- ID:
- ivo://CDS.VizieR/J/ApJ/731/90
- Title:
- Mid-IR content of BGPS sources
- Short Name:
- J/ApJ/731/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for mid-infrared signs of star formation activity in the 1.1mm sources in the Bolocam Galactic Plane Survey (BGPS). We have correlated the BGPS catalog (Cat. J/ApJS/188/123) with available mid-IR Galactic plane catalogs based on the Spitzer Space Telescope GLIMPSE legacy survey (including Cat. J/AJ/136/2413 and the EGO cat. J/AJ/136/2391) and the Midcourse Space Experiment (MSX) Galactic plane survey (RMS catalog, Hoare et al. 2004ASPC..317..156H). We find that 44% (3712 of 8358) of the BGPS sources contain at least one mid-IR source, including 2457 of 5067 (49%) within the area where all surveys overlap (10{deg}<l<65{deg}). Accounting for chance alignments between the BGPS and mid-IR sources, we conservatively estimate that 20% of the BPGS sources within the area where all surveys overlap show signs of active star formation. We separate the BGPS sources into four groups based on their probability of star formation activity. Extended Green Objects and Red MSX Sources make up the highest probability group, while the lowest probability group is comprised of "starless" BGPS sources which were not matched to any mid-IR sources. The mean 1.1mm flux of each group increases with increasing probability of active star formation.
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- ID:
- ivo://CDS.VizieR/J/ApJ/831/124
- Title:
- Milky Way kinematics. II.
- Short Name:
- J/ApJ/831/124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using atomic hydrogen (HI) data from the VLA Galactic Plane Survey, we measure the HI terminal velocity as a function of longitude for the first quadrant of the Milky Way. We use these data, together with our previous work on the fourth Galactic quadrant, to produce a densely sampled, uniformly measured, rotation curve of the northern and southern Milky Way between 3kpc<R<8kpc. We determine a new joint rotation curve fit for the first and fourth quadrants, which is consistent with the fit we published in McClure-Griffiths & Dickey (Paper I, 2007ApJ...671..427M) and can be used for estimating kinematic distances interior to the solar circle. Structure in the rotation curves is now exquisitely well defined, showing significant velocity structure on lengths of ~200pc, which is much greater than the spatial resolution of the rotation curve. Furthermore, the shape of the rotation curves for the first and fourth quadrants, even after subtraction of a circular rotation fit shows a surprising degree of correlation with a roughly sinusoidal pattern between 4.2<R<7kpc.
- ID:
- ivo://CDS.VizieR/J/ApJ/834/57
- Title:
- Milky Way molecular clouds from ^12^CO
- Short Name:
- J/ApJ/834/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study presents a catalog of 8107 molecular clouds that covers the entire Galactic plane and includes 98% of the ^12^CO emission observed within b+/-5^{deg}^. The catalog was produced using a hierarchical cluster identification method applied to the result of a Gaussian decomposition of the Dame+ (2001ApJ...547..792D) data. The total H_2_ mass in the catalog is 1.2x10^9^M_{sun}_, in agreement with previous estimates. We find that 30% of the sight lines intersect only a single cloud, with another 25% intersecting only two clouds. The most probable cloud size is R~30pc. We find that M{propto}R^2.2+/-0.2^, with no correlation between the cloud surface density, {Sigma}, and R. In contrast with the general idea, we find a rather large range of values of {Sigma}, from 2 to 300M_{sun}_/pc^2^, and a systematic decrease with increasing Galactic radius, R_gal_. The cloud velocity dispersion and the normalization {sigma}_0_={sigma}_v_/R^1/2^ both decrease systematically with R_gal_. When studied over the whole Galactic disk, there is a large dispersion in the line width-size relation and a significantly better correlation between {sigma}_v_ and {Sigma}R. The normalization of this correlation is constant to better than a factor of two for R_gal_<20kpc. This relation is used to disentangle the ambiguity between near and far kinematic distances. We report a strong variation of the turbulent energy injection rate. In the outer Galaxy it may be maintained by accretion through the disk and/or onto the clouds, but neither source can drive the 100 times higher cloud-averaged injection rate in the inner Galaxy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/2222
