- ID:
- ivo://CDS.VizieR/J/ApJS/112/557
- Title:
- Classification of IRAS Sources
- Short Name:
- J/ApJS/112/557
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IRAS low-resolution spectra were extracted for 11,224 IRAS sources. These spectra were classified into astrophysical classes, based on the presence of emission and absorption features and on the shape of the continuum. Counterparts of these IRAS sources in existing optical and infrared catalogs are identified, and their optical spectral types are listed if they are known. The correlations between the photospheric/ optical and circumstellar/infrared classifications are discussed.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/830/127
- Title:
- CLASSy: CARMA obs. in L1451 region of Perseus
- Short Name:
- J/ApJ/830/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a 3mm spectral line and continuum survey of L1451 in the Perseus Molecular Cloud. These observations are from the CARMA Large Area Star Formation Survey (CLASSy), which also imaged Barnard 1, NGC1333, Serpens Main, and Serpens South. L1451 is the survey region with the lowest level of star formation activity-it contains no confirmed protostars. HCO^+^, HCN, and N_2_H^+^ (J=1->0) are all detected throughout the region, with HCO^+^ being the most spatially widespread, and molecular emission seen toward 90% of the area above N(H_2_) column densities of 1.9x10^21^cm^-2^. HCO^+^ has the broadest velocity dispersion, near 0.3km/s on average, compared with ~0.15km/s for the other molecules, thus representing a range of subsonic to supersonic gas motions. Our non-binary dendrogram analysis reveals that the dense gas traced by each molecule has a similar hierarchical structure, and that gas surrounding the candidate first hydrostatic core (FHSC), L1451-mm, and other previously detected single-dish continuum clumps has similar hierarchical structure; this suggests that different subregions of L1451 are fragmenting on the pathway to forming young stars. We determined that the three-dimensional morphology of the largest detectable dense-gas structures was relatively ellipsoidal compared with other CLASSy regions, which appeared more flattened at the largest scales. A virial analysis shows that the most centrally condensed dust structures are likely unstable against collapse. Additionally, we identify a new spherical, centrally condensed N_2_H^+^ feature that could be a new FHSC candidate. The overall results suggest that L1451 is a young region starting to form its generation of stars within turbulent, hierarchical structures.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/172
- Title:
- Cloud-scale molecular gas properties in 15 galaxies
- Short Name:
- J/ApJ/860/172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the velocity dispersion, {sigma}, and surface density, {Sigma}, of the molecular gas in nearby galaxies from CO spectral line cubes with spatial resolution 45-120pc, matched to the size of individual giant molecular clouds. Combining 11 galaxies from the PHANGS-ALMA survey with four targets from the literature, we characterize ~30000 independent sightlines where CO is detected at good significance. {Sigma} and {sigma} show a strong positive correlation, with the best-fit power-law slope close to the expected value for resolved, self-gravitating clouds. This indicates only a weak variation in the virial parameter {alpha}_vir_{propto}{sigma}^2^/{Sigma}, which is ~1.5-3.0 for most galaxies. We do, however, observe enormous variation in the internal turbulent pressure P_turb_{propto}{Sigma}{sigma}^2^, which spans ~5dex across our sample. We find {Sigma}, {sigma}, and P_turb_ to be systematically larger in more massive galaxies. The same quantities appear enhanced in the central kiloparsec of strongly barred galaxies relative to their disks. Based on sensitive maps of M31 and M33, the slope of the {sigma}-{Sigma} relation flattens at {Sigma}<~10M_{sun}_/pc^2^, leading to high {sigma} for a given {Sigma} and high apparent {alpha}_vir_. This echoes results found in the Milky Way and likely originates from a combination of lower beam-filling factors and a stronger influence of local environment on the dynamical state of molecular gas in the low-density regime.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A124
- Title:
- Clouds in SEDIGISM science demonstration field
- Short Name:
- J/A+A/601/A124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin and life-cycle of molecular clouds are still poorly constrained, despite their importance for understanding the evolution of the interstellar medium. Many large-scale surveys of the Galactic plane have been conducted recently, allowing for rapid progress in this field. Nevertheless, a sub-arcminute resolution global view of the large-scale distribution of molecular gas, from the diffuse medium to dense clouds and clumps, and of their relationship to the spiral structure, is still missing. We have carried out a systematic, homogeneous, spectroscopic survey of the inner Galactic plane, in order to complement the many continuum Galactic surveys available with crucial distance and gas-kinematic information. Our aim is to combine this data set with recent infrared to sub-millimetre surveys at similar angular resolutions. The SEDIGISM survey covers 78deg^2^ of the inner Galaxy (-60{deg}<l<+18{deg}, |b|<0.5{deg}) in the J=2-1 rotational transition of ^13^CO. This isotopologue of CO is less abundant than ^12^CO by factors up to 100. Therefore, its emission has low to moderate optical depths, and higher critical density, making it an ideal tracer of the cold, dense interstellar medium. The data have been observed with the SHFI single-pixel instrument at APEX. The observational setup covers the ^13^CO(2-1) and C^18^O(2-1) lines, plus several transitions from other molecules. The observations have been completed. Data reduction is in progress and the final data products will be made available in the near future. Here we give a detailed description of the survey and the dedicated data reduction pipeline. To illustrate the scientific potential of this survey, preliminary results based on a science demonstration field covering -20{deg}<l<-18.5{deg} are presented. Analysis of the ^13^CO(2-1) data in this field reveals compact clumps, diffuse clouds, and filamentary structures at a range of heliocentric distances. By combining our data with data in the (1-0) transition of CO isotopologues from the ThrUMMS survey, we are able to compute a 3D realization of the excitation temperature and optical depth in the interstellar medium. Ultimately, this survey will provide a detailed, global view of the inner Galactic interstellar medium at an unprecedented angular resolution of ~30".
