- ID:
- ivo://CDS.VizieR/J/A+A/314/615
- Title:
- Maps of the 36 GHz methanol emission
- Short Name:
- J/A+A/314/615
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Effelsberg 100-meter telescope to map the 36GHz 4_-1_->3_0_E methanol transition in galactic star forming regions where methanol masers were previously detected. In most sources, the emission consists in one or several narrow (maser) features superimposed on a broader, presumably quasi-thermal component. The line shapes and positions of the narrow features are often similar to those observed in the other ClassI methanol maser transitions (at 25, 44, 84 and 95GHz), but with some exceptions. Our observations confirm that, unlike the strong ClassII methanol masers (at 12.2, and 6.6GHz), the ClassI methanol masers are offset from the compact HII regions, infrared sources and OH/H_2_O masers. In outflow sources, these are located at the edge of the molecular lobes.
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- ID:
- ivo://CDS.VizieR/J/ApJ/794/81
- Title:
- Maser and infrared studies of oxygen-rich AGB stars
- Short Name:
- J/ApJ/794/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explored an efficient method to identify evolved stars with oxygen-rich envelopes in the late asymptotic giant branch (AGB) or post-AGB phase of stellar evolution, which include a rare class of objects - the "water fountains (WF)." Our method considers the OH and H_2_O maser spectra, the near-infrared Q-parameters (these are color indices accounting for the effect of extinction), and far-infrared AKARI colors. Here we first present the results of a new survey on OH and H_2_O masers. There were 108 color-selected objects: 53 of them were observed in the three OH maser lines (1612, 1665, and 1667 MHz), with 24 detections (16 new for 1612 MHz); and 106 of them were observed in the H_2_O maser line (22 GHz), with 24 detections (12 new). We identify a new potential WF source, IRAS 19356+0754, with large velocity coverages of both OH and H_2_O maser emission. In addition, several objects with high-velocity OH maser emission are reported for the first time. The Q-parameters as well as the infrared [09]-[18] and [18]-[65] AKARI colors of the surveyed objects are then calculated. We suggest that these infrared properties are effective in isolating aspherical from spherical objects, but the morphology may not necessarily be related to the evolutionary status. Nonetheless, by considering altogether the maser and infrared properties, the efficiency of identifying oxygen-rich late/post-AGB stars could be improved.
- ID:
- ivo://CDS.VizieR/J/A+A/417/615
- Title:
- Maser and outflows in UC HII region
- Short Name:
- J/A+A/417/615
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a single-dish survey of molecular outflows towards a homogeneous sample of 136 ultracompact HII regions for which we had previously obtained observations in the methanol 6.7GHz and water 22.2GHz maser lines. The line profiles of the ^13^CO J=1-0 and 2-1 transitions have been compared to those of the corresponding lines of the C^18^O isotopomer to reveal the occurrence of line wings and hence of molecular outflows.
