- ID:
- ivo://CDS.VizieR/J/ApJ/761/37
- Title:
- CO observations in giant molecular clouds of M33
- Short Name:
- J/ApJ/761/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a giant molecular cloud (GMC) catalog of M33 (NGC598), containing 71 GMCs in total, based on wide-field and high-sensitivity CO(J=3-2) observations with a spatial resolution of 100pc using the ASTE 10m telescope. Employing archival optical data, we identify 75 young stellar groups (YSGs) from the excess of the surface stellar density, and estimate their ages by comparing with stellar evolution models. A spatial comparison among the GMCs, YSGs, and H II regions enable us to classify GMCs into four categories: Type A, showing no sign of massive star formation (SF); Type B, being associated only with H II regions; Type C, with both H II regions and <10Myr old YSGs; and Type D, with both H II regions and 10-30Myr YSGs. Out of 65 GMCs (discarding those at the edges of the observed fields), 1 (1%), 13 (20%), 29 (45%), and 22 (34%) are Types A, B, C, and D, respectively. We interpret these categories as stages in a GMC evolutionary sequence. Assuming that the timescale for each evolutionary stage is proportional to the number of GMCs, the lifetime of a GMC with a mass >10^5^M_{sun}_ is estimated to be 20-40Myr. In addition, we find that the dense gas fraction as traced by the CO(J=3-2)/CO(J=1-0) ratio is enhanced around SF regions. This confirms a scenario where dense gas is preferentially formed around previously generated stars, and will be the fuel for the next stellar generation. In this way, massive SF gradually propagates in a GMC until gas is exhausted.
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- ID:
- ivo://CDS.VizieR/J/ApJS/178/302
- Title:
- C^18^O observations of multiple-core systems
- Short Name:
- J/ApJS/178/302
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of C^18^O observations by the Nobeyama Millimeter Array toward dense clumps with radii of ~0.3pc in six cluster-forming regions including massive (proto) stars. We identified 171 cores, whose radius, line width, and molecular mass range from 0.01 to 0.09pc, 0.43 to 3.33km/s, and 0.5 to 54.1M_{sun}_, respectively. Many cores with various line widths exist in one clump, and the index of the line width-radius relationship of the cores and the parental clump differs from core to core in the clump. This indicates that the degree of dissipation of the turbulent motion varies for each core in one clump.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/29
- Title:
- CO obs. of Planck Galactic cold clumps
- Short Name:
- J/ApJS/247/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sixty-five Planck Galactic cold clumps (PGCCs) from the first quadrant (IQuad) and 39 from the anticenter direction region (ACent) were observed in ^12^CO, ^13^CO, and C^18^O J=1-0 lines using the 13.7m telescope of the Purple Mountain Observatory. All the targets were detected in all three lines, except for 12 IQuad and 8 ACent PGCCs without C^18^O detection. Seventy-six and 49 velocity components were obtained in IQuad and ACent respectively; 146 cores were extracted from 76 IQuad clumps and 100 cores from 49 ACent clumps. The average Tex of IQuad cores and ACent cores is 12.4K and 12.1K, respectively. The average line widths of ^13^CO of IQuad cores and ACent cores are 1.55km/s and 1.77km/s, respectively. Among the detected cores, 24 in IQuad and 13 in ACent have asymmetric line profiles. The small blue excesses, ~0.03 in IQuad and 0.01 in ACent, indicate that star formation is not active in these PGCC cores. Power-law fittings of the core mass function to the high-mass end give indices of -0.57 in IQuad and -1.02 in ACent, which are flatter than the slope of the initial mass function given by Salpeter. The large turnover masses of 28M_{sun}_ for IQuad cores and 77M_{sun}_ for ACent cores suggest low star formation efficiencies in PGCCs. The correlation between virial mass and gas mass indicates that most PGCC cores in both regions are not likely pressure-confined.