- ID:
- ivo://CDS.VizieR/J/ApJ/703/736
- Title:
- Clump properties in the LMC 30 Dor region
- Short Name:
- J/ApJ/703/736
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a complete ^12^CO(J=1-0) map of the prominent molecular ridge in the Large Magellanic Cloud (LMC) obtained with the 22m ATNF Mopra Telescope. The region stretches southward by ~2{deg} (or 1.7kpc) from 30 Doradus, the most vigorous star-forming region in the Local Group. The location of this molecular ridge is unique insofar as it allows us to study the properties of molecular gas as a function of the ambient radiation field in a low-metallicity environment. The mass spectrum and the scaling relations between the properties of the CO clumps in the molecular ridge are similar, but not identical, to those that have been established for Galactic molecular clouds.
- ID:
- ivo://CDS.VizieR/J/ApJ/625/891
- Title:
- Clumps in NGC 7538 at 450 and 850{mu}m
- Short Name:
- J/ApJ/625/891
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present submillimeter continuum maps at 450 and 850{mu}m of a 12'x8' region of the NGC 7538 high-mass star-forming region, made using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. We used an automated clump-finding algorithm to identify 67 clumps in the 450{mu}m image and 77 in the 850{mu}m image.
- ID:
- ivo://CDS.VizieR/J/AJ/136/2083
- Title:
- Clumps in NGC 6334 from 450/850um observations
- Short Name:
- J/AJ/136/2083
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6334 is a galactic star-forming region in Scorpius, heavily obscured by intervening dust. The region consists of several major sites of star formation known previously from far-infrared (IR) and radio-wavelength observations. We present images of NGC 6334 obtained at wavelengths of 850 and 450um with the Submillimeter Common-User Bolometric Array at the James Clerk Maxwell Telescope. These data highlight the distribution of dense cold dust, a particularly striking feature of which is a narrow ridge of emission passing between most of the star-forming centers. We use a clump-finding technique to quantify the distribution of dust emission throughout the region, and we obtain estimates of the sizes, masses, and temperatures of the clump ensemble under simple assumptions.
- ID:
- ivo://CDS.VizieR/J/A+A/610/A12
- Title:
- Clustering the Orion B giant molecular cloud
- Short Name:
- J/A+A/610/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous attempts at segmenting molecular line maps of molecular clouds have focused on using position-position-velocity data cubes of a single molecular line to separate the spatial components of the cloud. In contrast, wide field spectral imaging over a large spectral bandwidth in the (sub)mm domain now allows one to combine multiple molecular tracers to understand the different physical and chemical phases that constitute giant molecular clouds (GMCs). We aim at using multiple tracers (sensitive to different physical processes and conditions) to segment a molecular cloud into physically/ chemically similar regions (rather than spatially connected components), thus disentangling the different physical/chemical phases present in the cloud. We use a machine learning clustering method, namely the Meanshift algorithm, to cluster pixels with similar molecular emission, ignoring spatial information. Clusters are defined around each maximum of the multidimensional probability density function (PDF) of the line integrated intensities. Simple radiative transfer models were used to interpret the astrophysical information uncovered by the clustering analysis. A clustering analysis based only on the J=1-0 lines of three isotopologues of CO proves sufficient to reveal distinct density/column density regimes (n_H_~100cm^-3^, ~500cm^-3^, and >1000cm^-3^), closely related to the usual definitions of diffuse, translucent and high-column-density regions. Adding two UV-sensitive tracers, the J=1-0 line of HCO^+^ and the N=1-0 line of CN, allows us to distinguish two clearly distinct chemical regimes, characteristic of UV-illuminated and UV-shielded gas. The UV-illuminated regime shows overbright HCO^+^ and CN emission, which we relate to a photochemical enrichment effect. We also find a tail of high CN/HCO^+^ intensity ratio in UV-illuminated regions. Finer distinctions in density classes (n_H_~710^3^cm^-3^, ~410^4^cm^-3^) for the densest regions are also identified, likely related to the higher critical density of the CN and HCO^+^ (1-0) lines. These distinctions are only possible because the high-density regions are spatially resolved. Molecules are versatile tracers of GMCs because their line intensities bear the signature of the physics and chemistry at play in the gas. The association of simultaneous multi-line, wide-field mapping and powerful machine learning methods such as the Meanshift clustering algorithm reveals how to decode the complex information available in these molecular tracers.
