- ID:
- ivo://CDS.VizieR/J/A+A/545/A51
- Title:
- 1.4mm and 3mm interferometry of IRAS 19410+2336
- Short Name:
- J/A+A/545/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The core mass functions (CMFs) of low-mass star-forming regions are found to resemble the shape of the initial mass function (IMF). A similar result is observed for the dust clumps in high-mass star-forming regions, although on spatial scales of clusters that do not resolve the substructure that is found in these massive clumps. The region IRAS 19410+2336 is one exception, having been observed on spatial scales on the order of ~2500AU, which are sufficient to resolve the clump substructure into individual cores. We investigate the protostellar content of IRAS 19410+2336 at high spatial resolution at 1.4mm, determining the temperature structure of the region and deriving its CMF. The massive star-forming region IRAS 19410+2336 was mapped with the PdBI (BCD configurations) at 1.4mm and 3mm in the continuum and several transitions of formaldehyde (H_2_CO) and methyl cyanide (CH_3_CN). The H_2_CO transitions were also observed with the IRAM 30m Telescope. We detect 26 continuum sources at 1.4mm with a spatial resolution as low as ~2200AU, several of them with counterparts at near-infrared and mid-infrared wavelengths, distributed in two (proto)clusters. With the PdBI CH_3_CN and PdBI/IRAM 30m H_2_CO emission, we derive the temperature structure of the region, ranging from 35K to 90K. Using these temperatures, we calculate the core masses of the detected sources, ranging from ~0.7M_{sun}_ to ~8M_{sun}_. These masses are strongly affected by the spatial filtering of the interferometer, which removes a common envelope with ~90% of the single- dish flux. Considering only the detected dense cores and accounting for binning effects as well as cumulative distributions, we derive a CMF, with a power-law index b=~2.3+/-0.2. We resolve the Jeans length of the (proto)clusters by one order of magnitude, and only find a small velocity dispersion between the different subsources. Since we cannot unambiguously differentiate between protostellar and prestellar cores, the derived CMF is not prestellar. Furthermore, because of the large fraction of missing flux, we cannot establish a firm link between the CMF and the IMF. This implies that future high-mass CMF studies will need to complement the interferometer continuum data with the short spacing information, a task suitable for ALMA. We note that the method of extracting temperatures using H_2_CO lines becomes less applicable when reaching the dense core scales of the interferometric observations because most of the H_2_CO appears to originate in the envelope structure.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/568/A56
- Title:
- mm continuum and line images of G0.253+0.016
- Short Name:
- J/A+A/568/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The massive infrared dark cloud G0.253+0.016 projected ~45pc from the Galactic centre contains ~10^5^M_{sun}_ of dense gas whilst being mostly devoid of observed star-formation tracers. Our goals are therefore to scrutinise the physical properties, dynamics and structure of this cloud with reference to its star-forming potential. We have carried out a concerted SMA and IRAM 30m study of this enigmatic cloud in dust continuum, CO isotopologues, several shock tracing molecules, as well as H_2_CO to trace the gas temperature. In addition, we include ancillary far-IR and sub-mm Herschel and SCUBA data in our analysis. We detect and characterise a total of 36 dust cores within G0.253+0.016 at 1.3mm and 1.37mm, with masses between 25 and approximately 250M_{sun}_, and find that the kinetic temperature of the gas traced by H_2_CO ratios is >320K on size-scales of ~0.15pc. Analysis of the position-velocity diagrams of our observed lines show broad linewidths and strong shock emission in the south of the cloud, indicating that G0.253+0.016 is colliding with another cloud at v_LSR_~70km/s. We confirm via an analysis of the observed dynamics in the Central Molecular Zone that it is an elongated structure, orientated with Sgr B2 closer to the Sun than Sgr A*, however our results suggest that the actual geometry may be more complex than an elliptical ring. We find that the column density Probability Distribution Function (PDF) of G0.253+0.016 derived from SMA and SCUBA dust continuum emission is log-normal with no discernible power-law tail, consistent with little star formation, and that its width can be explained in the framework of theory predicting the density structure of clouds created by supersonic, magnetised turbulence. We also present the Delta-variance spectrum of this region, a proxy for the density power spectrum of the cloud, and show it is consistent with that expected for clouds with no current star formation. Finally, we show that even after determining a scaled column density threshold for star formation by incorporating the effects of the increased turbulence in the cloud, we would still expect ten stars with masses >15M_{sun}_ to form in G0.253+0.016. If these cannot be accounted for by new radio continuum observations, then further physical aspects may be important, such as the background column density level, which would turn an absolute column density threshold for star formation into a critical over-density. We conclude that G0.253+0.016 contains high-temperatures and wide-spread shocks, displaying evidence of interaction with a nearby cloud which we identify at v_LSR_~70km/s. Our analysis of the structure of the cloud can be well-explained by theory of magnetised turbulence, and is consistent with little or no current star formation. Using G0.253+0.016 as a test-bed of the conditions required for star formation in a different physical environment to that of nearby clouds, we also conclude that there is not one column density threshold for star formation, but instead this value is dependant on the local physical conditions.