- ID:
- ivo://CDS.VizieR/J/A+A/380/665
- Title:
- Massive dense cores with ^13^CO J=1-0 lines
- Short Name:
- J/A+A/380/665
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports ^13^CO J=1-0 line observations toward 107 IRAS or H2O maser sources with the 13.7m telescope of the Purple Mountain Observatory (PMO). Parameters of emission components are obtained and the profile characteristics are identified. Table1 lists the observed results. It contains source name and its coordinates. ^13^CO line parameters and profile characteristics are given out. Distance, IRAS color indices and bolometric luminosity are also presented.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A21
- Title:
- Massive star-forming regions radio lines
- Short Name:
- J/A+A/550/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Australia Telescope Compact Array (ATCA) observations of the H_2_O maser line and radio continuum at 18.0GHz and 22.8GHz toward a sample of 192 massive star-forming regions containing several clumps already imaged at 1.2mm. The main aim of this study is to investigate the water maser and centimeter continuum emission (that likely traces thermal free-free emission) in sources at different evolutionary stages, using evolutionary classifications previously published. We used the recently comissioned Compact Array Broadband Backend (CABB) at ATCA that obtains images with 20arcsec resolution in the 1.3cm continuum and H_2_O maser emission in all targets. For the evolutionary analysis of the sources we used millimeter continuum emission from the literature and the infrared emission from the MSX Point Source Catalog. We detect centimeter continuum emission in 88% of the observed fields with a typical rms noise level of 0.45mJy/beam. Most of the fields show a single radio continuum source, while in 20% of them we identify multiple components. A total of 214 centimeter continuum sources have been identified, that likely trace optically thin HII regions, with physical parameters typical of both extended and compact HII regions. Water maser emission was detected in 41% of the regions, resulting in a total of 85 distinct components. The low angular (20arcsec) and spectral (14km/s) resolutions do not allow a proper analysis of the water maser emission, but suffice to investigate its association with the continuum sources. We have also studied the detection rate of HII regions in the two types of IRAS sources defined in the literature on the basis of the IRAS colors: High and Low. No significant differences are found, with high detection rates (>90%) for both High and Low sources. We classify the millimeter and infrared sources in our fields in three evolutionary stages following the scheme presented previously: (Type 1) millimeter-only sources, (Type 2) millimeter plus infrared sources, (Type 3) infrared-only sources. We find that HII regions are mainly associated with Type 2 and Type 3 objects, confirming that these are more evolved than Type 1 sources. The HII regions associated with Type 3 sources are slightly less dense and larger in size than those associated with Type 2 sources, as expected if the HII region expands as it evolves, and Type 3 objects are older than Type 2 objects. The maser emission is mostly found to be associated with Type 1 and Type 2 sources, with a higher detection rate toward Type 2, consistent with the results of the literature. Finally, our results on HII region and H_2_O maser association with different evolutionary types confirm the evolutionary classification proposed previously.
- ID:
- ivo://CDS.VizieR/J/A+AS/134/115
- Title:
- Medicina 6.7GHz methanol masers survey
- Short Name:
- J/A+AS/134/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table2 contains the name of the sources and their coordinates (1950) observed, but not detected, with the Medicina Radiotelescope at 6.7GHz in 1995, March. Source are associated with one or more type of phenomena typical of star forming regions (see note 1 for code description). The number of non detected sources is 387.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/128
- Title:
- Megamaser Cosmology Project. VIII. NGC5765B
- Short Name:
- J/ApJ/817/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the Megamaser Cosmology Project, here we present a new geometric distance measurement to the megamaser galaxy NGC 5765b. Through a series of very long baseline interferometry observations, we have confirmed the water masers trace a thin, sub-parsec Keplerian disk around the nucleus, implying an enclosed mass of 4.55+/-0.40x10^7^M_{sun}_. Meanwhile, from single-dish monitoring of the maser spectra over two years, we measured the secular drifts of maser features near the systemic velocity of the galaxy with rates between 0.5 and 1.2km/s/yr. Fitting a warped, thin-disk model to these measurements, we determine a Hubble Constant H_0_ of 66.0+/-6.0km/s/Mpc with an angular-diameter distance to NGC 5765b of 126.3+/-11.6Mpc. Apart from the distance measurement, we also investigate some physical properties related to the maser disk in NGC 5765b. The high-velocity features are spatially distributed into several clumps, which may indicate the existence of a spiral density wave associated with the accretion disk. For the redshifted features, the envelope defined by the peak maser intensities increases with radius. The profile of the systemic masers in NGC 5765b is smooth and shows almost no structural changes over the two years of monitoring time, which differs from the more variable case of NGC 4258.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/118
- Title:
- Megamaser Cosmology Project. XI. Z74-64 VLBI obs.
