- ID:
- ivo://CDS.VizieR/J/A+A/474/1093
- Title:
- 30GHz flux densities of CJF sources
- Short Name:
- J/A+A/474/1093
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim was to measure the 30-GHz flux densities of the 293 sources in the Caltech-Jodrell Bank flat-spectrum (CJF) sample. The measurements are part of an ongoing programme to measure the spectral energy distributions of flat spectrum radio sources and to correlate them with the milliarcsecond structures from VLBI and other measured astrophysical properties. The 30-GHz data were obtained with a twin-beam differencing radiometer system mounted on the Torun 32-m telescope. The system has an angular resolution of 1.2arcmin. Together with radio spectral data obtained from the literature, the 30-GHz data have enabled us to identify 42 of the CJF sources as Giga-hertz Peaked Spectrum (GPS) sources. Seventeen percent of the sources have rising spectra (alpha>0) between 5 and 30GHz.
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- ID:
- ivo://CDS.VizieR/J/ApJ/488/224
- Title:
- 4.85 GHz fluxes of H II regions
- Short Name:
- J/ApJ/488/224
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an all-sky flux catalog of 760 H II regions with angular sizes ranging up to 10' at 4.85GHz. The data were compiled in a self-consistent manner from existing images of the Green Bank and Parkes-MIT-NRAO 4.85GHz radio continuum surveys. Nearly 35% of these H II regions have fluxes measured from these surveys for the first time. We compared our results to the previously published source catalogs which fit the same data. The new flux measurements agree within 5%-7% of these values and fall well within the formal errors. The diameters fall within 16% of the previously published fits to the same data, within the formal uncertainties of these values.
- ID:
- ivo://CDS.VizieR/J/ApJ/769/20
- Title:
- 22GHz H_2_O maser survey toward IR sources
- Short Name:
- J/ApJ/769/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a 22GHz H_2_O maser survey toward a new sample of asymptotic giant branch (AGB) and post-AGB star candidates. Most of the objects are selected for the first time based on the AKARI data, which have high flux sensitivity in the mid-infrared ranges. We aim at finding H_2_O maser sources in the transient phase between the AGB and post-AGB stages of evolution, where the envelopes start to develop large deviations from spherical symmetry. The observations were carried out with the Effelsberg 100m radio telescope. Among 204 observed objects, 63 detections (36 new) were obtained. We found four objects that may be "water fountain" sources (IRAS 15193+3132, IRAS 18056-1514, OH 16.3-3.0, and IRAS 18455+0448). They possess an H_2_O maser velocity coverage much smaller than those in other known water fountains. However, the coverage is still larger than that of the 1612MHz OH maser. It implies that there is an outflow with a higher velocity than the envelope expansion velocity (typically <=25km/s), meeting the criterion of the water fountain class. We suggest that these candidates are possibly oxygen-rich late AGB or early post-AGB stars in a stage of evolution immediately after the spherically symmetric AGB mass loss has ceased.
5434. 22GHz image of 3C 273
- ID:
- ivo://CDS.VizieR/J/A+A/604/A111
- Title:
- 22GHz image of 3C 273
- Short Name:
- J/A+A/604/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- RadioAstron is a 10m orbiting radio telescope mounted on the Spektr-R satellite, launched in 2011, performing Space Very Long Baseline Interferometry (SVLBI) observations supported by a global ground array of radio telescopes. With an apogee of ~350000km, it is offering for the first time the possibility to perform as-resolution imaging in the cm-band. The RadioAstron Active Galactic Nuclei (AGN) polarization Key Science Project (KSP) aims at exploiting the unprecedented angular resolution provided by RadioAstron to study jet launching/collimation and magnetic-field configuration in AGN jets. The targets of our KSP are some of the most powerful blazars in the sky. We present observations at 22GHz of 3C 273, performed in 2014, designed to reach a maximum baseline of approximately nine Earth diameters. Reaching an angular resolution of 0.3mas, we study a particularly low-activity state of the source, and estimate the nuclear region brightness temperature, comparing with the extreme one detected one year before during the RadioAstron early science period.We also make use of the VLBA-BU-BLAZAR survey data, at 43GHz, to study the kinematics of the jet in a ~1.5-year time window. We find that the nuclear brightness temperature is two orders of magnitude lower than the exceptionally high value detected in 2013 with RadioAstron at the same frequency (1.4x10^13^K, source-frame), and even one order of magnitude lower than the equipartition value. The kinematics analysis at 43 GHz shows that a new component was ejected ~2 months after the 2013 epoch, visible also in our 22GHz map presented here. Consequently this was located upstream of the core during the brightness temperature peak. Fermi-LAT observations for the period 2010-2014 do not show any gamma-ray flare in conjunction with the passage of the new component by the core at 43GHz. These observations confirm that the previously detected extreme brightness temperature in 3C 273, exceeding the inverse Compton limit, is a short-lived phenomenon caused by a temporary departure from equipartition. Thus, the availability of interferometric baselines capable of providing as angular resolution does not systematically imply measured brightness temperatures over the known physical limits for astrophysical sources.
