- ID:
- ivo://CDS.VizieR/J/A+A/642/A206
- Title:
- Propynethial (HCCCHS) submm spectroscopy
- Short Name:
- J/A+A/642/A206
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The majority of sulfur-containing molecules detected in the interstellar medium (ISM) are analogs of oxygen-containing compounds. Propynal was detected in the ISM in 1988, hence propynethial, its sulfur derivative, is a good target for an ISM search. Our aim is to measure the rotational spectrum of propynethial and use those measurements to search for this species in the ISM. To date, measurements of the rotational spectra of propynethial have been limited to a small number or transitions below 52GHz. The extrapolation of the prediction to lines in the milimeter-wave domain is inaccurate and does not provide data to permit an unambiguous detection. The rotational spectrum was re-investigated up to 630GHz. Using the new prediction lines of propynethial, as well as the related propynal, a variety of astronomical sources were searched, including star-forming regions and dark clouds. A total of 3288 transitions were newly assigned and fit together with those from previous studies, reaching quantum numbers up to J=107 and K_a_=24. Watson's symmetric top Hamiltonian in the I^r^ representation was used for the analysis, because the molecule is very close to the prolate limit. The search for propynethial resulted in a non-detection; upper limits to the column density were derived in each source.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/588/L8
- Title:
- Protonated formaldehyde in L1689B
- Short Name:
- J/A+A/588/L8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Complex organic molecules (COMs) are detected in many regions of the interstellar medium, including prestellar cores. However, their formation mechanisms in cold (~10K) cores remain to this date poorly understood. The formyl radical HCO is an important candidate precursor for several O-bearing terrestrial COMs in cores, as an abundant building block of many of these molecules. Several chemical routes have been proposed to account for its formation, both on grain surfaces, as an incompletely hydrogenated product of H addition to frozen-out CO molecules, or in the gas phase, either the product of the reaction between H_2_CO and a radical, or as a product of dissociative recombination of protonated formaldehyde H_2_COH^+^. The detection and abundance determination of H_2_COH^+^, if present, could provide clues as to whether this latter scenario might apply. We searched for protonated formaldehyde H_2_COH^+^ in the prestellar core L1689B using the IRAM 30m telescope. The H_2_COH^+^ ion is unambiguously detected, for the first time in a cold (~10K) source. The derived abundance agrees with a scenario in which the formation of H_2_COH^+^ results from the protonation of formaldehyde. We use this abundance value to constrain the branching ratio of the dissociative recombination of H2COH+ towards the HCO channel to ~10-30%. This value could however be smaller if HCO can be efficiently formed from gas-phase neutral- neutral reactions, and we stress the need for laboratory measurements of the rate constants of these reactions at 10K. Given the experimental difficulties in measuring branching ratios experimentally, observations can bring valuable constraints on these values, and provide a useful input for chemical networks.
723. Protostellar cores
- ID:
- ivo://CDS.VizieR/J/A+A/291/943
- Title:
- Protostellar cores
- Short Name:
- J/A+A/291/943
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Basing on the coagulation model of Ossenkopf (1993A&A...280..617O), we systematically computed and tabulated the opacity of dust in dense protostellar cores between 1 micrometers and 1.3 mm. The possible physical conditions were varied especially considering the influence of different gas densities and molecular depletion ratios. In comparison to the dust opacity in the diffuse interstellar medium, we found nowhere changes by more than the factor 5 for ice-covered dust grains. Possible uncertainties and deviations in environments with different physical conditions are discussed. Although one may imagine very special situations in which the dust opacity is changed by more than a factor 10, for physically reasonable conditions in dense protostellar cores, all possible deviations from the tabulated values may not sum up to more than a factor of 2. Using these tables of dust opacities, the submm continuum radiation of cold dust in protostellar cores is a good tracer of their total mass.