- Short Name:
- J/ApJ/890/118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the survey component of the Megamaser Cosmology Project, we have discovered a disk megamaser system in the galaxy CGCG 074-064. Using the Green Bank Telescope and the Very Large Array, we have obtained spectral monitoring observations of this maser system at a monthly cadence over the course of two years. We find that the systemic maser features display line-of-sight accelerations of ~4.4km/s/yr that are nearly constant with velocity, while the high-velocity maser features show accelerations that are consistent with zero. We have also used the High-Sensitivity Array to make a high-sensitivity very long baseline interferometric map of the maser system in CGCG 074-064, which reveals that the masers reside in a thin, edge-on disk with a diameter of ~1.5mas (0.6pc). Fitting a three-dimensional warped disk model to the data, we measure a black hole mass of 2.42_-0.20_^+0.22^x10^7^M_{sun}_ and a geometric distance to the system of 87.6_-7.2_^+7.9^Mpc. Assuming a cosmic microwave background-frame recession velocity of 7308+/-150km/s, we constrain the Hubble constant to H_0_=81.0_-6.9_^+7.4^(stat.)+/-1.4(sys.)km/s/Mpc.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A147
- Title:
- Megamaser detection in Seyfert galaxies
- Short Name:
- J/A+A/530/A147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We revisit the relation between H_2_O maser detection rate and nuclear obscuration for a sample of 114 Seyfert galaxies, drawn from the CfA, 12um and IRAS F25/F60 catalogs. These sources have mid-infrared spectra from the Spitzer Space Telescope and they are searched for X-ray and [OIII] (5007{AA}) fluxes from the literature. We use the strength of the [OIV] (25.9um) emission line as tracer for the intrinsic AGN strength. After normalization by [OIV] the observed X-ray flux provides information about X-ray absorption. The distribution of X-ray/[OIV] flux ratios is significantly different for masers and non-masers: The maser detected Seyfert-2s (Sy 1.8-2.0) populate a distinct X-ray/[OIV] range which is, on average, about a factor four lower than the range of Seyfert-2 non-masers and about a factor of ten lower than the range of Seyfert-1s (Sy 1.0-1.5). Non-masers are almost equally distributed over the entire X-ray/[OIV] range. This provides evidence that high nuclear obscuration plays a crucial role for the probability of maser detection. Furthermore, after normalization with [OIV], we find a similar but weaker trend for the distribution of the maser detection rate with the absorption of the 7um dust continuum. This suggests that the obscuration of the 7um continuum occurs on larger spatial scales than that of the X-rays. Hence, in the AGN unified model, at moderate deviation from edge-on, the 7um dust absorption may occur without proportionate X-ray absorption. The absorption of [OIII] appears unrelated to maser detections. The failure to detect masers in obscured AGN is most likely due to insufficient observational sensitivity.
- ID:
- ivo://CDS.VizieR/J/ApJ/854/170
- Title:
- Methanol (CH_3_OH) and OH masers in NGC 6334I
- Short Name:
- J/ApJ/854/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first sub-arcsecond VLA imaging of 6GHz continuum, methanol maser, and excited-state hydroxyl maser emission toward the massive protostellar cluster NGC 6334I following the recent 2015 outburst in (sub)millimeter continuum toward MM1, the strongest (sub)millimeter source in the protocluster. In addition to detections toward the previously known 6.7GHz Class II methanol maser sites in the hot core MM2 and the UCHII region MM3 (NGC 6334F), we find new maser features toward several components of MM1, along with weaker features ~1" north, west, and southwest of MM1, and toward the nonthermal radio continuum source CM2. None of these areas have heretofore exhibited Class II methanol maser emission in three decades of observations. The strongest MM1 masers trace a dust cavity, while no masers are seen toward the strongest dust sources MM1A, 1B, and 1D. The locations of the masers are consistent with a combination of increased radiative pumping due to elevated dust grain temperature following the outburst, the presence of infrared photon propagation cavities, and the presence of high methanol column densities as indicated by ALMA images of thermal transitions. The nonthermal radio emission source CM2 (2" north of MM1) also exhibits new maser emission from the excited 6.035 and 6.030GHz OH lines. Using the Zeeman effect, we measure a line-of-sight magnetic field of +0.5 to +3.7mG toward CM2. In agreement with previous studies, we also detect numerous methanol and excited OH maser spots toward the UCHII region MM3, with predominantly negative line-of-sight magnetic field strengths of -2 to -5mG and an intriguing south-north field reversal.