- ID:
- ivo://CDS.VizieR/J/AJ/123/1784
- Title:
- 1.4 GHz imaging of the Bootes field
- Short Name:
- J/AJ/123/1784
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from our deep (16x12hr) Westerbork Synthesis Radio Telescope (WSRT) observations of the approximately 7{deg}^2^ Bootes Deep Field, centered at 14h 32min 05.75s, 34{deg} 16' 47.5" (J2000.0). Our survey consists of 42 discrete pointings, with enough overlap to ensure a uniform sensitivity across the entire field, with a limiting sensitivity of 28{mu}Jy (1{sigma}_rms_). The catalog contains 3172 distinct sources, of which 316 are resolved by the 13"x27" beam. The Bootes field is part of the optical/near-infrared imaging and spectroscopy survey effort conducted at various institutions. The combination of these data sets and the deep nature of the radio observations will allow unique studies of a large range of topics including the redshift evolution of the luminosity function of radio sources, the K-z relation, the clustering environment of radio galaxies, the radio/far-infrared correlation for distant starbursts, and the nature of obscured radio-loud active galactic nuclei. The observations were carried out by the WSRT operating at 1.380GHz. The WSRT consists of 14 25m-telescopes arranged in a 2.7km east-west configuration. As the back end, we used the digital continuum back end with eight subbands of 10MHz bandwidth each. The smallest baseline (9-A) was set to 54m to limit shadowing at the expense of a reduction in large spatial structure sensitivity (~800" for this minimum baseline and frequency).
- ID:
- ivo://CDS.VizieR/J/ApJ/831/168
- Title:
- 6GHz JVLA observations of low-z SDSS quasars
- Short Name:
- J/ApJ/831/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss 6GHz JVLA observations covering a volume-limited sample of 178 low-redshift (0.2<z<0.3) optically selected quasi-stellar objects (QSOs). Our 176 radio detections fall into two clear categories: (1) about 20% are radio-loud QSOs (RLQs) with spectral luminosities of L_6_>~10^23.2^W/Hz that are primarily generated in the active galactic nucleus (AGN) responsible for the excess optical luminosity that defines a bona fide QSO; and (2) the remaining 80% that are radio-quiet QSOs (RQQs) that have 10^21^<~L_6_<~10^23.2^W/Hz and radio sizes <~10kpc, and we suggest that the bulk of their radio emission is powered by star formation in their host galaxies. "Radio-silent" QSOs (L_6_<~10^21^W/Hz) are rare, so most RQQ host galaxies form stars faster than the Milky Way; they are not "red and dead" ellipticals. Earlier radio observations did not have the luminosity sensitivity of L_6_<~10^21^W/Hz that is needed to distinguish between such RLQs and RQQs. Strong, generally double-sided radio emission spanning >>10kpc was found to be associated with 13 of the 18 RLQ cores with peak flux densities of S_p_>5mJy/beam (log(L)>~24). The radio luminosity function of optically selected QSOs and the extended radio emission associated with RLQs are both inconsistent with simple "unified" models that invoke relativistic beaming from randomly oriented QSOs to explain the difference between RLQs and RQQs. Some intrinsic property of the AGNs or their host galaxies must also determine whether or not a QSO appears radio-loud.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A106
- Title:
- 36GHz methanol lines from nearby galaxies
- Short Name:
- J/A+A/633/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Methanol (CH_3_OH) is one of the most abundant interstellar molecules, offering a vast number of transitions to be studied, including many maser lines. However, while the strongest Galactic CH_3_OH lines, the so-called class II masers, show no indications for the presence of superluminous counterparts in external galaxies, the less luminous Galactic class I sources appear to be different. Here we report class I 36GHz ({lambda}~=0.8cm) CH_3_OH 4_-1_ --> 3_0_ E line emission from the nearby galaxies Maffei 2 (D~=6Mpc) and IC 342 (D~=3.5Mpc), measured with the 100m telescope at Effelsberg at three different epochs within a time span of about five weeks. The 36GHz methanol line of Maffei 2 is the second most luminous among the sources detected with certainty outside the Local Group of galaxies. This is not matched by the moderate infrared luminosity of Maffei 2. Higher-resolution data are required to check whether this is related to its prominent bar and associated shocks. Upper limits for M 82, NGC 4388, NGC 5728 and Arp 220 are also presented. The previously reported detection of 36GHz maser emission in Arp 220 is not confirmed. Nondetections are reported from the related class I 44GHz ({lambda}~=0.7cm) methanol transition towards Maffei 2 and IC 342, indicating that this line is not stronger than its 36GHz counterpart. In contrast to the previously detected 36GHz CH3OH emission in NGC 253 and NGC 4945, our 36GHz profiles towards Maffei 2 and IC 342 are similar to those of previously detected nonmasing lines from other molecular species. However, by analogy to our Galactic center region, it may well be possible that the 36GHz methanol lines in Maffei 2 and IC 342 are composed of a large number of faint and narrow maser features that remain spatially unresolved. In view of this, a search for a weak broad 36GHz line component would also be desirable in NGC 253 and NGC 4945.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A130
- Title:
- 6.7GHz methanol maser polarization in MSFRs IV
- Short Name:
- J/A+A/623/A130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Magnetohydrodynamical simulations show that the magnetic field can drive molecular outflows during the formation of massive protostars. The best probe to observationally measure both the morphology and the strength of this magnetic field at scales of 10-100au is maser polarization. Measuring the direction of magnetic fields at milliarcsecond resolution around a sample of massive star forming regions to determine whether there exists a relation between the orientation of the magnetic field and of the outflows. In addition by estimating the magnetic field strength via the Zeeman splitting measurements, the role of magnetic field in the dynamics of the massive star-forming region is investigated. We selected a flux-limited sample of 31 massive star-forming regions to perform a statistical analysis of the magnetic field properties with respect to the molecular outflows characteristics. We report the linearly and circularly polarized emission of 6.7GHz CH_3_OH masers towards seven massive star-forming regions of the total sample with the European VLBI Network. The sources are: G23.44-0.18, G25.83-0.18, G25.71-0.04, G28.31-0.39, G28.83-0.25, G29.96-0.02, and G43.80-0.13. We identified a total of 219 CH_3_OH maser features, 47 and 2 of which showed linearly and circularly polarized emission, respectively. We measured well ordered linear polarization vectors around all the massive young stellar objects and Zeeman splitting towards G25.71-0.04 and G28.83-0.25. Thanks to recent theoretical results, we were able to provide lower limits to the magnetic field strength from our Zeeman splitting measurements. We further confirm (based on ~80% of the total flux-limited sample) that the magnetic field on scales of 10-100 au is preferentially oriented along the outflow axes. The estimated magnetic field strength of |B_||_|>61mG and >21mG towards G25.71-0.04 and G28.83-0.2, respectively, indicates that it dominates the dynamics of the gas in both regions.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A102
- Title:
- 6.7GHz methanol maser polarization in SFR
- Short Name:
- J/A+A/578/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Theoretical simulations and observations at different angular resolutions have shown that magnetic fields have a central role in massive star formation. Like in low-mass star formation, the magnetic field in massive young stellar objects can either be oriented along the outflow axis or randomly. Measuring the magnetic field at milliarcsecond resolution (10-100au) around a substantial number of massive young stellar objects permits determining with a high statistical significance whether the direction of the magnetic field is correlated with the orientation of the outflow axis or not. In late 2012, we started a large VLBI campaign with the European VLBI Network to measure the linearly and circularly polarized emission of 6.7GHz CH_3_OH masers around a sample of massive star-forming regions. This paper focuses on the first seven observed sources, G24.78+0.08, G25.65+1.05, G29.86-0.04, G35.03+0.35, G37.43+1.51, G174.20-0.08, and G213.70-12.6. For all these sources, molecular outflows have been detected in the past. We detected a total of 176 CH_3_OH masing cloudlets toward the seven massive star-forming regions, 19% of which show linearly polarized emission. The CH_3_OH masers around the massive young stellar object MM1 in G174.20-0.08 show neither linearly nor circularly polarized emission. The linear polarization vectors are well ordered in all the other massive young stellar objects. We measured significant Zeeman splitting toward both A1 and A2 in G24.78+0.08, and toward G29.86-0.04 and G213.70-12.6. By considering all the 19 massive young stellar objects reported in the literature for which both the orientation of the magnetic field at milliarcsecond resolution and the orientation of outflow axes are known, we find evidence that the magnetic field (on scales 10-100au) is preferentially oriented along the outflow axes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/3461
- Title:
- 6.7-GHz methanol masers-dust associations
- Short Name:
- J/MNRAS/446/3461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of 870{mu}m continuum observations, using the Large APEX Bolometer Camera, towards 77 class-II, 6.7-GHz methanol masers identified by the Methanol MultiBeam (MMB) survey to map the thermal emission from cool dust towards these objects. These data complement a study of 630 methanol masers associated with compact dense clumps identified from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) survey. Compact dust emission is detected towards 70 sources, which implies a dust-association rate of 99 per cent for the full MMB catalogue. Evaluation of the derived dust and maser properties leads us to conclude that the combined sample represents a single population tracing the same phenomenon. We find median clump masses of a few 10^3^M_{sun}_ and that all but a handful of sources satisfy the mass-size criterion required for massive star formation. This study provides the strongest evidence of the almost ubiquitous association of methanol masers with massive, star-forming clumps. The fraction of methanol-maser associated clumps is a factor of ~2 lower in the outer Galaxy than the inner Galaxy, possibly a result of the lower metallicity environment of the former. We find no difference in the clump-mass and maser-luminosity distributions of the inner and outer Galaxy. The maser-pumping and clump formation mechanisms are therefore likely to be relatively invariant to Galactic location. Finally, we use the ratio of maser luminosity and clump mass to investigate the hypothesis that the maser luminosity is a good indicator of the evolutionary stage of the embedded source, however, we find no evidence to support this.