- ID:
- ivo://CDS.VizieR/J/MNRAS/416/178
- Title:
- 1.2-mm dust clumps with luminous water masers
- Short Name:
- J/MNRAS/416/178
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a sensitive water maser search with the Australia Telescope Compact Array towards 267 1.2-mm dust clumps presented in the literature. We combine our new observations with previous water maser observations to extend our sample to 294 1.2-mm dust clumps, towards which we detect 165 distinct water maser sites towards 128 1.2-mm dust clumps. Within the fields of our observations, we additionally find four water masers with no apparent associated 1.2-mm dust continuum emission. Our overall detection rate of 44 per cent appears to vary as a function of Galactic longitude. We find that there is an excellent correspondence between the locations of the detected water masers with the peak of the target 1.2-mm dust clump sources. As expected from previous similar studies, the water masers are chiefly detected towards the bigger, brighter and more massive 1.2-mm dust clumps.
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Search Results
- 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/426/119
- Title:
- 1.2mm mapping of RCW 106 Giant Molecular Cloud
- Short Name:
- J/A+A/426/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have mapped the dust continuum emission from the molecular cloud covering a region of 28pcx94pc associated with the well-known H II region RCW 106 at 1.2mm using SIMBA on SEST. The observations, having an HPBW of 24" (0.4pc), reveal 95 clumps, of which about 50% have MSX associations and only 20% have IRAS associations. Owing to their higher sensitivity to colder dust and higher angular resolution the present observations identify new emission features and also show that most of the IRAS sources in this region consist of multiple dust emission peaks. The detected millimeter sources (MMS) include on one end the exotic MMS5 (associated with IRAS 16183-4958, one of the brightest infrared sources in our Galaxy) and the bright (and presumably cold) source MMS54, with no IRAS or MSX associations on the other end. Around 10% of the sources are associated with signposts of high mass star formation activity.
- ID:
- ivo://CDS.VizieR/J/A+A/499/149
- Title:
- 1.2mm maps of southern Infrared Dark Clouds
- Short Name:
- J/A+A/499/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- What are the mechanisms by which massive stars form? What are the initial conditions for these processes? It is commonly assumed that cold and dense Infrared Dark Clouds (IRDCs) likely represent the birth sites massive stars. Therefore, this class of objects gets increasing attention, and their analysis offers the opportunity to tackle the above mentioned questions. To enlarge the sample of well-characterised IRDCs in the southern hemisphere, where ALMA will play a major role in the near future, we have set up a program to study the gas and dust of southern infrared dark clouds. The present paper aims at characterizing the continuum properties of this sample of IRDCs. We cross-correlated 1.2 mm continuum data from SIMBA@SEST with Spitzer/GLIMPSE images to establish the connection between emission sources at millimeter wavelengths a nd the IRDCs we see at 8{mu}m in absorption against the bright PAH background. Analysing the dust emission and extinction leads to a determination of masses and column densities, which are important quantities in characterizing the initial conditions of massive star formation. We also evaluated the limitations of the emission and extinction methods. The morphology of the 1.2mm continuum emission is in all cases in close agreement with the mid-infrared extinction. The total masses of the IRDCs were found to range from 150 to 1150M_{sun}_ (emission data) and from 300 to 1750M_{sun}_ (extinction data). We derived peak column densities between 0.9 and 4.6x10^22^cm^-2^ (emission data) and 2.1 and 5.4x10^22^cm^-2^ (extinction data). We demonstrate that the extinction method fails for very high extinction values (and column densities) beyond A_V_ values of roughly 75mag according to the Weingartner & Draine (2001ApJ...548..296W) extinction relation R_V_=5.5 model B (around 200mag when following the common Mathis (1990ARA&A..28...37M) extinction calibration). By taking the spatial resolution effects into account and restoring the column densities derived from the dust emission back to a linear resolution of 0.01pc, peak column densities of 3.0x10^23^cm^-2^ are obtained, much higher than typic al values for low-mass cores. The derived column densities, taking into account the spatial resolution effects, are beyond the column density threshold of 3.0x10^23^cm^-2^ required by theoretical considerations for massive star formation. We conclude that the values for column densities derived for the selected IRDC sample make these objects excellent candidates for objects in the earliest stages of massive star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/579/A101
- Title:
- 3mm molecular line survey of 8 AGN
- Short Name:
- J/A+A/579/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim for a better understanding of the imprints that the nuclear activity in galaxies leaves in the molecular gas. We used the IRAM 30m telescope to observe the frequency range ~[86-116]GHz towards the central regions of the star- burst galaxies M83, M82, and NGC253, the galaxies hosting an active galactic nucleus (AGN) M51, NGC1068, and NGC7469, and the ultra-luminous infrared galaxies (ULIRGs) Arp220 and Mrk231. Assuming local thermodynamic equilibrium (LTE), we calculated the column densities of 27 molecules and 10 isotopologues (or their upper limits in case of non-detections).
