- ID:
- ivo://CDS.VizieR/J/A+AS/101/153
- Title:
- Galactic H2O masers
- Short Name:
- J/A+AS/101/153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The association between galactic H2O masers and IRAS sources from the Point Source Catalog (Cat. II/125) is established for 442 sources out of a list of 505 objects, which includes all the galactic H2O masers north of 30{deg}, known up to 1988. Using a multivariate statistical analysis on the four far-IR fluxes of the associated IRAS source, galactic H2O masers are reclassified into two classes: those associated to star forming regions (SFR, 52%) and those associated to late type stars (STAR, 45%). The remaining 3% cannot be included in either class. The present classification is compared with others in the literature. Distances for a large subsample of 1120 masers are derived, using the galactic rotation curve for SFR and literature data for STAR.The parameters of the H2O maser emission (e.g. integrated flux, luminosity, variability), collected in a homogeneous way in the Arcetri H2O atlas (Comoretto et al. 1990A&AS...84..179C), and those of the associated IRAS sources (e.g. flux density, luminosity, colours) are used to investigate, in a statistical way, the properties of the STAR and SFR classes. In particular, we investigate the spatial distribution of masers both in the galactic plane and perpendicular to it. We also compare the H2O and IRAS luminosities, finding a good correlation. Moreover, we find that high luminosity sources show low colour temperatures and vice versa. The spectral profile and variability are then investigated by different means. Finally, the luminosity function for each maser class is derived.
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Search Results
- ID:
- ivo://CDS.VizieR/J/PAZh/37/281
- Title:
- Galactic rotation curve from selected maser
- Short Name:
- J/PAZh/37/281
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on currently available observations of 28 maser sources in 25 star-forming regions with measured trigonometric parallaxes, proper motions, and radial velocities, we have constructed the rotation curve of the Galaxy. Taking different distances to the Galactic center R_0_, we have estimated the peculiar velocity of the Sun, the angular velocity of Galactic rotation, and its three derivatives.
- 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/A+A/616/A66
- Title:
- 6.7GHz CH_3_OH maser in G24.78+0.08
- Short Name:
- J/A+A/616/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- G24.78+0.08 is a well known high-mass star-forming region, where several molecular cores harboring OB young stellar objects are found inside a clump of size ~=1pc. This article focuses on the most prominent of these cores, A1, where an intense hypercompact (HC) HII region has been discovered by previous observations. Our aim is to determine the physical conditions and the kinematics of core A1, and study the interaction of the HII region with the parental molecular core. We combine ALMA 1.4mm high-angular resolution (~=0.2'') observations of continuum and line emission with multi-epoch Very Long Baseline Interferometry data of water 22GHz and methanol 6.7GHz masers. These observations allow us to study the gas kinematics on linear scales from 10 to 10^4^au, and to accurately map the physical conditions of the gas over core A1. The 1.4mm continuum is dominated by free-free emission from the intense HC HII region (size~=1000au) observed to the North of core A1 (region A1N). Analyzing the H30{alpha} line, we reveal a fast bipolar flow in the ionized gas, covering a range of LSR velocities (VLSR) of ~=60km/s. The amplitude of the VLSR gradient, 22km/s/mpc, is one of the highest so far observed towards HC HII regions. Water and methanol masers are distributed around the HC HII region in A1N, and the maser three-dimensional (3D) velocities clearly indicate that the ionized gas is expanding at high speed (>=200km/s) into the surrounding molecular gas. The temperature distribution (in the range 100-400K) over core A1, traced with molecular (CH_3_OCHO, ^13^CH_3_CN, ^13^CH_3_OH, and CH_3_CH_2_CN) transitions with level energy in the range 30K<=E_u_/k<=300K, reflects the distribution of shocks produced by the fast-expansion of the ionized gas of the HII region. The high-energy (550K<=E_u_/k<=800K) transitions of vibrationally excited CH_3_CN are likely radiatively pumped, and their rotational temperature can significantly differ from the kinetic temperature of the gas. Over core A1, the VLSR maps from both the 1.4mm molecular lines and the 6.7GHz methanol masers consistently show a VLSR gradient (amplitude ~=0.3km/s/mpc) directed approximately S-N. Rather than gravitationally supported rotation of a massive toroid, we interpret this velocity gradient as a relatively slow expansion of core A1.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/160
- Title:
- 6.7GHz Class II methanol maser survey
- Short Name:
- J/ApJ/846/160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a systematic 6.7GHz Class II methanol maser survey using the Shanghai Tianma Radio Telescope toward targets selected from the all-sky Wide-Field Infrared Survey Explorer (WISE) point catalog. In this paper, we report the results from the survey of those at high Galactic latitudes, i.e., |b|>2{deg}. Of 1473 selected WISE point sources at high latitude, 17 point positions that were actually associated with 12 sources were detected with maser emission, reflecting the rarity (1%-2%) of methanol masers in the region away from the Galactic plane. Out of the 12 sources, 3 are detected for the first time. The spectral energy distribution at infrared bands shows that these new detected masers occur in the massive star-forming regions. Compared to previous detections, the methanol maser changes significantly in both spectral profiles and flux densities. The infrared WISE images show that almost all of these masers are located in the positions of the bright WISE point sources. Compared to the methanol masers at the Galactic plane, these high-latitude methanol masers provide good tracers for investigating the physics and kinematics around massive young stellar objects, because they are believed to be less affected by the surrounding cluster environment.
- 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.
- 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.
- 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.
