- ID:
- ivo://CDS.VizieR/VIII/97
- Title:
- 74MHz VLA Low-frequency Sky Survey Redux (VLSSr)
- Short Name:
- VIII/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a recent re-reduction of the data from the Very Large Array (VLA) Low-frequency Sky Survey (VLSS). We used the VLSS catalogue as a sky model to correct the ionospheric distortions in the data and create a new set of sky maps and corresponding catalogue at 73.8MHz. The VLSS Redux (VLSSr) has a resolution of 75", and an average map rms noise level of {sigma}~0.1Jy/beam. The clean bias is 0.66x{sigma} and the theoretical largest angular size is 36'. Six previously unimaged fields are included in the VLSSr, which has an unbroken sky coverage over 9.3sr above an irregular southern boundary. The final catalogue includes 92964 sources. The VLSSr improves upon the original VLSS in a number of areas including imaging of large sources, image sensitivity, and clean bias; however the most critical improvement is the replacement of an inaccurate primary beam correction which caused source flux errors which vary as a function of radius to nearest pointing centre in the VLSS.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/477/125
- Title:
- Microquasar candidates
- Short Name:
- J/A+A/477/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Microquasars are ideal natural laboratories for understanding accretion/ejection processes, studying the physics of relativistic jets, and testing gravitational phenomena. Nevertheless, these objects are difficult to find in our Galaxy. The main goal of this work is to increase the number of known systems of this kind, which should allow better testing of high-energy phenomena and more realistic statistical studies of this galactic population to be made. We have developed an improved search strategy based on positional cross-identification with very restrictive selection criteria to find new MQs, taking advantage of more sensitive modern X-ray data. To do this, we made combined use of the radio, infrared, and X-ray properties of the sources, using different available catalogs.
- ID:
- ivo://CDS.VizieR/J/A+A/570/A110
- Title:
- Mid-IR properties of OH maser galaxies
- Short Name:
- J/A+A/570/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compiled all 119 OH maser galaxies (110 out of them are megamasers, i.e., L_OH_>10L_{sun}_) published so far and cross-identified these OH masers with the Wide-Field Infrared Survey Explorer (WISE) catalog, to investigate the middle infrared (MIR) properties of OH maser galaxies. The WISE magnitude data at the 3.4, 4.6, 12 and 22{mu}m (W1 to W4) are collected for the OH maser sample and one control sample, which are non-detection sources. The color-color diagrams show that both OH megamaser (OHM) and non-OHM (ultra)luminous infrared galaxies ((U)LIRGs) are far away from the single blackbody model line and many of them can follow the path described by the power-law model. The active galaxy nuclei (AGN) fraction is about ~40% for both OHM and non-OHM (U)LIRGs, according to the AGN criteria W1-W2>=0.8. Among the Arecibo survey sample, OHM sources tend to have a lower luminosity at short MIR wavelengths (e.g., 3.4{mu}m and 4.6{mu}m) than that of non-OHM sources, which should come from the low OHM fraction among the survey sample with large 3.4{mu}m and 4.6{mu}m luminosity. The OHM fraction tends to increase with cooler MIR colors (larger F_22{mu}m_/F_3.4{mu}m_). These may be good for sample selection when searching OH megamasers, such as excluding extreme luminous sources at short MIR wavelengths, choosing sources with cooler MIR colors. In the case of the power-law model, we derived the spectral indices for our samples. For the Arecibo survey sample, OHM (U)LIRGs tend to have larger spectral index {alpha}_22-12_ than non-OHM sources, which agrees with previous results. One significant correlation exists between the WISE infrared luminosity at 22{mu}m and the color [W1]-[W4] for the Arecibo OHM hosts. These clues should provide suitable constraints on the sample selection for OH megamaser surveys by future advanced telescopes (e.g., FAST). In addition, the correlation of maser luminosity and the MIR luminosity of maser hosts tends to be non-significant, which may indirectly support the pumping of OHM emission that is dominated by the far infrared radiation, instead of the MIR radiation.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A96
- Title:
- Mid-J CO shock tracing observations of IRDCs II
- Short Name:
- J/A+A/587/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Infrared dark clouds are kinematically complex molecular structures in the interstellar medium that can host sites of massive star formation. We present maps measuring 4 square arcminutes of the ^12^CO, ^13^CO, and C^18^O J=3 to 2 lines from selected locations within the C and F (G028.37+00.07 and G034.43+00.24) infrared dark clouds (IRDCs), as well as single pointing observations of the ^13^CO and C^18^O J=2 to 1 lines towards three cores within these clouds. We derive CO gas temperatures throughout the maps and find that CO is significantly frozen out within these IRDCs. We find that the CO depletion tends to be the highest near column density peaks with maximum depletion factors between 5 and 9 in IRDC F and between 16 and 31 in IRDC C. We also detect multiple velocity components and complex kinematic structure in both IRDCs. Therefore, the kinematics of IRDCs seem to point to dynamically evolving structures yielding dense cores with considerable depletion factors.