- Title:
- 1.1mm dust continuum emission along Gal. plane
- Short Name:
- J/MNRAS/473/2222
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sensitive, imaging observations of the {lambda}1.1mm dust continuum emission from a 1deg^2^ area collected with the AzTEC bolometer camera on the Large Millimeter Telescope are presented. A catalogue of 1545 compact sources is constructed based on a Wiener-optimization filter. These sources are linked to larger clump structures identified in the Bolocam Galactic Plane Survey. Hydrogen column densities are calculated for all sources and mass and mean volume densities are derived for the subset of sources for which kinematic distances can be assigned. The AzTEC sources are localized, high-density peaks within the massive clumps of molecular clouds and comprise 5-15 per cent of the clump mass. We examine the role of the gravitational instability in generating these fragments by comparing the mass of embedded AzTEC sources to the Jeans mass of the parent BGPS object. For sources with distances less than 6kpc the fragment masses are comparable to the clump Jeans mass, despite having isothermal Mach numbers between 1.6 and 7.2. AzTEC sources linked to ultra compact HII regions have mass surface densities greater than the critical value implied by the mass-size relationship of infrared dark clouds with high-mass star formation, while AzTEC sources associated with Class II methanol masers have mass surface densities greater than 0.7gcm^-2^ that approaches the proposed threshold required to form massive stars.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A54
- Title:
- Molecular cloud assoc. to Milky Way spiral arms
- Short Name:
- J/A+A/658/A54
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The morphology of the Milky Way is still a matter of debate. In order to shed light on the uncertainty surrounding the Galactic structure, in this paper, we study the imprint of spiral arms on the molecular gas distribution and properties. To do so, we take full advantage of the SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic Interstellar Medium) survey that observed a large area of the inner Galaxy in the ^13^CO(2-1) line at an angular resolution of 28". We analyse the influences of spiral arms by considering the features of the molecular gas emission as a whole across the longitude- velocity map built from the full survey. Additionally, we examine the properties of the molecular clouds in the spiral arms compared to those in the inter-arm regions. Through flux and luminosity probability distribution functions, we find that the molecular gas emission associated with the spiral arms does not differ much from the emission between the arms. On average, spiral arms show masses per unit length of ~10^5^-10^6^M_{sun}_/kpc. This is similar to values inferred from data sets in which emission distributions were segmented into molecular clouds. By examining the cloud distribution across the Galactic plane, we infer that the molecular mass in the spiral arms is a factor of 1.5 higher than that of the inter-arm medium, similar to what is found for other spiral galaxies in the local Universe. We observe that only the distributions of cloud mass surface densities and aspect ratio in the spiral arms show significant differences compared to those of the inter-arm medium; other observed differences appear instead to be driven by a distance bias. By comparing our results with simulations and observations of nearby galaxies, we conclude that the measured quantities would classify the Milky Way as a flocculent spiral galaxy, rather than as a grand-design one.
- ID:
- ivo://CDS.VizieR/J/A+A/588/A104
- Title:
- Molecular clouds and star formation
- Short Name:
- J/A+A/588/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As a part of the Milky Way Imaging Scroll Painting (MWISP) survey, the aim is to study the physical properties of molecular clouds and their associated star formation toward the Galactic plane within 216.25{deg}<=l<=218.75{deg} and -0.75{deg}<=b<=1.25{deg}, which covers the molecular cloud complex S287. Using the 3x3 Superconducting Spectroscopic Array Receiver (SSAR) at the PMO-13.7m telescope, we performed a simultaneous ^12^CO (1-0), ^13^CO (1-0), C^18^O (1-0) mapping toward molecular clouds in a region encompassing 3.75 square degrees. The beam size is 52" for ^12^CO (1-0) and 55" for ^13^CO (1-0) and C^18^O (1-0).
