- ID:
- ivo://CDS.VizieR/J/ApJS/241/18
- Title:
- A 6.7GHz methanol maser survey. II. |b|<2{deg}
- Short Name:
- J/ApJS/241/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of our systematic survey for Galactic 6.7GHz Class II CH_3_OH maser emission toward a sample of young stellar objects. The survey was conducted with the Shanghai Tianma Radio Telescope (TMRT). The sample consists of 3348 sources selected from the all-sky Wide-field Infrared Survey Explorer (WISE) point-source catalog. We discussed the selection criteria in detail and the detection results of those at high Galactic latitudes (i.e., |b|>2{deg}) in a previous paper (Paper I; Yang+ 2017, J/ApJ/846/160). Here, we present the results from the survey of those at low Galactic latitudes, i.e., |b|<2{deg}. Of 1875 selected WISE point sources, 291 positions that were actually associated with 224 sources that were detected with CH_3_OH maser emission. Among them, 32 are newly detected. A majority of the newly detected sources are associated with bright WISE sources. The majority of the detected sources (209/224=93.3%) are quite close to the Galactic Plane (|b|<1{deg}) and lie on the inner spiral arms with positive local standard of rest velocities. The detection rate and the color-color distribution of our detection are all matched with our anticipation. Combining with detections from previous surveys, we compile a catalog of 1085 sources with 6.7GHz CH_3_OH maser emission in our Galaxy.
« Previous |
1 - 10 of 29
|
Next »
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AZh/72/22
- Title:
- A 95 GHz Survey of Methanol Masers
- Short Name:
- J/AZh/72/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A 95GHz survey of methanol emission in the 8_0_-7_1_A^+^ transition was conducted with the 20-m radio telescope at Onsala. Twenty-six new sources were detected in the emission line. At least nine out of the 35 studied sources are masers.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/187
- Title:
- ALMA and VLA radio continuum obs. of NGC 6334I
- Short Name:
- J/ApJ/832/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Very Large Array and Atacama Large Millimeter/submillimeter Array imaging of the deeply embedded protostellar cluster NGC 6334I from 5cm to 1.3mm at angular resolutions as fine as 0.17" (220au). The dominant hot core MM1 is resolved into seven components at 1.3mm, clustered within a radius of 1000au. Four of the components have brightness temperatures >200K, radii ~300au, minimum luminosities ~10^4^L_{sun}_, and must be centrally heated. We term this new phenomenon a "hot multi-core." Two of these objects also exhibit compact free-free emission at longer wavelengths, consistent with a hypercompact HII region (MM1B) and a jet (MM1D). The spatial kinematics of the water maser emission centered on MM1D are consistent with it being the origin of the high-velocity bipolar molecular outflow seen in CO. The close proximity of MM1B and MM1D (440au) suggests a proto-binary or a transient bound system. Several components of MM1 exhibit steep millimeter spectral energy distributions indicative of either unusual dust spectral properties or time variability. In addition to resolving MM1 and the other hot core (MM2) into multiple components, we detect five new millimeter and two new centimeter sources. Water masers are detected for the first time toward MM4A, confirming its membership in the protocluster. With a 1.3mm brightness temperature of 97K coupled with a lack of thermal molecular line emission, MM4A appears to be a highly optically thick 240L_{sun}_ dust core, possibly tracing a transient stage of massive protostellar evolution. The nature of the strongest water maser source CM2 remains unclear due to its combination of non-thermal radio continuum and lack of dust emission.
- ID:
- ivo://CDS.VizieR/J/AJ/152/92
- Title:
- Ammonia and CO outflow around 6.7GHz methanol masers
- Short Name:
- J/AJ/152/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Single point observations are presented in NH_3_ (1, 1) and (2, 2) inversion transitions using the Effelsberg 100m telescope for a sample of 100 6.7GHz methanol masers and mapping observations in the ^12^CO and ^13^CO (1-0) transitions using the Purple Mountain Observatory Delingha 13.7m telescope for 82 sample sources with detected ammonia. A further 62 sources were selected for either ^12^CO or ^13^CO line outflow identification, producing 45 outflow candidates, 29 using ^12^CO and 16 using ^13^CO data. Twenty-two of the outflow candidates were newly identified, and 23 had trigonometric parallax distances. Physical properties were derived from ammonia lines and CO outflow parameters were calculated. Histograms and statistical correlations for ammonia, CO outflow parameters, and 6.7GHz methanol maser luminosities are also presented. No significant correlation was found between ammonia and maser luminosity. However, weak correlations were found between outflow properties and maser luminosities, which may indicate that outflows are physically associated with 6.7GHz masers.