- 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/411/1367
- Title:
- 12mm line survey towards W28 SNR
- Short Name:
- J/MNRAS/411/1367
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 12mm Mopra observations of dense molecular gas towards the W28 supernova remnant (SNR) field. The focus is on the dense molecular gas towards the TeV gamma-ray sources detected by the HESS telescopes, which likely trace the cosmic rays from W28 and possibly other sources in the region. Using the NH_3_ inversion transitions we reveal several dense cores inside the molecular clouds,
- 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+AS/142/181
- Title:
- 2mm molecular line survey of IRC+10 216
- Short Name:
- J/A+AS/142/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mm-wave spectrum of the C-star envelope IRC+10 216 has been continuously surveyed between 129.0 and 172.5GHz with the IRAM 30-m telescope. 380 lines are detected, of which 317 have been identified. The identified lines arise from 30 different molecules and radicals which, in their vast majority, are not observed in hot and dense interstellar clouds such as Orion A or W3(OH). Actually, half of the molecular species identified in the mm-wave spectrum of IRC+10216 were first observed in the course of this spectral survey.
- ID:
- ivo://CDS.VizieR/J/A+AS/122/271
- Title:
- mm-monitoring of radio sources IV.
- Short Name:
- J/A+AS/122/271
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radio flux densities are presented for 118 extragalactic radio sources monitored at 90, 142 and 230GHz with the IRAM 30m telescope during 1993-1994. For the most frequently observed sources we show light curves including 30 m-measurements published in previous papers, Steppe et al. (1988A&AS...75..317S; 1992A&AS...96..441S and and 1993, Cat. <J/A+AS/102/611>)
- ID:
- ivo://CDS.VizieR/J/ApJS/202/1
- Title:
- 1mm spectral line survey toward GLIMPSE EGOs
- Short Name:
- J/ApJS/202/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A northern subsample of 89 Spitzer GLIMPSE extended green objects (EGOs), the candidate massive young stellar objects, are surveyed for molecular lines in two 1GHz ranges: 251.5-252.5 and 260.188-261.188GHz. A comprehensive catalog of observed molecular line data and spectral plots are presented. Eight molecular species are undoubtedly detected: H^13^CO^+^, SiO, SO, CH_3_OH, CH_3_OCH_3_, CH_3_CH_2_CN, HCOOCH_3_, and HN^13^C. The H^13^CO^+^ 3-2 line is detected in 70 EGOs, among which 37 also show the SiO 6-5 line, demonstrating their association with dense gas and supporting the outflow interpretation of the extended 4.5um excess emission. Our major dense gas and outflow tracers (H^13^CO^+^, SiO, SO, and CH_3_OH) are combined with our previous survey of ^13^CO, ^12^CO, and C^18^O 1-0 toward the same sample of EGOs for a multi-line, multi-cloud analysis of linewidth and luminosity correlations.
- ID:
- ivo://CDS.VizieR/J/ApJS/190/348
- Title:
- 1mm spectral survey of IRC+10216 & VY CMa
- Short Name:
- J/ApJS/190/348
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A low noise (1{sigma}rms~3mK) 1mm spectral survey (214.5-285.5GHz) of the oxygen-rich supergiant VY Canis Majoris and the carbon-rich asymptotic giant branch star IRC +10216 has been conducted using the Arizona Radio Observatory's 10m Submillimeter Telescope. Here the complete data set is presented. This study, carried out with a new ALMA-type receiver, marks the first continuous band scan of an O-rich circumstellar envelope, and the most sensitive survey to date of IRC+10216. In VY CMa, 130 distinct molecular lines were detected, 14 of which cannot be identified; in IRC +10216, 717 lines were observed, with 126 features remaining unidentified. In the 1mm bands of VY CMa and IRC +10216, emission is present from 18 and 32 different chemical compounds, respectively, with 10 species common to both sources. Many narrow emission lines were observed in both circumstellar shells, arising from vibrationally excited molecules and from refractory-containing species. Line profiles in VY CMa also exhibit a variety of different shapes, caused by the complex, asymmetric outflow of this object.
- ID:
- ivo://CDS.VizieR/J/ApJ/747/63
- Title:
- 7mm VLBA observations of BL Lac object OJ287
- Short Name:
- J/ApJ/747/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from an ultra-high-resolution 7 mm Very Long Baseline Array study of the relativistic jet in the BL Lacertae object OJ287 from 1995 to 2011 containing 136 total intensity images. Analysis of the image sequence reveals a sharp jet-position-angle swing by >100{deg} during [2004,2006], as viewed in the plane of the sky, which we interpret as the crossing of the jet from one side of the line of sight to the other during a softer- and longer-term swing of the inner jet. Modulating such long-term swing, our images also show for the first time a prominent erratic wobbling behavior of the innermost ~0.4 mas of the jet with fluctuations in position angle of up to ~40{deg} over timescales ~2 yr. This is accompanied by highly superluminal motions along non-radial trajectories, which reflect the remarkable non-ballistic nature of the jet plasma on these scales. The erratic nature and short timescales of the observed behavior rule out scenarios such as binary black hole systems, accretion disk precession, and interaction with the ambient medium as possible origins of the phenomenon on the scales probed by our observations, although such processes may cause longer-term modulation of the jet direction. We propose that variable asymmetric injection of the jet flow, perhaps related to turbulence in the accretion disk, coupled with hydrodynamic instabilities leads to the non-ballistic dynamics that causes the observed non-periodic changes in the direction of the inner jet.