Results for "K. M. Menten"

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Perspective from a Younger Generation -- The Astro-Spectroscopy of Gisbert WinnewisserFeb 01 2004Gisbert Winnewisser's astronomical career was practically coextensive with the whole development of molecular radio astronomy. Here I would like to pick out a few of his many contributions, which I, personally, find particularly interesting and put them ... More
SiO maser emission from red supergiants across the Galaxy: I. Targets in massive star clustersMar 21 2012Apr 03 2012Aims. Red supergiants (RSGs) are among the most luminous of all stars, easily detectable in external galaxies, and may ideally serve as kinematic tracers of Galactic structure. Some RSGs are surrounded by circumstellar envelopes detectable by their dust ... More
Initial Conditions for Massive Star Birth -- Infrared Dark CloudsAug 01 2005Aug 02 2005We summarize the properties of Infrared Dark Clouds, massive, dense, and cool aggregations of interstellar gas and dust that are found througout the Galaxy in projection against the strong mid-infrared background. We describe their distribution and give ... More
Molecular QSO Absorption Line SystemsOct 15 2000We review observations of molecular absorption line systems at high redshift toward red quasars and gravitational lenses.
Discovery of a parsec-scale bipolar nebula around MWC 349AMar 13 2012We report the discovery of a bipolar nebula around the peculiar emission-line star MWC 349A using archival Spitzer Space Telescope 24 um data. The nebula extends over several arcminutes (up to 5 pc) and has the same orientation and geometry as the well-known ... More
Probing the fast outflow in IRAS 15452-5459 with ATCA observations of OH, H2O, and SiO masersJun 07 2013Maser lines of OH, H2 O, and SiO are commonly observed in O-rich AGB stars, but their presence after the end of the Asymptotic Giant Branch (AGB) phase is linked to non-spherical mass-loss processes. IRAS 15452-5459 is a post-AGB star with an hourglass ... More
CO observations of water-maser post-AGB stars and detection of a high-velocity outflow in IRAS 15452-5459Mar 22 2012Many aspects of the evolutionary phase in which Asymptotic Giant Branch stars (AGB stars) are in transition to become Planetary Nebulae (PNe) are still poorly understood. An important question is how the circumstellar envelopes of AGB stars switch from ... More
The cometary HII regions of DR 21: Bow shocks or champagne flows or both?Jan 07 2014We present deep Very Large Array H66$\alpha$ radio recombination line (RRL) observations of the two cometary HII regions in DR 21. With these sensitive data, we test the "hybrid" bow shock/champagne flow model previously proposed for the DR 21 HII regions. ... More
Trigonometric Parallax of W51 Main/SouthJun 22 2010Aug 04 2010We report measurement of the trigonometric parallax of W51 Main/South using the Very Long Baseline Array (VLBA). We measure a value of 0.185 +/- 0.010 mas, corresponding to a distance of 5.41 (+0.31/-0.28) kpc. W51 Main/South is a well-known massive star-forming ... More
Resolving the extended atmosphere and the inner wind of Mira ($o$ Ceti) with long ALMA baselinesMar 10 2016The prototypical Mira variable, $o$ Cet (Mira), has been observed as a Science Verification target in the 2014 ALMA Long Baseline Campaign with a longest baseline of 15 km. ALMA clearly resolves the images of the continuum and molecular line emission/absorption ... More
The evolutionary tracks of young massive star clustersAug 26 2014Stars mostly form in groups consisting of a few dozen to several ten thousand members. For 30 years, theoretical models provide a basic concept of how such star clusters form and develop: they originate from the gas and dust of collapsing molecular clouds. ... More
Recent star formation in the inner Galactic Bulge seen by ISOGAL II -- The Central Molecular ZoneNov 14 2011We present 5--38 $\mu$m spectroscopic observations of a sample of 68 ISOGAL sources with unknown natures, taken with the Spitzer Infrared Spectrograph. Based on the characteristics and the slope of their spectra we classified the sources as young or late-type ... More
A multi-wavelength view of the Galactic center dust ridge reveals little star formationNov 02 2012The Galactic center dust ridge consists of a narrow string of massive condensations identified in submillimeter dust continuum emission. To determine whether new high-mass stars are forming in this region, we performed new observations at 870 $\mu$m with ... More