- ID:
- ivo://CDS.VizieR/J/ApJ/822/59
- Title:
- BGPS. XIV. Molecular cloud clumps GBT obs.
- Short Name:
- J/ApJ/822/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We sort 4683 molecular clouds between 10{deg}<l<65{deg} from the Bolocam Galactic Plane Survey based on observational diagnostics of star formation activity: compact 70{mu}m sources, mid-IR color-selected YSOs, H_2_O and CH_3_OH masers, and UCHII regions. We also present a combined NH_3_-derived gas kinetic temperature and H_2_O maser catalog for 1788 clumps from our own GBT 100m observations and from the literature. We identify a subsample of 2223 (47.5%) starless clump candidates (SCCs), the largest and most robust sample identified from a blind survey to date. Distributions of flux density, flux concentration, solid angle, kinetic temperature, column density, radius, and mass show strong (>1dex) progressions when sorted by star formation indicator. The median SCC is marginally subvirial ({alpha}~0.7) with >75% of clumps with known distance being gravitationally bound ({alpha}<2). These samples show a statistically significant increase in the median clump mass of {Delta}M~170-370M_{sun}_ from the starless candidates to clumps associated with protostars. This trend could be due to (i) mass growth of the clumps at dM/dt~200-440M_{sun}_/Myr for an average freefall 0.8Myr timescale, (ii) a systematic factor of two increase in dust opacity from starless to protostellar phases, and/or (iii) a variation in the ratio of starless to protostellar clump lifetime that scales as ~M^-0.4^. By comparing to the observed number of CH_3_OH maser containing clumps, we estimate the phase lifetime of massive (M>10^3^M_{sun}_) starless clumps to be 0.37+/-0.08Myr (M/10^3^M_{sun}_)^-1^; the majority (M<450M_{sun}_) have phase lifetimes longer than their average freefall time.
- ID:
- ivo://CDS.VizieR/J/ApJS/227/10
- Title:
- CH_3_OH & OH line emission from Galactic center
- Short Name:
- J/ApJS/227/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Class I methanol masers are collisionally pumped and are generally correlated with outflows in star-forming sites in the Galaxy. Using the Very Large Array in its A-array configuration, we present a spectral line survey to identify methanol J=4_-1_->3_0_E emission at 36.169GHz. Over 900 pointings were used to cover a region 66'x13' along the inner Galactic plane. A shallow survey of OH at 1612, 1665, 1667, and 1720MHz was also carried out over the area covered by our methanol survey. We provide a catalog of 2240 methanol masers with narrow line-widths of ~1km/s, spatial resolutions of ~0.14"x0.05", and rms noises ~20mJy/beam per channel. Lower limits on the brightness temperature range from 27000 to 10000000K, showing that the emission is of non-thermal origin. We also provide a list of 23 OH (1612), 14 OH (1665), 5 OH (1667), and 5 OH (1720MHz) masers. The origin of such a large number of methanol masers is not clear. Many methanol masers appear to be associated with infrared dark clouds, though it appears unlikely that the entire population of these masers traces the early phase of star formation in the Galactic center.