- ID:
- ivo://CDS.VizieR/J/ApJS/227/25
- Title:
- 6 & 1.3cm deep VLA obs. toward 58 high-mass SFRs
- Short Name:
- J/ApJS/227/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high-sensitivity radio continuum survey at 6 and 1.3cm using the Karl G. Jansky Very Large Array toward a sample of 58 high-mass star-forming regions. Our sample was chosen from dust clumps within infrared dark clouds with and without IR sources (CMC-IRs and CMCs, respectively), and hot molecular cores (HMCs), with no previous, or relatively weak radio continuum detection at the 1mJy level. Due to the improvement in the continuum sensitivity of the Very Large Array, this survey achieved map rms levels of ~3-10{mu}Jy/beam at sub-arcsecond angular resolution. We extracted 70 continuum sources associated with 1.2mm dust clumps. Most sources are weak, compact, and prime candidates for high-mass protostars. Detection rates of radio sources associated with the millimeter dust clumps for CMCs, CMC-IRs, and HMCs are 6%, 53%, and 100%, respectively. This result is consistent with increasing high-mass star formation activity from CMCs to HMCs. The radio sources located within HMCs and CMC-IRs occur close to the dust clump centers, with a median offset from it of 12000au and 4000au, respectively. We calculated 5-25GHz spectral indices using power-law fits and obtained a median value of 0.5 (i.e., flux increasing with frequency), suggestive of thermal emission from ionized jets. In this paper we describe the sample, observations, and detections.
- ID:
- ivo://CDS.VizieR/J/A+A/581/A48
- Title:
- 1.3cm line survey toward Orion KL
- Short Name:
- J/A+A/581/A48
- Date:
- 18 Nov 2021 11:23:37
- Publisher:
- CDS
- Description:
- Orion KL has served as a benchmark for spectral line searches throughout the (sub)millimeter regime. The main goal is to systematically study spectral characteristics of Orion KL in the 1.3cm band. We carried out a spectral line survey (17.9GHz to 26.2GHz) with the Effelsberg-100m telescope towards Orion KL. We find 261 spectral lines, yielding an average line density of about 32 spectral features per GHz above 3 sigma. The identified lines include 164 radio recombination lines (RRLs) and 97 molecular lines. A total of 23 molecular transitions from species known to exist in Orion KL are detected for the first time in the interstellar medium. Non-metastable ^15^NH_3_ transitions are detected in Orion KL for the first time. Based on the velocity information of detected lines and the ALMA images, the spatial origins of molecular emission are constrained and discussed. A narrow feature is found in SO_2_ (8_1,7_-7_2,6_), possibly suggesting the presence of a maser line. Column densities and fractional abundances relative to H_2_ are estimated for 12 molecules with LTE methods. Rotational diagrams of non-metastable ^14^NH_3_ transitions with J=K+1 to J=K+4 yield different results; metastable ^15^NH_3_ is found to have a higher excitation temperature than non-metastable ^15^NH_3_, indicating that they may trace different regions. Elemental and isotopic abundance ratios are estimated: ^12^C/^13^C=63+/-17, ^14^N/^15^N=100+/-51, D/H=0.0083+/-0.0045. The dispersion of the He/H ratios derived from H_alpha/He_alpha_ pairs to H_delta_/He_delta_ pairs is very small, which is consistent with theoretical predictions that the departure coefficients bn factors for hydrogen and helium are nearly identical. Based on a non-LTE code neglecting excitation by the infrared radiation field and a likelihood analysis, we find that the denser regions have lower kinetic temperature, which favors an external heating of the Hot Core.
