- ID:
- ivo://CDS.VizieR/J/A+A/623/A141
- Title:
- G345.5+1.5 region multiwavelength study
- Short Name:
- J/A+A/623/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The star formation process requires the dust and gas present in the Milky Way to self-assemble into dense reservoirs of neutral material where the new generation of stars will emerge. Star-forming regions are usually studied in the context of Galactic surveys, but dedicated observations are sometimes needed when the study reaches beyond the survey area. A better understanding of the star formation process in the Galaxy can be obtained by studying several regions. This allows increasing the sample of objects (clumps, cores, and stars) for further statistical works and deeper follow-up studies. Here, we studied the G345.5+1.5 region, which is located slightly above the Galactic plane, to understand its star formation properties. We combined Large Apex BOlometer CAmera (LABOCA) and ^12^CO(4-3) transition line (NANTEN2) observations complemented with the Hi-GAL and Spitzer-GLIMPSE surveys to study the star formation toward this region. We used the Clumpfind algorithm to extract the clumps from the 870um and ^12^CO(4-3) data. Radio emission at 36cm was used to estimate the number of HII regions and to remove the contamination from the free-free emission at 870um. We employed color-color diagrams and spectral energy distribution (SED) slopes to distinguish between prestellar and protostellar clumps.We studied the boundedness of the clumps through the virial parameter. Finally, we estimated the star formation efficiency (SFE) and star formation rate (SFR) of the region and used the Schmidt-Kennicutt diagram to compare its ability to form stars with other regions of the Galactic plane. Of the 13 radio sources that we found using the MGPS-2 catalog, 7 are found to be associated with Hii regions corresponding to late-B or early-O stars. We found 45 870um clumps with diameters between 0.4 and 1.2pc and masses between 43M_{sun}_ and 3923M_{sun}_, and 107 ^12^CO clumps with diameters between 0.4 pc and 1.3pc and masses between 28M_{sun}_ and 9433M_{sun}_. More than 50% of the clumps are protostellar and bounded and are able to host (massive) star formation. High SFR and SFR density (S FR) values are associated with the region, with an SFE of a few percent. With submillimeter, CO transition, and short-wavelength infrared observations, our study reveals a population of massive stars, protostellar and bound starless clumps, toward G345.5+1.5. This region is therefore actively forming stars, and its location in the starburst quadrant of the Schmidt-Kennicutt diagram is comparable to other star-forming regions found within the Galactic plane.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/1587
- Title:
- GRS/BGPS sources in Galactic Plane
- Short Name:
- J/MNRAS/431/1587
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The line of sight through the Galactic plane between longitudes l=37.83{deg} and 42.50{deg} allows for the separation of Galactic Ring Survey molecular clouds into those that fall within the spiral arms and those located in the interarm regions. By matching these clouds in both position and velocity with dense clumps detected in the mm continuum by the Bolocam Galactic Plane Survey, we are able to look for changes in the clump formation efficiency (CFE), the ratio of clump to cloud mass, with Galactic environment. We find no evidence of any difference in the CFE between the interarm and spiral-arm regions along this line of sight. This is further evidence that, outside the Galactic Centre region, the large-scale structures of the Galaxy play little part in changing the dense, potentially star-forming structures within molecular clouds.