New Measurements of the Radio Photosphere of Mira based on Data from the JVLA and ALMAJun 09 2015We present new measurements of the millimeter wavelength continuum emission from the long period variable Mira ($o$ Ceti) at frequencies of 46 GHz, 96 GHz, and 229 GHz ($\lambda$~7 mm, 3 mm, and 1 mm) based on observations obtained with the Jansky Very ... More
Physical characteristics of bright Class I methanol masersMay 30 2016Class I CH$_3$OH masers trace interstellar shocks. They have received little attention mostly as a consequence of their low luminosities; this situation has changed recently and Class I masers are now routinely used as signposts of outflows. The recent ... More
A Class of Interstellar OH Masers Associated with Protostellar OutflowsApr 30 2003Using the Very Large Array, we have detected weak OH maser emission near the Turner-Welch protostellar source in the W3 OH region. Unlike typical interstellar OH masers, which are associated with ultra-compact HII regions, our measured positions and proper ... More
The distance to the Orion NebulaSep 04 2007We have used the Very Long Baseline Array to measure the trigonometric parallax of several member stars of the Orion Nebula Cluster showing non-thermal radio emission. We have determined the distance to the cluster to be 414 +/- 7 pc. Our distance determination ... More
Discovery of a luminous water megamaser in the FRII radiogalaxy 3C403Jul 03 2003We report the first detection of a water megamaser in a radio-loud galaxy, 3C403. This object has been observed as part of a small sample of FRIIs with evidence of nuclear obscuration. The isotropic luminosity of the maser is ~1200 L(sun). With a recessional ... More
Aluminium oxide in the optical spectrum of VY Canis MajorisNov 17 2012We report the first identification of the optical bands of the B-X system of AlO in the red supergiant VY CMa. In addition to TiO, VO, ScO, and YO, which were recognized in the optical spectrum of the star long time ago, AlO is another refractory molecule ... More
Size determination of the Centaur Chariklo from millimeter-wavelength bolometer observationsDec 16 2000Using the Max-Planck Millimeter Bolometer Array (MAMBO) at the IRAM 30m telescope we detected emission at 250 GHz from the Centaur Chariklo (1997 CU26). The observed continuum flux density implies a photometric diameter of 273 km. The resulting geometric ... More
The water megamaser in the merger system Arp299Oct 30 2006We present preliminary results of an interferometric study of the water megamaser in the merger system Arp299. This system is composed of two main sources: IC694 and NGC3690. There is clear evidence that most of the water maser emission is associated ... More
APEX telescope observations of new molecular ionsFeb 14 2011Hydrides are key ingredients of interstellar chemistry since they are the initial products of chemical networks that lead to the formation of more complex molecules. The fundamental rotational transitions of light hydrides fall into the submillimeter ... More
VLBA Observations and Effelsberg Monitoring of a Flaring Water Maser in Mrk 348Jul 09 2001We report on single-dish monitoring as well as extremely high angular resolution observations of the flaring H2O maser in the Seyfert 2 galaxy Mrk 348. The H2O line is redshifted by ~130 km/s with respect to the systemic velocity, is very broad, with ... More
Water maser emission in IC342Jan 28 2002The detection of 22 GHz water vapor emission from IC342 is reported, raising the detection rate among northern galaxies with 100 micron IRAS point source fluxes > 50 Jy to 16%. The maser, associated with a star forming region 10-15 arcsec west of the ... More
The association between water kilomasers and compact radio sources in the starburst galaxy NGC2146May 16 2002We report the detection of 22 GHz water vapor emission toward the starburst galaxy NGC2146, made using the Effelsberg 100-m telescope. Interferometric observations with the Very Large Array (VLA) show that a part of the emission originates from two prominent ... More
Accurate rest frequencies of methanol maser and dark cloud linesAug 04 2004Dec 01 2004We report accurate laboratory measurements of selected methanol transition frequencies between 0.834 and 230 GHz in order to facilitate astronomical velocity analyses. New data have been obtained between 10 and 27 GHz and between 60 and 119 GHz. Emphasis ... More