- 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/A+A/552/A40
- Title:
- MSX high-contrast IRDCs with NH_3_
- Short Name:
- J/A+A/552/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Despite increasing research in massive star formation, little is known about its earliest stages. Infrared Dark Clouds (IRDCs) are cold, dense and massive enough to harbour the sites of future high-mass star formation. But up to now, mainly small samples have been observed and analysed. To understand the physical conditions during the early stages of high-mass star formation, it is necessary to learn more about the physical conditions and stability in relatively unevolved IRDCs. Thus, for characterising IRDCs studies of large samples are needed. We investigate a complete sample of 220 northern hemisphere high-contrast IRDCs using the ammonia (1,1)- and (2,2)-inversion transitions. We detected ammonia (1,1)-inversion transition lines in 109 of our IRDC candidates. Using the data we were able to study the physical conditions within the star-forming regions statistically. We compared them with the conditions in more evolved regions which have been observed in the same fashion as our sample sources. Our results show that IRDCs have, on average, rotation temperatures of 15K, are turbulent (with line width FWHMs around 2km/s), have ammonia column densities on the order of 10^14^cm^-2^ and molecular hydrogen column densities on the order of 10^22^cm^-2^. Their virial masses are between 100 and a few 1000M_{sun}_. The comparison of bulk kinetic and potential energies indicate that the sources are close to virial equilibrium. IRDCs are on average cooler and less turbulent than a comparison sample of high-mass protostellar objects, and have lower ammonia column densities. Virial parameters indicate that the majority of IRDCs are currently stable, but are expected to collapse in the future.
- ID:
- ivo://CDS.VizieR/J/ApJS/248/24
- Title:
- MUSTANG-2 Galactic Plane survey at 3mm (MGPS90)
- Short Name:
- J/ApJS/248/24
- Date:
- 04 Dec 2021
- Publisher:
- CDS
- Description:
- We report the results of a pilot program for a Green Bank Telescope MUSTANG-2 Galactic Plane survey at 3mm (90GHz), MGPS90. The survey achieves a typical 1{sigma} depth of 1-2mJy/beam with a 9" beam. We describe the survey parameters, quality assessment process, cataloging, and comparison with other data sets. We have identified 709 sources over seven observed fields selecting some of the most prominent millimeter-bright regions between 0{deg}<l<50{deg} (total area ~7.5deg^2^). The majority of these sources have counterparts at other wavelengths. By applying flux selection criteria to these sources, we successfully recovered several known hypercompact HII (HCHII) regions but did not confirm any new ones. We identify 126 sources that have mm-wavelength counterparts but do not have cm-wavelength counterparts and are therefore candidate HCHII regions; of these, 10 are morphologically compact and are strong candidates for new HCHII regions. Given the limited number of candidates in the extended area in this survey compared to the relatively large numbers seen in protoclusters W51 and W49, it appears that most HCHII regions exist within dense protoclusters. Comparing the counts of HCHII to ultracompact HII (UCHII) regions, we infer the HCHII region lifetime is 16%-46% that of the UCHII region lifetime. We additionally separated the 3mm emission into dust and free-free emission by comparing with archival 870{mu}m and 20cm data. In the selected pilot fields, most (>~80%) of the 3mm emission comes from plasma, either through free-free or synchrotron emission.
- ID:
- ivo://CDS.VizieR/VIII/82
- Title:
- 2nd Epoch Molonglo Galactic Plane Survey (MGPS-2)
- Short Name:
- VIII/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The MGPS-2 (second epoch Molonglo Galactic Plane Survey) was carried out with the Molonglo Observatory Synthesis Telescope at a frequency of 843MHz and with a restoring beam of 45"x45"csd|{delta}|, making it he highest resolution large scale radio survey of the southern Galactic plane. It covers the range |b|<10{deg} and 245<l<365{deg}; it is the Galactic counterpart to the SUMSS (Cat. VIII/81) which covers the southern sky ({delta}<-30{deg}, |b|>10{deg}). This catalogue (15-Aug-2007) consists of 48850 compact sources, made by fitting elliptical gaussians in the MGPS-2 mosaics to a limiting peak brightness of 10mJy/beam. We used a custom method (described in the associated publication) to remove extended sources from the catalogue. Positions in the catalogue are accurate to 1-2". See http://www.astrop.physics.usyd.edu.au/mosaics for access to the mosaic images.
