VLBI Water Maser Proper Motion Measurements in Star-Forming Regions

2005 ◽  
pp. 53-63
Author(s):  
J.M. Torrelles ◽  
N. Patel ◽  
J.F. Gómez ◽  
G. Anglada ◽  
L. Uscanga
Keyword(s):  
Proper Motion ◽  
Star Forming ◽  
Star Forming Regions ◽  
Motion Measurements ◽  
Water Maser

Vlbi Water Maser Proper Motion Measurements in Star-Forming Regions

2005 ◽  
Vol 295 (1-2) ◽  
pp. 53-63 ◽  
Author(s):  
J. M. Torrelles ◽  
N. Patel ◽  
J. F. G�mez ◽  
G. Anglada ◽  
L. Uscanga
Keyword(s):  
Proper Motion ◽  
Star Forming ◽  
Star Forming Regions ◽  
Motion Measurements ◽  
Water Maser

scholarly journals Masers as probes of proto-planetary discs

2004 ◽  
Vol 202 ◽  
pp. 362-364
Author(s):  
A.M.S. Richards ◽  
R. J. Cohen ◽  
M. Crocker ◽  
E. E. Lekht ◽  
V. Samodourov ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Radio Telescope ◽  
Keplerian Orbit ◽  
Proper Motions ◽  
Central Mass ◽  
Maser Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
Velocity Variations ◽  
Water Maser

Water maser emission from star forming regions has been monitored for several decades using the Puschino radio telescope, showing radial velocity variations consistent with material in Keplerian orbit around protostars. MERLIN and the EVN are now being used to image the 22 GHz emission on au scales and measure proper motions. This will distinguish discs from outflows, and provide an estimate of the central mass and possibly orbiting condensations.

scholarly journals 22 GHz Water Maser Survey of the Xinjiang Astronomical Observatory

2012 ◽  
Vol 8 (S287) ◽  
pp. 296-297
Author(s):  
Jian-jun Zhou ◽  
Jarken Esimbek ◽  
Gang Wu
Keyword(s):  
Galactic Plane ◽  
Astronomical Observatory ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Gas Kinematics ◽  
Star Forming Regions ◽  
Water Masers ◽  
Maser Sources ◽  
Water Maser

AbstractWater masers are good tracers of high-mass star-forming regions. Water maser VLBI observations provide a good probe for studying high-mass star formation and galactic structure. We plan to make a blind survey toward the northern Galactic plane in future years using the 25 m radio telescope of the Xinjiang Astronomical Observatory. We will select some water maser sources discovered in the survey and perform high resolution observations to study the gas kinematics close to high-mass protostars.

scholarly journals RadioAstron space-VLBI project: studies of masers in star forming regions of our Galaxy and megamasers in external galaxies

2017 ◽  
Vol 13 (S336) ◽  
pp. 417-421 ◽  
Author(s):  
A. M. Sobolev ◽  
N. N. Shakhvorostova ◽  
A. V. Alakoz ◽  
W. A. Baan
Keyword(s):  
Angular Resolution ◽  
Nearby Galaxy ◽  
Major Step ◽  
Maser Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Galaxy ◽  
External Galaxies ◽  
First Time ◽  
Water Maser

AbstractObservations of the masers in the course of RadioAstron mission yielded detections of fringes for a number of sources in both water and hydroxyl maser transitions. Several sources display numerous ultra-compact details. This proves that implementation of the space VLBI technique for maser studies is possible technically and is not always prevented by the interstellar scattering, maser beaming and other effects related to formation, transfer, and detection of the cosmic maser emission. For the first time, cosmic water maser emission was detected with projected baselines exceeding Earth Diameter. It was detected in a number of star-forming regions in the Galaxy and two megamaser galaxies NGC 4258 and NGC 3079. RadioAstron observations provided the absolute record of the angular resolution in astronomy. Fringes from the NGC 4258 megamaser were detected on baseline exceeding 25 Earth Diameters. This means that the angular resolution sufficient to measure the parallax of the water maser source in the nearby galaxy LMC was directly achieved in the cosmic maser observations. Very compact features with angular sizes about 20\muas\, have been detected in star-forming regions of our Galaxy. Corresponding linear sizes are about 5-10 million kilometers. So, the major step from milli- to micro-arcsecond resolution in maser studies is achieved by the RadioAstron mission. The existence of the features with extremely small angular sizes is established. Further implementations of the space–VLBI maser instrument for studies of the nature of cosmic objects, studies of the interaction of extremely high radiation field with molecular material and studies of the matter on the line of sight are planned.

scholarly journals Proper motions of water masers: W 51 North, Main, and South

2002 ◽  
Vol 206 ◽  
pp. 88-91 ◽  
Author(s):  
Hiroshi Imai ◽  
Tetsuo Sasao ◽  
Osamu Kameya ◽  
Teruhiko Watanabe ◽  
Toshihiro Omodaka ◽  
...  
Keyword(s):  
Proper Motion ◽  
Massive Star ◽  
Model Fitting ◽  
Proper Motions ◽  
Star Forming ◽  
Motion Measurements ◽  
Water Masers ◽  
Reference Feature