Physical conditions around 6.7 GHz methanol masers-I: AmmoniaJun 01 2012Methanol masers at 6.7 GHz are known to be tracers of high-mass star formation in our Galaxy. In this paper, we study the large scale physical conditions in the star forming clumps/cores associated with 6.7 GHz methanol masers using observations of the ... More
First interstellar detection of OH+Apr 15 2010May 27 2010The Atacama Pathfinder Experiment (APEX) 12m telescope was used to observe the N=1-0, J=0-1 ground state transitions of OH+ at 909.1588 GHz with the CHAMP+ heterodyne array receiver. Two blended hyperfine structure transitions were detected in absorption ... More
Mid- and high-J CO observations towards UCHIIsMay 26 2006A study of 12 ultracompact HII regions was conducted to probe the physical conditions and kinematics in the inner envelopes of the molecular clumps harboring them. The APEX telescope was used to observe the sources in the CO (4-3) and 13CO (8-7) lines. ... More
The Arecibo Methanol Maser Galactic Plane Survey - III: Distances and LuminositiesOct 20 2009We derive kinematic distances to the 86 6.7 GHz methanol masers discovered in the Arecibo Methanol Maser Galactic Plane Survey. The systemic velocities of the sources were derived from 13CO (J=2-1), CS (J=5-4), and NH3 observations made with the ARO Submillimeter ... More
New water masers in Seyfert and FIR bright galaxies. IIDec 05 2007Recently, a relationship between the water maser detection rate and far infrared (FIR) flux density has been found as a result of a 22 GHz maser survey in a sample comprised of northern galaxies with 100 micron flux density > 50 Jy and a declination >-30 ... More
The kinetic temperature of a molecular cloud at redshift 0.9: Ammonia in the gravitational lens PKS1830-211Aug 11 2008Using the Green Bank Telescope (GBT), we have detected the (J,K) = (1,1) to (10,10) ammonia inversion lines, up to 1030 K above the ground state, in a face-on spiral galaxy viewed against the radio continuum of the lensed background source PKS 1830-211. ... More
Parsec-Scale Imaging of HI Absorption in 1946+708Sep 22 2000In the last several years, a number of compact extragalactic radio sources have been found to exhibit neutral hydrogen absorption at or near the systemic velocities of their host galaxies. Models proposed to explain this phenomenon involve a circumnuclear ... More
Water vapor in the starburst galaxy NGC 253: A new nuclear maser?Oct 20 200322 GHz water vapor emission was observed toward the central region of the spiral starburst galaxy NGC 253. Monitoring observations with the 100-m telescope at Effelsberg and measurements with the BnC array of the VLA reveal three distinct velocity components, ... More
The dynamical state of the First Hydrostatic Core Candidate Cha-MMS1Jun 27 2013Observations of First Hydrostatic Core candidates, a theoretically predicted evolutionary link between the prestellar and protostellar phases, are vital for probing the earliest phases of star formation. We aim to determine the dynamical state of the ... More
Very compact radio emission from high-mass protostars. I. CRL 2136: Continuum and water maser observationsOct 22 2003Dec 15 2003We report 5-43 GHz radio observations of the CRL 2136 region at 0.6-6 arcsec resolution. We detect weak (mJy intensity) radio emission from the deeply embedded high-mass protostar IRS 1, which has an optically thick spectrum up to frequencies of 22 GHz, ... More
Widespread HCN maser emission in carbon-rich evolved starsMar 02 2018Context. HCN is a major constituent of the circumstellar envelopes of carbon-rich evolved stars, and rotational lines from within its vibrationally excited states probe parts of these regions closest to the stellar surface. A number of such lines are ... More
Z-machine science other than CO - scientific and technical prospects for very wide band-width radio and (sub)millimeter-wavelength spectroscopyMar 23 2006While clearly the main scientific targets of ''z-machines" will be redshifted lines of carbon monoxide, there also exist other interesting applications. Here scientific and technological aspects of observing lines from CO and other species at high redshift ... More
IAU (Maser) Symposium 287 SummaryApr 26 2012Apr 27 2012I'm trying to summarize the science communicated via oral presentations and by posters at the IAU Symposium 287 "Cosmic Masers - from OH to H_0", which took place from January 29 to February 3, 2012 in Stellenbosch, South Africa.