- ID:
- ivo://CDS.VizieR/J/A+A/570/A30
- Title:
- H{alpha} emission-line stars in M42
- Short Name:
- J/A+A/570/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep survey of H-alpha emission-line stars in the M42 region using wide-field objective prism films. A total of 1699 H{alpha} emission-line stars were identified, of which 1025 were previously unknown, within an area of 5.5{deg}x5.5{deg} centred on the Trapezium Cluster. We present H-alpha strength estimates, positions, and JHKs photometry extracted from 2MASS, and comparisons to previous surveys. The spatial distribution of the bulk of the stars follows the molecular cloud as seen in CO and these stars are likely to belong to the very young population of stars associated with the Orion Nebula Cluster. Additionally, there is a scattered population of H-alpha emission-line stars distributed all over the region surveyed, which may consist partly of foreground stars associated with the young NGC 1980 cluster, as well as some foreground and background dMe or Be stars. The present catalogue adds a large number of candidate low-mass young stars belonging to the Orion population, selected independently of their infrared excess or X-ray emission.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1117
- Title:
- Halpha emission-line stars in NGC2264
- Short Name:
- J/AJ/127/1117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep survey of H{alpha} emission-line stars in the NGC 2264 region using wide-field objective prism films. We find 357 H{alpha} emission-line stars, of which 113 were previously detected, within an area of 3{deg}x3{deg} centered on the Cone Nebula, with a majority of stars being concentrated in a dense cluster at the center of the region. We present a large-scale CO map of NGC 2264 and find a strong correlation between the cluster of H{alpha} emission-line stars and the most massive core in the cloud complex. A more extended halo of stars poorly correlated with the gas may represent stars that have drifted away from their birth place, suggesting that star formation has taken place in NGC 2264 for several million years.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1530
- Title:
- H{alpha} emission stars in LDN988
- Short Name:
- J/AJ/131/1530
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- L988 is a large (~0.5{deg}x0.7{deg}) dark cloud complex at about 600pc that contains several bright pre-main-sequence objects (such as V1331 Cyg and LkH{alpha} 321), but this paper deals in detail only with a small region on its eastern edge, near the HAeBe star LkH{alpha} 324. That star and its distant companion LkH{alpha} 324SE lie at the apex of a V-shaped area apparently excavated from the edge of L988, and are the brightest members of a small cluster containing about 50 H{alpha}-emission stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/3461
- Title:
- Halpha maps of 3 LIRGS
- Short Name:
- J/MNRAS/465/3461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed three luminous infrared galaxy systems (LIRGS) which are pairs of interacting galaxies, with the Galaxy H{alpha} Fabry-Perot system (GH{alpha}FaS) mounted on the 4.2m William Herschel Telescope at the Roque de los Muchachos Observatory, and combined the observations with the Atacama Large Millimeter Array (ALMA) observations of these systems in CO emission to compare the physical properties of the star formation regions and the molecular gas clouds, and specifically the internal kinematics of the star forming regions. We identified 88 star forming regions in the H$\alpha$ emission data-cubes, and 27 molecular cloud complexes in the CO emission data-cubes. The surface densities of the star formation rate and the molecular gas are significantly higher in these systems than in non-interacting galaxies and the Galaxy, and are closer to the surface densities of the star formation rate and the molecular gas of extreme star forming galaxies at higher redshifts. The large values of the velocity dispersion also show the enhanced gas surface density. The HII regions are situated on the {Sigma}_SFR_-{sigma}_v_ envelope, and so are also in virial equilibrium. Since the virial parameter decreases with the surface densities of both the star formation rate and the molecular gas, we claim that the clouds presented here are gravitationally dominated rather than being in equilibrium with the external pressure.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A118
- Title:
- HCN(1-0) cube for the nucleus of M51
- Short Name:
- J/A+A/593/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AGN feedback is invoked as one of the most relevant mechanisms that shape the evolution of galaxies. Our goal is to understand the interplay between AGN feedback and the interstellar medium in M51, a nearby spiral galaxy with a modest AGN and a kpc-scale radio jet expanding through the disc of the galaxy. For that, we combine molecular gas observations in the CO(1-0) and HCN(1-0) lines from the Plateau de Bure interferometer with archival radio, X-ray, and optical data. We show that there is a significant scarcity of CO emission in the ionisation cone, while molecular gas emission tends to accumulate towards the edges of the cone. The distribution and kinematics of CO and HCN line emission reveal AGN feedback effects out to r~500pc, covering the whole extent of the radio jet, with complex kinematics in the molecular gas which displays strong local variations. We propose that this is the result of the almost coplanar jet pushing on molecular gas in different directions as it expands; the effects are more pronounced in HCN than in CO emission, probably as the result of radiative shocks. Following previous interpretation of the redshifted molecular line in the central 5" as caused by a molecular outflow, we estimate the outflow rates to be Mdot_H2~0.9M_{sun}_/yr and dM/dt_dense_~0.6M_{sun}_/yr, which are comparable to the molecular inflow rates (~1M_{sun}_/yr); gas inflow and AGN feedback could be mutually regulated processes. The agreement with findings in other nearby radio galaxies suggests that this is not an isolated case, and probably the paradigm of AGN feedback through radio jets, at least for galaxies hosting low-luminosity active nuclei.
