8.2. The corresponding gas depletion timescale is ~1.5Gyr. In addition to gas of modest density (Log(n[cm^-3^])<3) heated by star formation, BX610 shows evidence for a significant second gas component responsible for the strong high-J CO emission. This second component might either be a high density molecular gas component heated by star formation in a typical photodissociation region, or it could be molecular gas excited by low velocity C shocks. The CO(7-6) to far infrared luminosity ratio we observe is significantly higher than typical star forming galaxies and suggests that CO(7-6) is not a reliable star formation tracer in this galaxy.