Exciting Maser Science with New Instruments - the Promise of the EVLAAug 22 2007Aug 28 2007In the near future, the Expanded Very Large Array (EVLA) will allow surveys for maser sources with unprecedented sensitivity, spectral coverage and spectroscopic capabilities. In particular, comprehensive surveys for many maser species with simultaneous ... More
Trigonometric Parallaxes of Massive Star Forming Regions: G012.88+0.48 and W33Apr 07 2013We report trigonometric parallaxes for water masers in the G012.88+0.48 region and in the massive star forming complex W33 (containing G012.68--0.18, G012.81--0.19, G012.90--0.24, G012.90--0.26), from the Bar and Spiral Structure Legacy (BeSSeL) survey ... More
IRAS 05358+3543: Multiple outflows at the earliest stages of massive star formationMar 01 2002We present a high-angular-resolution molecular line and millimeter continuum study of the massive star formation site IRAS 05358+3543. The most remarkable feature is a highly collimated (collimation factor ~10) and massive (>10 M_sun) bipolar outflow ... More
Massive molecular outflowsDec 21 2001We present a mapping study of massive molecular outflows in 26 high-mass star-forming regions at 11'' spatial resolution. Bipolar morpholgy is found in 80% of the sources and the collimation is higher than previously thought. Additionally, we find that ... More
The distance to a star forming region in the Outer arm of the GalaxyJan 16 2009We performed astrometric observations with the VLBA of WB89-437, an H2O maser source in the Outer spiral arm of the Galaxy. We measure an annual parallax of 0.167 +/- 0.006 mas, corresponding to a heliocentric distance of 6.0 +/- 0.2 kpc or a Galactocentric ... More
Circumstellar ammonia in oxygen-rich evolved starsOct 03 2017The circumstellar ammonia (NH$_3$) chemistry in evolved stars is poorly understood. Previous observations and modelling showed that NH$_3$ abundance in oxygen-rich stars is several orders of magnitude above that predicted by equilibrium chemistry. In ... More
Distances to Galactic methanol masersDec 04 2008Dec 09 2008We present the first EVN parallax measurements of 6.7 GHz methanol masers in star forming regions of the Galaxy. The 6.7 GHz methanol maser transition is a very valuable astrometric tool, for its large stability and confined velocity spread, which makes ... More
Redshifted Neutral Hydrogen 21cm Absorption toward Red QuasarsSep 03 1997We have searched for redshifted neutral hydrogen 21cm absorption toward sources from the Stickel et al. `red quasar' sub-sample. Five of these red quasars have been searched for redshifted HI 21cm absorption to optical depth levels of a few percent, and ... More
Imaging the z=0.9 Absorbing Cloud toward 1830-211Jan 15 1998We present spectroscopic imaging observations of the molecular and HI 21cm absorbing cloud at z = 0.885 toward the `Einstein ring' radio source PKS 1830-211. We derive a cloud size between 10 h^{-1} pc and 600 h^{-1} pc, and M(H_2) > 2.6x10^{4} h^{-2} ... More
Distance of W3(OH) by VLBI annual parallax measurementSep 14 2004The most powerful tool for measuring distances within our Galaxy is the annual parallax. We carried out phase-referencing VLBI observations of H$_{2}$O masers in the star forming region W3(OH) with respect to the extragalactic continuum source ICRF 0244+624 ... More
Massive molecular outflowsOct 16 2001Well established correlations of low-mass flows show a continuity in the high-mass regime, and mean accretion rates for L>1000 Lsun are dM/dt~10^(-4) Msun/yr. We also present a tight correlation between outflow masses and core masses, which implies that ... More
Redshifted molecular absorption systems towards PKS1830-211 and B0218+357: submillimeter CO, CI and H2O dataAug 19 1997We have detected the J=4-3 rotational transition of 12CO in absorption at z=0.89 towards the quasar PKS1830-211, but not the 12CO 5-4 or the 3P1-3P0 fine structure line of neutral carbon. The intervening molecular medium thus has a total 12CO column density ... More
A Parallax-based Distance Estimator for Spiral Arm SourcesApr 08 2016The spiral arms of the Milky Way are being accurately located for the first time via trigonometric parallaxes of massive star forming regions with the BeSSeL Survey, using the Very Long Baseline Array and the European VLBI Network, and with the Japanese ... More