We describe the proper motion measurements of water masers in the massive-star forming region W 51A and the analysis of the 3-D kinematics in three maser clusters of W 51A. We found a systematic expanding motion in one of the clusters named W 51 North, while no systematic motion was detected in other two clusters named W 51 Main and South. The 3-D motions of the clusters relative to the position reference feature in W 51 North indicate a separating motion between the W 51 North and the W 51 Main/South clusters. We estimated the distance to W 51 North as to be 6.7±2.1 kpc on basis of the statistical parallax and the model fitting methods.

scholarly journals A 20-year H2O maser monitoring program with the Medicina 32-m telescope

2007 ◽  
Vol 3 (S242) ◽  
pp. 223-227 ◽  
Author(s):  
J. Brand ◽  
M. Felli ◽  
R. Cesaroni ◽  
C. Codella ◽  
G. Comoretto ◽  
...  
Keyword(s):  
Sampling Rate ◽  
Monitoring Program ◽  
Late Type ◽  
Maser Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
Vlbi Observations ◽  
Water Maser ◽  
Representative Samples

AbstractThe Arcetri/Bologna H2O maser group has been monitoring the 1.3-cm water maser emission from a sample of 43 star-forming regions (SFRs) and 22 late-type stars for about 20 years at a sampling rate of 4-5 observations each year, using the 32-m Medicina Radio Telescope (HPBW 1.′9 at 22 GHz). For the late-type stars we observe representative samples of OH/IR-stars, Mira's, semi-regular variables, and supergiants. The SFR-sample spans a large interval in FIR luminosity of the associated Young Stellar Object (YSO), from 20 L⊙ to 1.5 × 106 L⊙, and offers a unique data base for the study of the long-term (years) variability of the maser emission in regions of star formation.This presentation concerns only the masers in SFRs. The information obtained from single-dish monitoring is complementary to what is extracted from higher-resolution (VLA and VLBI) observations, and can better explore the velocity domain and the long-term variability therein.We characterize the variability of the sources in various ways and we study how it depends on the luminosity and other properties of the associated YSO and its environment.

scholarly journals VLBI multi-epoch water maser observations toward massive protostars

2012 ◽  
Vol 8 (S287) ◽  
pp. 377-385 ◽  
Author(s):  
José M. Torrelles ◽  
José F. Gómez ◽  
Nimesh A. Patel ◽  
Salvador Curiel ◽  
Guillem Anglada ◽  
...  
Keyword(s):  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Central Engine ◽  
Dynamic Scenario ◽  
Low Mass ◽  
Cepheus A ◽  
Water Maser

AbstractVLBI multi-epoch water maser observations are a powerful tool to study the gas very close to the central engine responsible for the phenomena associated with the early evolution of massive protostars. In this paper we present a summary of the main observational results obtained toward the massive star-forming regions of Cepheus A and W75N. These observations revealed unexpected phenomena in the earliest stages of evolution of massive objects (e.g., non-collimated “short-lived” pulsed ejections in different massive protostars), and provided new insights in the study of the dynamic scenario of the formation of high-mass stars (e.g., simultaneous presence of a jet and wide-angle outflow in the massive object Cep A HW2, similar to what is observed in low-mass protostars). In addition, with these observations it has been possible to identify new, previously unseen centers of high-mass star formation through outflow activity.

scholarly journals Observations of water maser sources at Arcetri

2002 ◽  
Vol 206 ◽  
pp. 39-42
Author(s):  
Giovanni Comoretto ◽  
Riccardo Valdettaro ◽  
Francesco Palla ◽  
Jan Brand ◽  
Riccardo Cesaroni ◽  
...  
Keyword(s):  
Time Variability ◽  
Star Forming ◽  
Star Forming Regions ◽  
Global Properties ◽  
Spectral Components ◽  
Water Masers ◽  
Variability Study ◽  
Maser Sources ◽  
Water Maser ◽  
Nominal Position

We present the current activity of the Arcetri group in the field of water masers. This is mainly represented by observations with the Medicina radiotelescope, whose main outcome has been the compilation of the Arcetri Catalog and the study of time variability of selected sources. The Arcetri Catalog update reports the results of the observations carried out from January 1993 to April 2000 on a sample of 300 sources. The global properties of the complete Arcetri Catalog (including Comoretto et al. 1990, and Brand et al. 1994) are discussed. Of the 1013 sources, 937 have an IRAS counterpart within 1 arcmin from the nominal position of the maser. We establish a classification scheme based on the IRAS flux densities which allows to distinguish between water masers associated with star forming regions and late-type stars. The time variability study shows a large variety of behaviors. Generally more luminous sources present less variable emission and spectral components over a wider velocity range.

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