- ID:
- ivo://CDS.VizieR/J/ApJ/862/105
- Title:
- Core mass function across Gal. env. II. IRDC clumps
- Short Name:
- J/ApJ/862/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the core mass function (CMF) within 32 dense clumps in seven infrared dark clouds (IRDCs) with the Atacama Large Millimeter/submillimeter Array via 1.3mm continuum emission at a resolution of ~1". We have identified 107 cores with the dendrogram algorithm, with a median radius of about 0.02pc. Their masses range from 0.261 to 178M_{sun}_. After applying completeness corrections, we fit the combined IRDC CMF with a power law of the form dN/d.logM{propto}M^-{alpha}^ and derive an index of {alpha}~0.86+/-0.11 for M>=0.79M_{sun}_ and {alpha}~0.70+/-0.13 for M>=1.26M_{sun}_, which is a significantly more top-heavy distribution than the Salpeter stellar initial mass function index of 1.35. We also make a direct comparison of these IRDC clump CMF results to those measured in the more evolved protocluster G286 derived with similar methods, which have {alpha}~1.29+/-0.19 and 1.08+/-0.27 in these mass ranges, respectively. These results provide a hint that, especially for the M>=1.26M_{sun}_ range where completeness corrections are modest, the CMF in high pressure, early-stage environments of IRDC clumps may be top-heavy compared to that in the more evolved, global environment of the G286 protoclusters. However, larger samples of cores probing these different environments are needed to better establish the robustness of this potential CMF variation.
- ID:
- ivo://CDS.VizieR/J/A+A/611/A99
- Title:
- Cores in HII regions parameters
- Short Name:
- J/A+A/611/A99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-mass stars form in much richer environments than those associated with isolated low-mass stars, and once they reach a certain mass, produce ionised (HII) regions. The formation of these pockets of ionised gas are unique to the formation of high-mass stars (M>8M_{sun}_), and present an excellent opportunity to study the final stages of accretion, which could include accretion through the HII region itself. This study of the dynamics of the gas on both sides of these ionisation boundaries in very young HII regions aims to quantify the relationship between the HII regions and their immediate environments. We present high-resolution (~0.5") ALMA observations of nine HII regions selected from the Red MSX Source (RMS, Lumsden et al., Cat. J/ApJS/208/11) survey with compact radio emission and bolometric luminosities greater than 10^4^L_{sun}_. We focus on the initial presentation of the data, including initial results from the radio recombination line H29{alpha} some complementary molecules, and the 256GHz continuum emission.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A11
- Title:
- Corona Australis ALMA and X-Shooter data
- Short Name:
- J/A+A/626/A11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years, the disk populations in a number of young star-forming regions have been surveyed with the Atacama Large Millimeter/submillimeter Array (ALMA). Understanding the disk properties and their correlation with the properties of the central star is critical to understanding planet formation. In particular, a decrease of the average measured disk dust mass with the age of the region has been observed, consistent with grain growth and disk dissipation. We aim to compare the general properties of disks and their host stars in the nearby (d=160pc) Corona Australis (CrA) star forming region to those of the disks and stars in other regions. We conducted high-sensitivity continuum ALMA observations of 43 Class II young stellar objects in CrA at 1.3mm (230GHz). The typical spatial resolution is 0.3''. The continuum fluxes ar e used to estimate the dust masses of the disks, and a survival analysis is performed to estimate the average dust mass. We also obtained new VLT/X-Shooter spectra for 12 of the objects in our sample for which spectral type (SpT) information was missing. Twenty-four disks were detected, and stringent limits have been put on the average dust mass of the nondetections. Taking into account the upper limits, the average disk mass in CrA is 6+/-3M_{sun}_. This value is significantly lower than that of disks in other young (1-3Myr) star forming regions (Lupus, Taurus, Chamaeleon I, and Ophiuchus) and appears to be consistent with the average disk mass of the 5-10Myr-old Upper Sco. The position of the stars in our sample on the Herzsprung-Russel diagram however seems to confirm that CrA has an age similar to Lupus. Neither external photoevaporation nor a lower-than-usual stellar mass distribution can explain the low disk masses. On the other hand, a low-mass disk population could be explained if the disks were small, which could happen if the parent cloud had a low temperature or intrinsic angular momentum, or if the angular momentum of the cloud were removed by some physical mechanism such as magnetic braking. Even in detected disks, none show clear substructures or cavities. Our results suggest that in order to fully explain and understand the dust mass distribution of protoplanetary disks and their evolution, it may also be necessary to take into consideration the initial conditions of star- and disk-formation process. These conditions at the very beginning may potentially vary from region to region, and could play a crucial role in planet formation and evolution.