Radio continuum monitoring of the extreme carbon star IRC+10216Mar 21 2006We describe Very Large Array observations of the extreme carbon star IRC+10216 at 8.4, 14.9, and 22.5 GHz made over a two year period. We find possible variability correlated with the infrared phase and a cm- to sub-millimeter wavelength spectral index ... More
Submillimeter-wave emission of three Galactic red novae: cool molecular outflows produced by stellar mergersApr 04 2018May 23 2018Red novae are optical transients erupting at luminosities typically higher than those of classical novae. Their outbursts are believed to be caused by stellar mergers. We present millimeter/submillimeter-wave observations with ALMA and SMA of the three ... More
A high-sensitivity 6.7 GHz methanol maser survey toward H2O sourcesMar 16 2008We present the results of a high sensitivity survey for 6.7 GHz methanol masers towards 22 GHz water maser using the 100 m Efflesberg telescope. A total of 89 sources were observed and 10 new methanol masers were detected. The new detections are relatively ... More
High-Mass Proto-Stellar Candidates - II : Density structure from dust continuum and CS emissionOct 16 2001We present a detailed 1.2 mm continuum and CS spectral line study of a large sample of 69 massive star forming regions in very early stages of evolution, most of them prior to building up an ultracompact HII region. The continuum data show a zoo of different ... More
CH3OH and H2O masers in high-mass star-forming regionsMay 21 2002We present a comparison of ClassII CH3OH and H2O masers at high spatial resolution in a sample of 29 massive star-forming regions. Absolute positions of both maser types are compared with mm dust continuum, cm continuum and mid-infrared sources. Spatial ... More
Ammonia from cold high-mass clumps discovered in the inner Galactic disk by the ATLASGAL surveyAug 23 2012The APEX Telescope Large Area Survey: The Galaxy (ATLASGAL) is an unbiased continuum survey of the inner Galactic disk at 870 \mu m. It covers +/- 60 deg in Galactic longitude and aims to find all massive clumps at various stages of high-mass star formation ... More
The size, luminosity and motion of the extreme carbon star IRC+10216 (CW Leonis)May 30 2012Jun 30 2012Very Large Array observations of the extreme carbon star IRC+10216 at 7 mm wavelength with 40 milli-arcsecond resolution resolve the object's radio emission, which forms an almost round uniform disk of 83 milli arcseconds diameter, corresponding to 11 ... More
Initial phases of massive star formation in high infrared extinction clouds. II. Infall and onset of star formationOct 07 2012The onset of massive star formation is not well understood because of observational and theoretical difficulties. To find the dense and cold clumps where massive star formation can take place, we compiled a sample of high infrared extinction clouds, which ... More
High-Mass Proto-Stellar Candidates - I : The Sample and Initial ResultsOct 16 2001We describe a systematic program aimed at identifying and characterizing candidate high-mass proto-stellar objects (HMPOs). Our candidate sample consists of 69 objects selected by criteria based on those established by Ramesh & Sridharan (1997) using ... More
Diversity of chemistry and excitation conditions in the high-mass star forming complex W33Sep 25 2014The object W33 is a giant molecular cloud that contains star forming regions at various evolutionary stages from quiescent clumps to developed H II regions. Since its star forming regions are located at the same distance and the primary material of the ... More
Temperature structures in Galactic Center clouds - Direct evidence for gas heating via turbulenceJul 12 2016The Central Molecular Zone (CMZ) at the center of our Galaxy is the best template to study star formation processes under extreme conditions, similar to those in high-redshift galaxies. We observed on-the-fly maps of para-H$_{2}$CO transitions at 218 ... More
Initial phases of massive star formation in high infrared extinction clouds. I. Physical parametersMar 26 2010May 11 2010The earliest phases of massive star formation are found in cold and dense infrared dark clouds (IRDCs). Since the detection method of IRDCs is very sensitive to the local properties of the background emission, we present here an alternative method to ... More