- ID:
- ivo://CDS.VizieR/J/ApJS/160/220
- Title:
- Full-polarization observations of OH masers
- Short Name:
- J/ApJS/160/220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present full-polarization VLBA maps of the ground-state, main-line, ^2^{Pi}_3/2_, J=3/2 OH masers in 18 Galactic massive star-forming regions. This is the first large polarization survey of interstellar hydroxyl masers at VLBI resolution. A total of 184 Zeeman pairs are identified, and the corresponding magnetic field strengths are indicated. We also present spectra of the NH_3_ emission or absorption in these star-forming regions.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A142
- Title:
- G24.78+0.08 A1 ALMA images and datacubes
- Short Name:
- J/A+A/650/A142
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Hyper-compact (HC) or ultra-compact HII regions are the first manifestations of the radiation feedback from a newly born massive star. Therefore, their study is fundamental to understanding the process of massive (>=8M_{sun}_) star formation. We employed Atacama Large Millimeter/submillimeter Array (ALMA) 1.4mm Cycle 6 observations to investigate at high angular resolution (~0.050, corresponding to 330au) the HC HII region inside molecular core A1 of the high-mass star-forming cluster G24.78+0.08. We used the H30{alpha} emission and different molecular lines of CH_3_CN and ^13^CH_3_CN to study the kinematics of the ionized and molecular gas, respectively. At the center of the HC HII region, at radii <~500au, we observe two mutually perpendicular velocity gradients, which are directed along the axes at PA=39{deg} and PA=133{deg}, respectively. The velocity gradient directed along the axis at PA=39{deg} has an amplitude of 22km/s/mpc, which is much larger than the other;s, 3km/s/mpc. We interpret these velocity gradients as rotation around, and expansion along, the axis at PA=39{deg}. We propose a scenario where the H30{alpha} line traces the ionized heart of a disk-jet system that drives the formation of the massive star (~20M_{sun}_) responsible for the HC HII region. Such a scenario is also supported by the position-velocity plots of the CH_3_CN and ^13^CH_3_CN lines along the axis at PA=133{deg}, which are consistent with Keplerian rotation around a 20M_{sun}_ star. Toward the HC HII region in G24.78+0.08, the coexistence of mass infall (at radii of ~5000au), an outer molecular disk (from <~4000 au to >~500au), and an inner ionized disk (<~500au) indicates that the massive ionizing star is still actively accreting from its parental molecular core. To our knowledge, this is the first example of a molecular disk around a high-mass forming star that, while becoming internally ionized after the onset of the HII region, continues to accrete mass onto the ionizing star.
- ID:
- ivo://CDS.VizieR/J/A+A/432/737
- Title:
- General Catalogue of 6.7GHz Methanol Masers
- Short Name:
- J/A+A/432/737
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Methanol masers are often detected in regions of intense star formation. Several studies in the last decade indicate that they may even be the earliest signpost of a high-mass star-forming region. Their powerful emission makes them very good candidates for observations using both single-dish telescopes and interferometers, the latter allows detailed structural and dynamical study of these objects. We present here a catalogue of all known 6.7GHz methanol masers, discovered both by surveys that targeted possible associated objects and unbiased surveys covering a large fraction of galactic longitudes across the Galactic plane 0.5{deg}<=b<=0.5deg} for most of the regions). The 519 sources which are listed with their kinematic (galactocentric and heliocentric) distance as well as possibly associated IR objects. We find that 6.7GHz methanol masers clearly trace the molecular ring of our Galaxy, where most of the OB associations are located. The present list of masers also reports detections of other masing transitions of methanol as further information for the study of the maser phenomenon. In a further publication we will address some statistical considerations.
- ID:
- ivo://CDS.VizieR/J/ApJS/200/5
- Title:
- 95GHz class I methanol maser survey
- Short Name:
- J/ApJS/200/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a survey with the Purple Mountain Observatory 13.7m radio telescope for class I methanol masers from the 95GHz (8_0_-7_1_A^+^) transition. Two hundred and fourteen target sources were selected by combining information from both the Spitzer GLIMPSE and 1.1mm Bolocam Galactic Plane Survey (BGPS) catalogs. The observed sources satisfy the GLIMPSE mid-IR criteria of [3.6]-[4.5]>1.3, [3.6]-[5.8]>2.5, [3.6]-[8.0]>2.5 and 8.0um mag less than 10; they also have an associated 1.1mm BGPS source. Class I methanol maser emission was detected in 63 sources, corresponding to a detection rate of 29% for this survey. For the majority of detections (43), this is the first identification of class I methanol masers associated with these sources. We show that the intensity of the class I methanol maser emission is not closely related to mid-IR intensity or the colors of the GLIMPSE point sources; however, it is closely correlated with properties (mass and beam-averaged column density) of the BGPS sources. Comparison of measures of star formation activity for the BGPS sources with and without class I methanol masers indicates that the sources with class I methanol masers usually have higher column density and larger flux density than those without them.
- « Previous
- Next »
- 1
- 2
- 3
