Search

Start Over Subject radio astronomy
1011. Millimetre observations of carbon stars. I.
ID:
ivo://CDS.VizieR/J/A+A/390/501
Title:
Millimetre observations of carbon stars. I.
Short Name:
J/A+A/390/501
Date:
21 Oct 2021
Publisher:
CDS
Description:
Millimetre observations of IRAS selected red carbon stars are presented. About 260 stars have been observed with SEST and IRAM in the CO (1-0) and CO (2-1) lines and partially in HCN (1-0) and SiO (3-2). An overall detection rate, in at least one line, of about 80% is achieved. The survey represents the second largest survey for AGB stars, and the largest ever for carbon stars. Two new detections in SiO (3-2) in carbon stars are reported. When available, the SiO/HCN and HCN/CO(1-0) line ratios are consistent with the ratios expected for carbon stars.
1012. MIPS 24um observations of the HDFS
ID:
ivo://CDS.VizieR/J/ApJ/723/1110
Title:
MIPS 24um observations of the HDFS
Short Name:
J/ApJ/723/1110
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present MIPS 24um observations of the Hubble Deep Field South taken with the Spitzer Space Telescope. The resulting image is 254arcmin^2^ in size and has a sensitivity ranging between ~12 and ~30uJy rms, with a median sensitivity of ~20uJy rms. A total of 495 sources have been catalogued with a signal-to-noise ratio greater than 5{sigma}. The source catalog is presented as well as source counts which have been corrected for completeness and flux boosting. The IR sources are then combined with MUSYC optical/NIR and ATHDFS radio observations to obtain redshifts and radio flux densities of the sample. We use the IR/radio flux density ratio (q_24_) to explore the IR-radio correlation for this IR sample and find q_24_=0.71+/-0.31 for sources detected in both IR and radio. The results are extended by stacking IR sources not detected in the radio observations and we derive an average q_24_ for redshift bins between 0<z<2.5. We find that the high-redshift (z>1) sources have an average q_24_ ratio which is better fit by local LIRG SEDs rather than local ULIRG SEDs, indicating that high-redshift ULIRGs differ in their IR/radio properties. So, ULIRGs at high-redshift have SEDs different from those found locally. Infrared-faint radio sources are examined, and while nine radio sources do not have an MIPS detection and are therefore radio-loud active galactic nuclei (AGNs), only one radio source has an extreme IRAC 3.6um to radio flux density ratio indicating it is a radio-loud AGN at z>1.
1013. Miyun 232MHz survey
ID:
ivo://CDS.VizieR/VIII/44
Title:
Miyun 232MHz survey
Short Name:
VIII/44
Date:
21 Oct 2021
Publisher:
CDS
Description:
A meter-wave survey of the sky region north of declination +30{deg} has been carried out with the Miyun Synthesis Radio Telescope (MSRT), Beijing Astronomical Observatory, at 232MHz. It is a moderately deep survey. The observations were made between January 1985 and December 1993. The covered sky area is divided into 156 fields of view. Basically all adjacent fields are separated by 8 degree angular distance. Fields #54, #56, #115, #116, have no data yet. A catalog of 34462 radio sources is given in Table 2. Table3 shows the information on the 152 fields of view.
1014. Miyun 232MHz survey: reliability study
ID:
ivo://CDS.VizieR/J/other/AcApS/16.103
Title:
Miyun 232MHz survey: reliability study
Short Name:
J/other/AcApS/16
Date:
21 Oct 2021
Publisher:
CDS
Description:
A meter-wave sky survey of the region north of declination +30deg has been carried out with the Miyun Synthesis Radio Telescope (MSRT) at 232MHz. The Miyun general catalogue (MGC) contains 26957 radio sources except those located in the galactic plane, its electronic version is available now. Completeness and uniformity of the MGC has been discussed recently (Peng et al, 1995AcApS..15..383P). In this paper, we provide evidence of reliability of the MGC by comparing the MSRT data with other published radio catalogues and also by analyzing the reason why part of the detected sources in the MGC could not be recorded by previous surveys.
1015. mJy radio sources at 1.4 GHz
ID:
ivo://CDS.VizieR/J/ApJS/103/331
Title:
mJy radio sources at 1.4 GHz
Short Name:
J/ApJS/103/331
Date:
21 Oct 2021
Publisher:
CDS
Description:
From the 1.4GHz radio survey of Condon, Dickey, & Salpeter (Cat. <J/AJ/99/1071>) in a region much devoid of rich galaxy clusters at redshifts z<0.43 we selected a "distant" sample of 57 radio sources complete to a 1.4GHz flux density of 35mJy and a "nearby" sample of 36 mostly weaker radio sources which are optically brighter than B~19mag. Our ultimate goals are (1) to study the radio, optical, and near-IR properties of those high-redshift (z~1), moderate-power radio sources in the distant sample and to compare them with that of more powerful radio sources, and (2) to make a comparison of primarily noncluster radio sources in the nearby sample with a companion survey of radio sources in a pair of rich superclusters at z~0.1. In this first paper of a series, we report our new C-array VLA continuum snapshots at 4.86GHz and optical R-band CCD imaging photometry for these two samples and tabulate the observational results on individual sources. Some direct sample statistical properties are also discussed in the paper and summarized as follows: (1) The distant sample: (a) The sample median flux density at 1.4GHz is about 65mJy. (b) The majority (80%) of the sample sources have a steep spectrum between 1.4 and 4.86GHz with a spectral index around 0.9. Nineteen (90%) of the 21 sources that are fully resolved at 4.86 GHz (i.e., angular sizes {theta}>11") have a radio morphology of Fanaroff-Riley (FR) II type. (c) Thirty-seven (88%) of the 42 optically imaged sample sources were optically identified to a limiting R-band magnitude of R~23.5mag. About 15% of the identified radio sources appear to be point sources, and the others are extended galaxies with an appearance similar to nearby elliptical galaxies. (d) Twenty-eight (76%) of the optically identified sources have R>20mag, suggesting that these are probably distant (z>0.8), with a redshift distribution peaking at z~1, where their radio luminosities are about 10 times the break power between the FR I and II classes. (e) We found no strong evidence for the radio and optical axes of the resolved radio sources (i.e., {theta}>5") to be correlated or anticorrelated, nor any evidence for strong clustering around sample radio sources on average. (2) The nearby sample: except for R<15, the sample is dominated by elliptical galaxies with 16<R<18.5mag and a spectral index distribution similar to that of the distant sample. Based on the radial distribution of optical objects around each radio source, we found that the average radio source environment becomes richer from that characteristic of galaxy groups for R<17mag (z<0.2) to that of galaxy groups to clusters at R>18mag (z>0.3) .