- ID:
- ivo://CDS.VizieR/J/ApJS/196/18
- Title:
- CO survey of galactic molecular clouds. II.
- Short Name:
- J/ApJS/196/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present fully sampled 38" resolution maps of the CO and ^13^CO J=2-1 lines in the molecular clouds toward the HII region complex W3. The maps cover a 2.0{deg}x1.67{deg} section of the galactic plane and span -70 to -20km/s (LSR) in velocity with a resolution of ~1.3km/s. The velocity range of the images includes all the gas in the Perseus spiral arm. We also present maps of CO J=3-2 emission for a 0.5{deg}x0.33{deg} area containing the HII regions W3 Main and W3(OH). The J=3-2 maps have velocity resolution of 0.87km/s and 24" angular resolution. Color figures display the peak line brightness temperature, the velocity-integrated intensity, and velocity channel maps for all three lines, and also the (CO/^13^CO) J=2-1 line intensity ratios as a function of velocity. The line intensity image cubes are made available in standard FITS format as electronically readable files. We compare our molecular line maps with the 1.1mm continuum image from the BOLOCAM Galactic Plane Survey (BGPS). From our ^13^CO image cube, we derive kinematic information for the 65 BGPS sources in the mapped field, in the form of Gaussian component fits.
- ID:
- ivo://CDS.VizieR/J/ApJS/191/232
- Title:
- CO survey of W51 molecular cloud
- Short Name:
- J/ApJS/191/232
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 38" resolution maps of the CO and ^13^COJ=2-1 lines in the molecular clouds toward the HII region complex W51. The maps cover a 1.25x1{deg} section of the galactic plane and span +30 to +85km/s (LSR) in velocity. The spectral resolution is ~1.3km/s. The velocity range of the images includes all the gas in the Sagittarius spiral arm. Color figures display the peak line brightness temperature, the velocity-integrated intensity, and 2km/s channel-averaged maps for both isotopologs, and also the CO/^13^COJ=2-1 line intensity ratio as a function of velocity. The CO and ^13^CO line intensity image cubes are made available in standard FITS format as electronically readable tables. We compare our molecular line maps with the 1.1mm continuum image from the BOLOCAM Galactic Plane Survey (BGPS; Aguirre et al. 2011ApJS..192....4A; Rosolowsky et al. 2010, Cat. J/ApJS/188/123). From our ^13^CO image cube, we derive kinematic information for the 99 BGPS sources in the mapped field in the form of Gaussian component fits. The integrated ^13^CO line intensity and the 1.1mm source flux density show only a modest degree of correlation for the 99 sources, likely due to a range of dust and gas physical conditions within the sources. However, the 1.1mm continuum surface brightness and the integrated ^13^CO line intensity for small regions containing single BGPS sources and molecular clouds show very good correlations in many cases.