- ID:
- ivo://CDS.VizieR/J/other/Sci/345.791
- Title:
- Pseudo-3D maps of DIB at 862nm
- Short Name:
- J/other/Sci/345.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The diffuse interstellar bands (DIBs) are absorption lines observed in visual and near-infrared spectra of stars. Understanding their origin in the interstellar medium is one of the oldest problems in astronomical spectroscopy, as DIBs have been known since 1922. In a completely new approach to understanding DIBs, we combined information from nearly 500,000 stellar spectra obtained by the massive spectroscopic survey RAVE (Radial Velocity Experiment) to produce the first pseudo-three-dimensional map of the strength of the DIB at 8620 angstroms covering the nearest 3 kiloparsecs from the Sun, and show that it follows our independently constructed spatial distribution of extinction by interstellar dust along the Galactic plane. Despite having a similar distribution in the Galactic plane, the DIB 8620 carrier has a significantly larger vertical scale height than the dust. Even if one DIB may not represent the general DIB population, our observations outline the future direction of DIB research.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/1965
- Title:
- Radial dust properties of SINGS galaxies
- Short Name:
- J/ApJ/701/1965
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of the radial distribution of dust properties in the SINGS sample, performed on a set of ultraviolet (UV), infrared (IR), and HI surface brightness profiles, combined with published molecular gas profiles and metallicity gradients. By applying physical dust models to our radial spectral energy distributions, we have derived radial profiles of the total dust mass surface density, the fraction of the total dust mass contributed by polycyclic aromatic hydrocarbons (PAHs), and the intensity of the radiation field heating the grains.
- ID:
- ivo://CDS.VizieR/J/ApJ/858/90
- Title:
- Radial profiles of 5 nearby galaxies
- Short Name:
- J/ApJ/858/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use new ALMA observations to investigate the connection between dense gas fraction, star formation rate (SFR), and local environment across the inner region of four local galaxies showing a wide range of molecular gas depletion times. We map HCN(1-0), HCO^+^(1-0), CS(2-1), ^13^CO(1-0), and C^18^O(1-0) across the inner few kiloparsecs of each target. We combine these data with short-spacing information from the IRAM large program EMPIRE, archival CO maps, tracers of stellar structure and recent star formation, and recent HCN surveys by Bigiel+ (2016ApJ...822L..26B) and Usero+ (2015AJ....150..115U). We test the degree to which changes in the dense gas fraction drive changes in the SFR. I_HCN_/I_CO_ (tracing the dense gas fraction) correlates strongly with I_CO_ (tracing molecular gas surface density), stellar surface density, and dynamical equilibrium pressure, P_DE_ (Elmegreen 1989ApJ...338..178E). Therefore, I_HCN_/I_CO_ becomes very low and HCN becomes very faint at large galactocentric radii, where ratios as low as I_HCN_/I_CO_~0.01 become common. The apparent ability of dense gas to form stars, {Sigma}_SFR_/{Sigma}_dense_ (where {Sigma}_dense_ is traced by the HCN intensity and the star formation rate is traced by a combination of H{alpha} and 24{mu}m emission), also depends on environment. {Sigma}_SFR_/{Sigma}_dense_ decreases in regions of high gas surface density, high stellar surface density, and high P_DE_. Statistically, these correlations between environment and both {Sigma}_SFR_/{Sigma}_dense_ and I_HCN_/I_CO_ are stronger than that between apparent dense gas fraction (I_HCN_/I_CO_) and the apparent molecular gas star formation efficiency {Sigma}_SFR_/{Sigma}_mol_. We show that these results are not specific to HCN.
- ID:
- ivo://CDS.VizieR/J/ApJ/901/51
- Title:
- Radio continuum param. of Galactic HII regions
- Short Name:
- J/ApJ/901/51
- Date:
- 15 Feb 2022 14:31:45
- Publisher:
- CDS
- Description:
- Sgr E is a massive star formation complex found toward the Galactic center that consists of numerous discrete, compact HII regions. It is located at the intersection between the central molecular zone (CMZ) and the far dust lane of the Galactic bar, similar to "hot spots" seen in external galaxies. Compared with other Galactic star formation complexes, the Sgr E complex is unusual because its HII regions all have similar radio luminosities and angular extents, and they are deficient in ~10{mu}m emission from their photodissociation regions (PDRs). Our Green Bank Telescope radio recombination line observations increase the known membership of Sgr E to 19 HII regions. There are 43 additional HII region candidates in the direction of Sgr E, 26 of which are detected for the first time here using MeerKAT 1.28GHz data. Therefore, the true HII region population of Sgr E may number >60. Using APEX SEDIGISM ^13^CO 2->1 data we discover a 3.0x10^5^M_{sun}_ molecular cloud associated with Sgr E, but find few molecular or far-infrared concentrations at the locations of the Sgr E HII regions. Comparison with simulations and an analysis of its radio continuum properties indicate that Sgr E formed upstream in the far dust lane of the Galactic bar a few million years ago and will overshoot the CMZ, crashing into the near dust lane. We propose that the unusual infrared properties of the Sgr E HII regions are caused by their orbits about the Galactic center, which have possibly stripped their PDRs.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A21