- ID:
- ivo://CDS.VizieR/J/ApJ/903/111
- Title:
- HCN, HNC, H13CN & HC3N of Galactic Center map. II.
- Short Name:
- J/ApJ/903/111
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- We report a statistical analysis exploring the origin of the overall low star formation efficiency (SFE) of the Galactic central molecular zone (CMZ) and the SFE diversity among the CMZ clouds using a wide-field HCN J=4-3 map, whose optically thin critical density (~10^7^/cm^3^) is the highest among the tracers ever used in CMZ surveys. Logistic regression is performed to empirically formulate star formation probability of 195 HCN clumps, 13 of which contain star formation signatures. The explanatory parameters in the best-fit model are reduced into the virial parameter {alpha}_vir_ without significant contribution from other parameters, whereas the performance of the model without {alpha}_vir_ is no better than that using randomly generated data. The threshold {alpha}_vir_ is 6, which translates into a volume density (n_H_2__) of 10^4.6^/cm^3^ with the n_H_2__-{alpha}_vir_ correlation. The scarcity of the low-{alpha}_vir_ clumps, whose fraction to all HCN clumps is 0.1, can be considered as one of the immediate causes of the suppressed SFE. No correlation between the clump size or mass and star formation probability is found, implying that HCN J= 4-3 does not immediately trace the mass of star-forming gas above a threshold density. Meanwhile, star-forming and non-star-forming clouds are degenerate in the physical parameters of the CS J=1-0 clouds, highlighting the efficacy of the HCN J=4-3 line to probe star-forming regions in the CMZ. The timescale of the high-{alpha}_vir_ to low-{alpha}_vir_ transition is <~2Myr, which is consistent with the tidal compression and X1/X2 orbit transition models but possibly does not fit the cloud-cloud collision picture.
- ID:
- ivo://CDS.VizieR/J/ApJ/652/1230
- Title:
- H_2_CO absorption toward Galactic anticenter
- Short Name:
- J/ApJ/652/1230
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a blind search in the general direction of the Galactic anticenter for absorption of the cosmic microwave background (CMB) radiation near 4.83GHz by molecular clouds containing gaseous ortho-formaldehyde (H_2_CO). The observations were done using the 25m radio telescope at Onsala in Sweden and covered strips in Galactic latitude, 1{deg}<=b<=+1{deg}, at several longitudes in the region 170{deg}<=l<=190{deg}. Spectra were obtained in these strips with a grid spacing corresponding to the telescope resolution of 10'. We have detected H_2_CO CMB absorption at 10% of the survey pointings.
- ID:
- ivo://CDS.VizieR/J/A+A/551/A28
- Title:
- H2CO and CO in 4 molecular clouds
- Short Name:
- J/A+A/551/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We seek to understand how the 4.8GHz formaldehyde absorption line is distributed in the MON R2, S156, DR17/L906, and M17/M18 regions. More specifically, we look for the relationship among the H_2_CO, ^12^CO, and ^13^CO spectral lines. The four regions of MON R2 (60'x90'), S156 (50'x70'), DR17/L906 (40'x60'), and M17/M18 (70'x80') were observed for H_2_CO (beam 10'), H110{alpha} recombination (beam 10'), 6 cm continuum (beam 10'), ^12^CO (beam 1'), and ^13^CO (beam 1'). We compared the H_2_CO, ^12^CO, ^13^CO, and continuum distributions, and also the spectra line parameters of H_2_CO, ^12^CO, and ^13^CO. Column densities of H_2_CO, ^13^CO, and H_2_ were also estimated. We found out that the H_2_CO distribution is similar to the ^12^CO and the ^13^CO distributions on a large scale. The correlation between the ^13^CO and the H_2_CO distributions is better than between the ^12^CO and H_2_CO distributions. The H_2_CO and the ^13^CO tracers systematically provide consistent views of the dense regions. Their maps have similar shapes, sizes, peak positions, and molecular spectra and present similar central velocities and line widths. Such good agreement indicates that the H_2_CO and the ^13^CO arise from similar regions.
