- ID:
- ivo://CDS.VizieR/J/PASJ/51/791
- Title:
- Molecular clouds in southern HII regions
- Short Name:
- J/PASJ/51/791
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out extensive ^13^CO(J=1-0) observations toward 23 southern H II regions associated with bright-rimmed clouds. In total, 95 molecular clouds have been identified to be associated with the H II regions. Among the 95, 57 clouds are found to be associated with 204 IRAS point sources which are candidates for young stellar objects. There is a significant increase of star-formation efficiency on the side facing to the H II regions; the luminosity-to-mass ratio, defined as the ratio of the stellar luminosity to the molecular cloud mass, is higher by an order of magnitude on the near side of the H II regions than that on the. far side. This indicates that molecular gas facing to the H II regions is more actively forming massive stars whose luminosity is ~>10^3^L_{sun}_. In addition, the number density of the IRAS point sources increases by a factor of 2 on the near side of the H II regions compared with on the far side. These results strongly suggest that the active formation of massive stars on the near side of the H II regions is due to the effects of the H II regions, such as the compression of molecular material by the ionization/shock fronts. For the whole Galaxy, we estimate that the present star-formation rate under such effects is at least 0.2-0.4M_{sun}_/yr, corresponding to a few 10% by mass.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/570/A109
- Title:
- Molecular gas associated with IRAS 10361-5830
- Short Name:
- J/A+A/570/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the distribution of the molecular gas and dust in the molecular clump linked to IRAS 10361-5830, located in the environs of the bubble-shaped HII region Gum 31 in the Carina region, with the aim of determining the main parameters of the associated material and of investigating the evolutionary state of the young stellar objects identified there.
- ID:
- ivo://CDS.VizieR/J/A+A/540/A96
- Title:
- Molecular gas in Hickson Compact Groups
- Short Name:
- J/A+A/540/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the effect of the extreme environment in Hickson Compact Groups (HCGs) on the molecular gas mass, M_H2_, and the star formation rate (SFR) of galaxies as a function of atomic hydrogen (HI) content and evolutionary phase of the group. We selected a redshift-limited (D<100Mpc) sample of 88 galaxies in 20 HCGs with available atomic hydrogen (HI) VLA maps, covering a wide range of HI deficiencies and evolutionary phases of the groups containing at least one spiral galaxy. We observed the CO(1-0) and CO(2-1) lines with the IRAM 30m telescope for 47 galaxies. Together with literature data, our sample contains CO(1-0) spectra for 86 galaxies. We derived the far-infrared (FIR) luminosity L_FIR_ from IRAS data and used it as a tracer of the star formation rate (SFR). We calculated the HI mass, M_HI_ L_FIR_ and M_H2_ deficiencies, based on the values expected from L_B_ and L_K_ in isolated galaxies from the AMIGA sample. We limited our statistical analysis to spiral galaxies, since the large number of upper limits did not allow drawing strong conclusions about M_H2_ and L_FIR_ in early-type galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/710/150
- Title:
- Molecular lines in EGOs
- Short Name:
- J/ApJ/710/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first systematic survey of molecular lines (including HCO^+^(1-0) and ^12^CO, ^13^CO, C^18^O(1-0) lines at the 3mm band) toward a new sample of 88 massive young stellar object (MYSO) candidates associated with ongoing outflows (known as extended green objects or EGOs) identified from the Spitzer GLIMPSE survey in the northern hemisphere with the Purple Mountain Observatory 13.7m radio telescope. By analyzing the asymmetries of the optically thick line HCO^+^ for 69 of 72 EGOs with HCO^+^ detection, we found 29 sources with "blue asymmetric profiles" and 19 sources with "red asymmetric profiles."