- Title:
- Radio cubes of G82.65-2.00
- Short Name:
- J/A+A/608/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The combination of line and continuum observations can provide vital insight into the formation and fragmentation of filaments and the initial conditions for star formation. We have carried out line observations to map the kinematics of an evolved, actively star forming filament G82.65-2.00. The filament was first identified from the Planck data as a region of particularly cold dust emission and was mapped at 100-500m as a part of the Herschel key program Galactic Cold Cores. The Herschel observations cover the central part of the filament, corresponding to a filament length of ~12pc at the assumed distance of 620pc. CO observations show that the filament has an intriguing velocity field with several velocity components around the filament. In this paper, we study the velocity structure in detail, to quantify possible mass accretion rate onto the filament, and study the masses of the cold cores located in the filament. We have carried out line observations of several molecules, including CO isotopologues, HCO^+^, HCN, and CS with the Osaka 1.85m telescope and the Nobeyama 45m telescope. The spectral line data are used to derive velocity and column density information.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A69
- Title:
- Radio observations of G074.11+00.11
- Short Name:
- J/A+A/630/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present molecular line and dust continuum observations of a Planck-detected cold cloud, G074.11+00.11. The cloud consists of a system of curved filaments and a central star-forming clump. The clump is associated with several infrared sources and H_2_O maser emission. We aim to determine the mass distribution and gas dynamics within the clump, to investigate if the filamentary structure seen around the clump repeats itself on a smaller scale, and to estimate the fractions of mass contained in dense cores and filaments. The velocity distribution of pristine dense gas can be used to investigate the global dynamical state of the clump, the role of filamentary inflows, filament fragmentation and core accretion. We use molecular line and continuum observations from single dish observatories and interferometry facilities to study the kinematics of the region. The molecular line observations show that the central clump may have formed as a result of a large-scale filament collision. The central clump contains three compact cores. Assuming a distance of 2.3kpc, based on Gaia observations and a three-dimensional extinction method of background stars, the mass of the central clump exceeds 700 solar masses, which is roughly 25% of the total mass of the cloud. Our virial analysis suggests that the central clump and all identified substructures are collapsing. We find no evidence for small-scale filaments associated with the cores. Our observations indicate that the clump is fragmented into three cores with masses in the range of [10,50] solar masses and that all three are collapsing. The presence of an H_2_O maser emission suggests active star formation. However the CO lines show only weak signs of outflows. We suggest that the region is young and any processes leading to star formation have just recently begun.
- ID:
- ivo://CDS.VizieR/J/ApJS/221/26
- Title:
- Radio observations of Galactic WISE HII regions
- Short Name:
- J/ApJS/221/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The WISE Catalog of Galactic H II Regions contains ~2000 H II region candidates lacking ionized gas spectroscopic observations. All candidates have the characteristic H II region mid-infrared morphology of WISE 12{mu}m emission surrounding 22{mu}m emission, and additionally have detected radio continuum emission. We here report Green Bank Telescope hydrogen radio recombination line (RRL) and radio continuum detections in the X-band (9GHz; 3cm) of 302 WISE H II region candidates (out of 324 targets observed) in the zone 225{deg}>=l>=-20{deg}, |b|<=6{deg}. Here we extend the sky coverage of our H II region Discovery Survey, which now contains nearly 800 HII regions distributed across the entire northern sky. We provide LSR velocities for the 302 detections and kinematic distances for 131 of these. Of the 302 new detections, 5 have (l, b, v) coordinates consistent with the Outer Scutum-Centaurus Arm (OSC), the most distant molecular spiral arm of the Milky Way. Due to the Galactic warp, these nebulae are found at Galactic latitudes >1{deg} in the first Galactic quadrant, and therefore were missed in previous surveys of the Galactic plane. One additional region has a longitude and velocity consistent with the OSC but lies at a negative Galactic latitude (G039.183-01.422; -54.9km/s). With Heliocentric distances >22kpc and Galactocentric distances >16kpc, the OSC H II regions are the most distant known in the Galaxy. We detect an additional three HII regions near ~=150{deg} whose LSR velocities place them at Galactocentric radii >19kpc. If their distances are correct, these nebulae may represent the limit to Galactic massive star formation.