An Interferometric Spectral-Line and Imaging Survey of VY Canis Majoris in the 345 GHz BandSep 27 2013A spectral line survey of the oxygen-rich red supergiant VY Canis Majoris was made between 279 and 355 GHz with the Submillimeter Array. Two hundred twenty three spectral features from 19 molecules (not counting isotopic species of some of them) were ... More
Proper Motions in the Andromeda SubgroupAug 13 2007This article presents results of VLBI observations of regions of H2O maser activity in the Local Group galaxies M33 and IC10. Since all position measurements were made relative to extragalactic background sources, the proper motions of the two galaxies ... More
86 GHz SiO maser survey of late-type stars in the Inner Galaxy II. Infrared photometry of the SiO Target StarsJan 14 2004We present a compilation and study of DENIS, 2MASS, ISOGAL, MSX and IRAS 1--25 micron photometry for a sample of 441 late-type stars in the inner Galaxy, which we previously searched for 86 GHz SiO maser emission (Messineo et al.2002). The comparison ... More
86 GHz SiO maser survey of late-type stars in the Inner Galaxy. I. Observational dataJul 12 2002We present 86 GHz (v = 1, J = 2 -1) SiO maser line observations with the IRAM 30-m telescope of a sample of 441 late-type stars in the Inner Galaxy (-4 degr < l < +30 degr). These stars were selected on basis of their infrared magnitudes and colours from ... More
Evidence of a pure starburst nature of the nuclear region of NGC 253Feb 06 2009We present high-resolution spectral line and continuum VLBI and VLA observations of the nuclear region of NGC 253 at 22 GHz. While the water vapor masers in this region were detected on arcsecond and milliarcsecond scales, we could not detect any compact ... More
II. Accurate Positions and Proper Motions of Stellar SiO Masers near the Galactic CenterDec 11 2002Menten, Reid, Eckart and Genzel (1997) accurately determined the position of Sgr A* on an infrared image, by aligning the infrared image with positions measured for SiO masers, associated with infrared-bright evolved stars, at radio wavelengths. We now ... More
Imaging the Ionized Disk of the High-Mass Protostar Orion-IApr 18 2007We have imaged the enigmatic radio source-I (Orion-I) in the Orion-KL nebula with the VLA at 43 GHz with 34 mas angular resolution. The continuum emission is highly elongated and is consistent with that expected from a nearly edge-on disk. The high brightness ... More
Outflow 20--2000 AU from a High-Mass Protostar in W51-IRS2Dec 04 2001We present the results of the first high angular resolution observations of SiO maser emission towards the star forming region W51-IRS2 made with the Very Large Array (VLA) and Very Long Baseline Array (VLBA). Our images of the water maser emission in ... More
Studying High Redshift Star Forming Galaxies at Centimeter and Millimeter WavelengthsJul 30 1999Aug 25 1999We discuss various aspects of centimeter and millimeter wavelength continuum and line observations of high redshift star forming galaxies. Perhaps the most important lesson is that sensitive observations at submm through cm wavelengths reveal a population ... More
Search for Cold Debris Disks around M-dwarfsSep 20 2006Debris disks are believed to be related to planetesimals left over around stars after planet formation has ceased. The frequency of debris disks around M-dwarfs which account for 70% of the stars in the Galaxy is unknown while constrains have already ... More
A Trigonometric Parallax of Sgr B2Aug 25 2009Aug 26 2009We have measured the positions of water masers in Sgr B2, a massive star forming region in the Galactic center, relative to an extragalactic radio source with the Very Long Baseline Array. The positions measured at 12 epochs over a time span of one year ... More
Trigonometric Parallaxes of Massive Star Forming Regions: III. G59.7+0.1 and W 51 IRS2Nov 05 2008We report trigonometric parallaxes for G59.7+0.1 and W 51 IRS2, corresponding to distances of 2.16^{+0.10}_{-0.09} kpc and 5.1^{+2.9}_{-1.4} kpc, respectively. The distance to G59.7+0.1 is smaller than its near kinematic distance and places it between ... More