1016. M83 magnetic and gaseous spiral arms images
ID:
ivo://CDS.VizieR/J/A+A/585/A21
Title:
M83 magnetic and gaseous spiral arms images
Short Name:
J/A+A/585/A21
Date:
21 Oct 2021
Publisher:
CDS
Description:
The magnetic field configurations in several nearby spiral galaxies contain magnetic arms that are sometimes located between the material arms. The nearby barred galaxy M83 provides an outstanding example of a spiral pattern seen in tracers of gas and magnetic field. We analyse the spatial distribution of magnetic fields in M83 and their relation to the material spiral arms. Isotropic and anisotropic wavelet transforms are used to decompose the images of M83 in various tracers to quantify structures in a range of scales from 0.2 to 10kpc. We used radio polarization observations at {lambda}6.2cm and {lambda}13cm obtained with the VLA, Effelsberg and ATCA telescopes and APEX sub-mm observations at 870{mu}m, which are first published here, together with maps of the emission of warm dust, ionized gas, molecular gas, and atomic gas. The spatial power spectra are similar for the tracers of dust, gas, and total magnetic field, while the spectra of the ordered magnetic field are significantly different. As a consequence, the wavelet cross-correlation between all material tracers and total magnetic field is high, while the structures of the ordered magnetic field are poorly correlated with those of other tracers. The magnetic field configuration in M83 contains pronounced magnetic arms. Some of them are displaced from the corresponding material arms, while others overlap with the material arms. The pitch angles of the magnetic and material spiral structures are generally similar. The magnetic field vectors at {lambda}6.2cm are aligned with the outer material arms, while significant deviations occur in the inner arms and, in particular, in the bar region, possibly due to non-axisymmetric gas flows. Outside the bar region, the typical pitch angles of the material and magnetic spiral arms are very close to each other at about 10{deg}. The typical pitch angle of the magnetic field vectors is about 20{deg} larger than that of the material spiral arms. One of the main magnetic arms in M83 is displaced from the gaseous arms similarly to the galaxy NGC6946, while the other main arm overlaps a gaseous arm, similar to what is observed in M51. We propose that a regular spiral magnetic field generated by a mean-field dynamo is compressed in material arms and partly aligned with them. The interaction of galactic dynamo action with a transient spiral pattern is a promising mechanism for producing such complicated spiral patterns as in M83.
1017. 1.3mm and 3mm emission maps or 4 Ae/Be stars
ID:
ivo://CDS.VizieR/J/A+A/531/A50
Title:
1.3mm and 3mm emission maps or 4 Ae/Be stars
Short Name:
J/A+A/531/A50
Date:
21 Oct 2021
Publisher:
CDS
Description:
Herbig Ae stars (HAe) are the precursors of Vega-type systems and, therefore, crucial objects in planet formation studies. Thus far, only a few disks associated with HAe stars have been studied using millimetre interferometers. Our aim is to determine the dust evolution and the lifetime of the disks associated with Herbig Ae stars. We imaged the continuum emission at ~3mm and ~1.3mm of the Herbig Ae/Be stars BD+61154, RR Tau, VY Mon and LkH{alpha} 198 using the Plateau de Bure Interferometer (PdBI). These stars are in the upper end of the stellar mass range of the Herbig Ae stars (M_*_>3M_{sun}_). Our measurements were used to complete the Spectral Energy Distribution (SED). The modelling of the SED, in particular the FIR-mm part, allow us to determine the masses and dust properties of these disks. We detected the disks associated with BD+61154, RR Tau and VY Mon with disk masses of 0.35M_{sun}_, 0.05M_{sun}_ and 0.40M_{sun}_ respectively. The disk around LkH{alpha} 198 was not detected with an upper limit to the disk mass of 0.004M_{sun}_. We detected, however, the disks associated with the younger stellar objects LkH{alpha} 198--IR and LkH{alpha} 198--mm that are located in the vicinity of LkH{alpha} 198. The fitting of the mm part of the SED reveal that the grains in the mid-plane of the disks around BD+61154, RR Tau and VY Mon have sizes of ~1-1000um. Therefore, grains have not grown to centimetre sizes in these disks yet. These massive (M_*_>3M_{sun}_) and young (~1Myr) HAe stars are surrounded by massive (>~0.04M_{sun}_) disks with grains of micron-millimetre sizes. Although grain growth is proceeding in these disks, their evolutionary stage is prior to the formation of planetesimals. These disks are less evolved than those detected around T Tauri and Herbig Be stars.
1018. 1.4mm and 3mm interferometry of IRAS 19410+2336
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.
1019. mm continuum and line images of G0.253+0.016
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.
1020. 1.2-mm dust clumps with luminous water masers
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.