- ID:
- ivo://CDS.VizieR/J/A+A/504/853
- Title:
- Molecular lines in 5 massive dense cores
- Short Name:
- J/A+A/504/853
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two mid-infrared quiet and two brighter massive cores were observed in various transitions (E_up_ up to 289K) of CS, OCS, H_2_S, SO, and SO_2_ and of their ^34^S isotopologues at mm wavelengths with the IRAM 30m and CSO telescopes. The 1D modeling of the dust continuum is used to derive the density and temperature laws, which were then applied in the RATRAN code to modeling the observed line emission and to deriving the relative abundances of the molecules. All lines are detected, except the highest energy SO_2_ transition. Infall (up to 2.9km/s) may be detected towards the core W43MM1. We propose an evolutionary sequence of our sources (W43MM1 - IRAS18264-1152 - IRAS05358+3543 - IRAS18162-2048), based on the SED analysis. The analysis of the variations in abundance ratios from source to source reveals that the SO and SO_2_ relative abundances increase with time, while CS and OCS decrease. Molecular ratios, such as [OCS/H_2_S], [CS/H_2_S], [SO/OCS], [SO_2_/OCS], [CS/SO], and [SO_2_/SO] may be good indicators of evolution, depending on layers probed by the observed molecular transitions. Observations of molecular emission from warmer layers, so that involving higher upper energy levels must be included.
- ID:
- ivo://CDS.VizieR/J/ApJ/780/85
- Title:
- Molecular line study of infrared dark clouds
- Short Name:
- J/ApJ/780/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is currently assumed that infrared dark clouds (IRDCs) represent the earliest evolutionary stages of high-mass stars (>8M_{sun}_). Submillimeter and millimeter-wave studies performed over the past 15yr show that IRDCs possess a broad variety of properties, and hence a wide range of problems and questions that can be tackled. In this paper, we report an investigation of the molecular composition and chemical processes in two groups of IRDCs. Using the Mopra, APEX, and IRAM radio telescopes over the last four years, we have collected molecular line data for CO, H_2_CO, HNCO, CH_3_CCH, CH_3_OH, CH_3_CHO, CH_3_OCHO, and CH_3_OCH_3_. For all of these species we estimated molecular abundances. We then undertook chemical modeling studies, concentrating on the source IRDC028.34+0.06, and compared observed and modeled abundances. This comparison showed that to reproduce observed abundances of complex organic molecules, a zero-dimensional gas-grain model with constant physical conditions is not sufficient. We achieved greater success with the use of a warm-up model, in which warm-up from 10K to 30K occurs following a cold phase.
- ID:
- ivo://CDS.VizieR/J/A+A/607/A22
- Title:
- Monoceros R2 filament hub FIR observations
- Short Name:
- J/A+A/607/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present far-infrared observations of Monoceros R2 (a giant molecular cloud at approximately 830pc distance, containing several sites of active star formation), as observed at 70um, 160um, 250um, 350um, and 500um by the PACS and SPIRE instruments on the Herschel Space Observatory as part of the HOBYS Key programme. The Herschel data are complemented by SCUBA-2 data in the submillimetre range, and WISE and Spitzer data in the mid-infrared. In addition, C^18^O data from the IRAM 30-m Telescope are presented, and used for kinematic information. Sources were extracted from the maps with getsources, and from the fluxes measured, spectral energy distributions were constructed, allowing measurements of source mass and dust temperature. Of 177 Herschel sources robustly detected in the region (a detection with high signal-to-noise and low axis ratio at multiple wavelengths), including protostars and starless cores, 29 are found in a filamentary hub at the centre of the region (a little over 1% of the observed area). These objects are on average smaller, more massive, and more luminous than those in the surrounding regions (which together suggest that they are at a later stage of evolution), a result that cannot be explained entirely by selection effects. These results suggest a picture in which the hub may have begun star formation at a point significantly earlier than the outer regions, possibly forming as a result of feedback from earlier star formation. Furthermore, the hub may be sustaining its star formation by accreting material from the surrounding filaments.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A30
- Title:
- Monochromatic conversion factors to LIR & Mdust
- Short Name:
- J/A+A/609/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new, publicly available library of dust spectral energy distributions (SEDs). These SEDs are characterized by only three parameters: the dust mass (Mdust), the dust temperature (Tdust), and the mid-to-total infrared color (IR8=LIR/L8). The latter measures the relative contribution of polycyclic aromatic hydrocarbon (PAH) molecules to the total infrared luminosity. We used this library to model star-forming galaxies at 0.5<z<4 in the deep CANDELS fields, using both individual detections and stacks of Herschel and ALMA imaging, and extending this sample to z=0 using the Herschel Reference Survey. At first order, the dust SED of a galaxy was observed to be independent of stellar mass, but evolving with redshift. We found trends of increasing Tdust and IR8 with redshift and distance from the SFR-M* main sequence, and quantified for the first time their intrinsic scatter. Half of the observed variations of these parameters was captured by the above empirical relations, and after subtracting the measurement errors we found residual scatters of {delta}Tdust/Tdust=12% and {delta}logIR8=0.18dex. We observed second order variations with stellar mass: massive galaxies (M*>10^119M_{sun}_) at z<=1 have slightly lower temperatures indicative of a reduced star formation efficiency, while low mass galaxies (M*<10^10^M_{sun}_) at z>=1 showed reduced PAH emission, possibly linked to their lower metallicities. Building on these results, we constructed high-fidelity mock galaxy catalogs to predict the accuracy of infrared luminosities and dust masses determined using a single broadband measurement. Using a single James Webb Space Telescope (JWST) MIRI band, we found that LIR is typically uncertain by 0.15dex, with a maximum of 0.25dex when probing the rest-frame 8um, and this is not significantly impacted by typical redshift uncertainties. On the other hand, we found that ALMA bands 8 to 7 and 6 to 3 measured the dust mass at better than 0.2 and 0.15dex, respectively, and independently of redshift, while bands 9 to 6 only measured LIR at better than 0.2dex at z>1, 3.2, 3.8, and 5.7, respectively. Starburst galaxies had their LIR significantly underestimated when measured by a single JWST or ALMA band, while their dust mass from a single ALMA band were moderately overestimated. This dust library and the results of this paper can be used immediately to improve the design of observing proposals, and interpret more accurately the large amount of archival data from Spitzer, Herschel and ALMA.
- ID:
- ivo://CDS.VizieR/J/ApJ/784/111
- Title:
- Morphology of candidate intermediate-mass SFRs
- Short Name:
- J/ApJ/784/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an all-sky sample of 984 candidate intermediate-mass Galactic star-forming regions that are color selected from the Infrared Astronomical Satellite (IRAS) Point Source Catalog and morphologically classify each object using mid-infrared Wide-field Infrared Survey Explorer (WISE) images. Of the 984 candidates, 616 are probable star-forming regions (62.6%), 128 are filamentary structures (13.0%), 39 are point-like objects of unknown nature (4.0%), and 201 are galaxies (20.4%). We conduct a study of four of these regions, IRAS 00259+5625, IRAS 00420+5530, IRAS 01080+5717, and IRAS 05380+2020, at Galactic latitudes|b|>5{deg} using optical spectroscopy from the Wyoming Infrared Observatory, along with near-infrared photometry from the Two-Micron All Sky Survey, to investigate their stellar content. New optical spectra, color-magnitude diagrams, and color-color diagrams reveal their extinctions, spectrophotometric distances, and the presence of small stellar clusters containing 20-78M_{sun}_ of stars. These low-mass diffuse star clusters contain ~65-250 stars for a typical initial mass function, including one or more mid-B stars as their most massive constituents. Using infrared spectral energy distributions we identify young stellar objects near each region and assign probable masses and evolutionary stages to the protostars. The total infrared luminosity lies in the range 190-960L_{sun}_, consistent with the sum of the luminosities of the individually identified young stellar objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/652/1068
- Title:
- Morphology of cool and warm infrared galaxies
- Short Name:
- J/ApJ/652/1068
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed a sample of nearby cool and warm infrared (IR) galaxies using photometric and structural parameters. The set of measures include far-infrared color [C=log(S_60um_/S_100um_)], total IR luminosity (L_FIR_), radio surface brightness, and radio, near-infrared, and optical sizes.