- ID:
- ivo://CDS.VizieR/J/ApJS/145/329
- Title:
- Millennium Arecibo 21-cm Survey
- Short Name:
- J/ApJS/145/329
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We review the theory of measuring spectral lines in emission/ absorption observations and apply it to a new survey of the 21-cm line against 79 continuum sources. We develop an observing technique and least-squares procedure to determine the opacity profile, the expected emission profile, and their uncertainty profiles. We discuss the radiative transfer for the two-component interstellar HI gas and use Gaussian components, separate ones for the warm and cold neutral media (WNM and CNM), as a practical implementation of a simple but physically correct model that successfully treats both simple and complicated profiles.
- ID:
- ivo://CDS.VizieR/J/ApJS/151/271
- Title:
- Millennium Arecibo 21-cm Survey. III.
- Short Name:
- J/ApJS/151/271
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We outline the theory and practice of measuring the four Stokes parameters of spectral lines in emission/absorption observations. We apply these concepts to our Arecibo H I absorption line data and present the results. We include a detailed discussion of instrumental effects arising from polarized beam structure and its interaction with the spatially extended emission line structure. At Arecibo, linear polarization [Stokes (Q,U)] has much larger instrumental effects than circular (Stokes V). We show how to reduce the instrumental contributions to V and to evaluate upper limits to its remaining instrumental errors by using the (Q,U) results. These efforts work well for opacity spectra but not for emission spectra. Arecibo's large central blockage exacerbates these effects, particularly for emission profiles, and other telescopes with weaker sidelobes are not as susceptible. We present graphical results for 41 sources; we analyze these absorption spectra in terms of Gaussian components, which number 136, and present physical parameters including magnetic field for each.
- ID:
- ivo://CDS.VizieR/J/A+A/476/1243
- Title:
- Millimeter continuum mapping of Cygnus X
- Short Name:
- J/A+A/476/1243
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a millimeter continuum survey of the entire Cygnus X molecular complex. We used the MAMBO and MAMBO-2 bolometer arrays on the IRAM 30m telescope to map a 3deg^2^ area at 1.2mm (see fits files of Figures 2, kept to 11" resolution). Our MAMBO-2 imaging gives a complete view of the cloud structures ranging from 0.03pc to 5pc, i.e. from dense cores to clumps. We perform a multi-resolution analysis to extract 129 compact dense cores (~0.1pc, see Table 1) and identify 40 massive large-scale clumps (~0.7pc, see Table 2). The 21um fluxes arising from dense cores are taken from the MSX point source catalog (MSX C6, Cat. <V/114>).
- ID:
- ivo://CDS.VizieR/J/A+A/602/A37
- Title:
- Millimeter RRL in ATLASGAL-selected massive clumps
- Short Name:
- J/A+A/602/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of millimeter wavelength radio recombination lines (mm-RRLs) are used to search for HII regions in an unbiased way that is complementary to many of the more traditional methods previously used (e.g., radio continuum, far-infrared colors, maser emission). The mm-RRLs can be used to derive physical properties of HII regions and to provide velocity information of ionized gas. We carried out targeted mm-RRL observations (39<= principal quantum number (n) <=65 and {Delta}n = 1, 2, 3, and 4, named Hn{alpha}, Hn{beta}, Hn{gamma}, and Hn{delta}) using the IRAM 30m and Mopra 22m telescopes. In total, we observed 976 compact dust clumps selected from a catalog of ~10000 sources identified by the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). The sample was selected to ensure a representative mix of star-forming and quiescent clumps such that a variety of different evolutionary stages is represented. Approximately half of the clumps are mid-infrared quiet while the other half are mid-infrared bright. We detected Hn{alpha} mm-RRL emission toward 178 clumps; Hn{beta}, Hn{gamma}, and Hn{delta} were also detected toward 65, 23, and 22 clumps, respectively. This is the largest sample of mm-RRLs detections published to date. Comparing the positions of these clumps with radio continuum surveys we identified compact radio counterparts for 134 clumps, confirming their association with known HII regions. The nature of the other 44 detections is unclear, but 8 detections are thought to be potentially new HII regions while the mm-RRL emission from the others may be due to contamination from nearby evolved HII regions. Broad linewidths are seen toward nine clumps (linewidth>40km/s) revealing significant turbulent motions within the ionized gas; in the past, such wide linewidths were found toward very compact and dense HII regions. We find that the systemic velocity of the associated dense molecular gas, traced by H^13^CO^+^(1-0), is consistent with the mm-RRL velocities and confirms them as embedded HII regions. We also find that the linewidth of the H^13^CO^+^(1-0) emission is significantly wider than those without mm-RRL detection, indicating a physical connection between the embedded H II region and their natal environments. We also find a correlation between the integrated fluxes of the mm-RRLs and the 6cm continuum flux densities of their radio counterparts (the correlation coefficient, {rho}, is 0.70). By calculating the electron densities we find that the mm-RRL emission is associated with HII regions with n_e_<10^5^cm^3^ and HII region diameter >0.03pc. We detected mm-RRLs toward 178 clumps and identified eight new HII region candidates. The broad mm-RRL from nine clumps may indicate that they arise in very young hyper-compact HII regions. The mm-RRLs trace the radio continuum sources detected by high-resolution observations and their line parameters show associations with the embedded radio sources and their parental molecular clumps.
- 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.
- 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.