- ID:
- ivo://CDS.VizieR/J/ApJ/850/83
- Title:
- DANCING-ALMA. I. submm/mm continuum sources
- Short Name:
- J/ApJ/850/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the large statistics of the galaxy effective radius Re in the rest-frame far-infrared (FIR) wavelength R_e(FIR)_ obtained from 1627 Atacama Large Millimeter/submillimeter Array (ALMA) 1mm band maps that become public by 2017 July. Our ALMA sample consists of 1034 sources with the star formation rate ~100-1000M_{sun}_/yr and the stellar mass ~10^10^-10^11.5^M_{sun}_ at z=0-6. We homogeneously derive R_e(FIR)_ and FIR luminosity LFIR of our ALMA sources via the uv-visibility method with the exponential disk model, carefully evaluating selection and measurement incompletenesses by realistic Monte-Carlo simulations. We find that there is a positive correlation between R_e(FIR)_ and LFIR at the >99% significance level. The best-fit power-law function, R_e(FIR)_{propto}L_FIR_^{alpha}^, provides {alpha}=0.28+/-0.07, and shows that R_e(FIR)_ at a fixed LFIR decreases toward high redshifts. The best-fit {alpha} and the redshift evolution of R_e(FIR)_ are similar to those of Re in the rest-frame UV (optical) wavelength R_e(UV)_ (R_e(Opt)_) revealed by Hubble Space Telescope (HST) studies. We identify that our ALMA sources have significant trends of R_e(FIR)_<~R_e(UV)_ and R_e(Opt)_, which suggests that the dusty starbursts take place in compact regions. Moreover, R_e(FIR)_ of our ALMA sources is comparable to R_e(Opt)_ of quiescent galaxies at z~1-3 as a function of stellar mass, supporting the evolutionary connection between these two galaxy populations. We also investigate rest- frame UV and optical morphologies of our ALMA sources with deep HST images, and find that ~30%-40% of our ALMA sources are classified as major mergers. This indicates that dusty starbursts are triggered by not only the major mergers but also the other mechanism(s).
- ID:
- ivo://CDS.VizieR/J/A+A/593/A51
- Title:
- Debris discs around nearby FGK stars
- Short Name:
- J/A+A/593/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Debris discs are a consequence of the planet formation process and constitute the fingerprints of planetesimal systems. Their counterparts in the solar system are the asteroid and Edgeworth-Kuiper belts. The aim of this paper is to provide robust numbers for the incidence of debris discs around FGK stars in the solar neighbourhood. The full sample of 177 FGK stars with d>=20pc proposed for the DUst around NEarby Stars (DUNES) survey is presented. Herschel/PACS observations at 100 and 160{mu}m were obtained, and were complemented in some cases with data at 70{mu}m and at 250, 350, and 500{mu}m SPIRE photometry. The 123 objects observed by the DUNES collaboration were presented in a previous paper. The remaining 54 stars, shared with the Disc Emission via a Bias-free Reconnaissance in IR and Sub-mm (DEBRIS) consortium and observed by them, and the combined full sample are studied in this paper. The incidence of debris discs per spectral type is analysed and put into context together with other parameters of the sample, like metallicity, rotation and activity, and age. The subsample of 105 stars with d>=15pc containing 23 F, 33 G, and 49 K stars is complete for F stars, almost complete for G stars, and contains a substantial number of K stars from which we draw solid conclusions on objects of this spectral type. The incidence rates of debris discs per spectral type are 0.26^+0.21^_-0.14_ (6 objects with excesses out of 23 F stars), 0.21^+0.17^_-0.11_ (7 out of 33 G stars), and 0.20^0.14^_-0.09_ (10 out of 49 K stars); the fraction for all three spectral types together is 0.22^+0.08^_-0.07_ (23 out of 105 stars). The uncertainties correspond to a 95% confidence level. The medians of the upper limits of L_dust_/L* for each spectral type are 7.8x10^-7^ (F), 1.4x10^-6^ (G), and 2.2x10^-6^ (K); the lowest values are around 4.0x10^-7^. The incidence of debris discs is similar for active (young) and inactive (old) stars. The fractional luminosity tends to drop with increasing age, as expected from collisional erosion of the debris belts.