- ID:
- ivo://CDS.VizieR/J/A+A/613/A42
- Title:
- M-3.8+0.9 molecular cloud 3mm datacubes
- Short Name:
- J/A+A/613/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to reveal the morphology, chemical composition, kinematics and to establish the main processes prevalent in the gas at the footpoints of the giant molecular loops (GMLs) in the Galactic center region. Using the 22-m Mopra telescope, we mapped the M-3.8+0.9 molecular cloud, placed at the footpoints of a giant molecular loop, in 3-mm range molecular lines. To derive the molecular hydrogen column density, we also observed the ^13^CO (2-1) line at 1mm using the 12-m APEX telescope. From the 3 mm observations 12 molecular species were detected, namely HCO+, HCN, H^13^CN, HNC, SiO, CS, CH_3_OH, N_2_H^+^, SO, HNCO, OCS, and HC_3_N. Maps revealing the morphology and kinematics of the M-3.8+0.9 molecular cloud in different molecules are presented. We identify six main molecular complexes. We derive fractional abundances in 11 selected positions of the different molecules assuming local thermodynamical equilibrium. Most of the fractional abundances derived for the M-3.8+0.9 molecular cloud are very similar over the whole cloud. However, the fractional abundances of some molecules show significant difference with respect to those measured in the central molecular zone (CMZ). The abundances of the shock tracer SiO are very similar between the GMLs and the CMZ. The methanol emission is the most abundant species in the GMLs. This indicates that the gas is likely affected by moderate ~30km/s or even high velocity (50km/s) shocks, consistent with the line profile observed toward one of the studied position. The origin of the shocks is likely related to the flow of the gas throughout the GMLs towards the footpoints.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A146
- Title:
- M33 molecular clouds and young stellar clusters
- Short Name:
- J/A+A/601/A146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the association between giant molecular clouds (GMCs) and young stellar cluster candidates (YSCCs) to shed light on the time evolution of local star formation episodes in the nearby galaxy M33. The CO (J=2-1) IRAM all-disk survey was used to identify and classify 566 GMCs with masses between 2x10^4^ and 2x10^6^M_{sun}_ across the whole star-forming disk of M33. In the same area, there are 630 YSCCs that we identified using Spitzer-24um data. Some YSCCs are embedded star-forming sites, while the majority have GALEX-UV and H{alpha} counterparts with estimated cluster masses and ages. The GMC classes correspond to different cloud evolutionary stages: inactive clouds are 32% of the total and classified clouds with embedded and exposed star formation are 16% and 52% of the total, respectively. Across the regular southern spiral arm, inactive clouds are preferentially located in the inner part of the arm, possibly suggesting a triggering of star formation as the cloud crosses the arm. The spatial correlation between YSCCs and GMCs is extremely strong, with a typical separation of 17pc. This is less than half the CO (2-1) beam size and illustrates the remarkable physical link between the two populations. GMCs and YSCCs follow the HI filaments, except in the outermost regions, where the survey finds fewer GMCs than YSCCs, which is most likely due to undetected clouds with low CO luminosity. The distribution of the non-embedded YSCC ages peaks around 5Myr, with only a few being as old as 8-10Myr. These age estimates together with the number of GMCs in the various evolutionary stages lead us to conclude that 14Myr is the typical lifetime of a GMC in M33 prior to cloud dispersal. The inactive and embedded phases are short, lasting about 4 and 2Myr, respectively. This underlines that embedded YSCCs rapidly break out from the clouds and become partially visible in H{alpha} or UV long before cloud dispersal.
- ID:
- ivo://CDS.VizieR/J/ApJ/853/171
- Title:
- mm point sources in the extended Sgr B2 cloud
- Short Name:
- J/ApJ/853/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report ALMA observations with resolution ~0.5" at 3mm of the extended Sgr B2 cloud in the Central Molecular Zone (CMZ). We detect 271 compact sources, most of which are smaller than 5000au. By ruling out alternative possibilities, we conclude that these sources consist of a mix of hypercompact HII regions and young stellar objects (YSOs). Most of the newly detected sources are YSOs with gas envelopes that, based on their luminosities, must contain objects with stellar masses M*>~8M_{sun}_. Their spatial distribution spread over a ~12x3pc region demonstrates that Sgr B2 is experiencing an extended star formation event, not just an isolated "starburst" within the protocluster regions. Using this new sample, we examine star formation thresholds and surface density relations in Sgr B2. While all of the YSOs reside in regions of high column density (N(H_2_)>~2x10^23^cm^-2^), not all regions of high column density contain YSOs. The observed column density threshold for star formation is substantially higher than that in solar vicinity clouds, implying either that high-mass star formation requires a higher column density or that any star formation threshold in the CMZ must be higher than in nearby clouds. The relation between the surface density of gas and stars is incompatible with extrapolations from local clouds, and instead stellar densities in Sgr B2 follow a linear {Sigma}_*_-{Sigma}_gas_ relation, shallower than that observed in local clouds. Together, these points suggest that a higher volume density threshold is required to explain star formation in CMZ clouds.
- ID:
- ivo://CDS.VizieR/J/ApJ/638/293
- Title:
- 1.1mm sources in the Perseus Molecular Cloud
- Short Name:
- J/ApJ/638/293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have completed a 1.1mm continuum survey of 7.5{deg}^2^ of the Perseus Molecular Cloud using Bolocam at the Caltech Submillimeter Observatory. This represents the largest millimeter or submillimeter continuum map of Perseus to date. Our map covers more than 30,000 31" (FWHM) resolution elements to a 1{sigma} rms of 15mJy/beam. We detect a total of 122 cores above a 5{sigma} point-source mass detection limit of 0.18M_{sun}_, assuming a dust temperature of T_D_=10K, 60 of which are new millimeter or submillimeter detections.
- ID:
- ivo://CDS.VizieR/J/ApJ/705/144
- Title:
- Molecular and atomic gas in the LMC. II.
- Short Name:
- J/ApJ/705/144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare the CO (J=1-0) and HI emission in the Large Magellanic Cloud in three dimensions, i.e., including a velocity axis in addition to the two spatial axes, with the aim of elucidating the physical connection between giant molecular clouds (GMCs) and their surrounding HI gas. The CO(J=1-0) data set is from the second NANTEN CO survey (Fukui et al. 2008, Cat. J/ApJS/178/56) and the HI data set is from the merged Australia Telescope Compact Array (ATCA) and Parkes Telescope surveys (Kim et al. 2003ApJS..148..473K).