Redshifted formaldehyde from the gravitational lens B0218+357Jun 22 2007Jun 25 2007The gravitational lens toward B0218+357 offers the unique possibility to study cool moderately dense gas with high sensitivity and angular resolution in a cloud that existed half a Hubble time ago. Observations of the radio continuum and six formaldehyde ... More
The Proper Motion of the Local Group Galaxy IC 10Oct 26 2006We have measured the proper motion of the Local Group galaxy IC 10 with the Very Long Baseline Array by measuring the position of an H2O maser relative to two background quasars over 4.3 years. After correction for the rotation of the Milky Way and IC ... More
A multi-transition submillimeter water maser study of evolved stars - detection of a new line near 475 GHzOct 27 2007Context: Maser emission from the H2O molecule probes the warm, inner circumstellar envelopes of oxygen-rich red giant and supergiant stars. Multi-maser transition studies can be used to put constraints on the density and temperature of the emission regions. ... More
Discovery of a bright radio transient in M82: a new radio supernova?Apr 15 2009May 28 2009In this Letter, we report the discovery of a new bright radio transient in M82. Using the Very Large Array, we observed the nuclear region of M82 at several epochs at 22 GHz and detected a new bright radio source in this galaxy's central region. We find ... More
86 GHz SiO maser survey of late-type stars in the Inner Galaxy. IV. SiO emission and infrared data for sources in the Scutum and Sagittarius-Carina arms, 20 deg < l < 50 degJun 06 2018We present an 86 GHz SiO (v = 1, J = 2 ---> 1) maser search toward late-type stars located within |b|<0.5 deg and 20 deg < l < 50 deg. This search is an extension at longer longitudes of a previously published work. We selected 135 stars from the MSX ... More
6.7 GHz methanol absorption toward the Seyfert 2 galaxy NGC 3079May 07 2008The detection of the 6.7 GHz line of methanol (CH3OH) is reported for the first time toward an object beyond the Magellanic Clouds. Using the Effelsberg 100 m telescope, two absorption features were identified toward the Seyfert 2 galaxy NGC 3079. Both ... More
Trigonometric Parallaxes of Massive Star Forming Regions: II. Cep A & NGC 7538Nov 05 2008We report trigonometric parallaxes for the sources NGC 7538 and Cep A, corresponding to distances of 2.65 [+0.12/-0.11] kpc and 0.70 [+0.04/-0.04] kpc, respectively. The distance to NGC 7538 is considerably smaller than its kinematic distance and places ... More
Structure and Dynamics of the Milky Way: an Astro2010 Science White PaperFeb 23 2009Mar 10 2009Recent advances in radio astrometry with the VLBA have resulted in near micro-arcsecond accurate trigonometric parallax and proper motion measurements for masers in star forming regions. We are now poised to directly measure the full 3-dimensional locations ... More
86 GHz SiO maser survey of late-type stars in the Inner Galaxy III. Interstellar extinction and colours of the SiO targetsMar 08 2005We have determined extinction corrections for a sample of 441 late-type stars in the inner Galaxy, which we previously searched for SiO maser emission, using the 2MASS near-infrared photometry of the surrounding stars. From this, the near-infrared extinction ... More
Motions of Galaxies in the Local Group and Beyond: an Astro2010 Science White PaperFeb 23 2009Mar 10 2009Recent advances with the VLBA have resulted in ~10 micro-arcsec astrometry for compact sources in external galaxies, and measurement of the proper motion of Local Group galaxies has been demonstrated. With improved telescopes and equipment, we could greatly ... More
The Distance and Size of the Red Hypergiant NML Cyg from VLBA and VLA AstrometryJul 08 2012We have measured the annual parallax and proper motion of NML Cyg from multiple epoch VLBA observations of the circulstellar H2O and SiO masers. The measured parallax of NML Cyg is 0.620+/-0.047 mas, corresponding to a distance of 1.61+/-0.12 kpc. The ... More
Trigonometric Parallaxes of Massive Star Forming Regions: V. G23.01-0.41 and G23.44-0.18Nov 05 2008We report trigonometric parallaxes for the massive star-forming regions G23.01-0.41 and G23.44-0.18, corresponding to distances of 4.59 [+0.38/-0.33] kpc and 5.88 [+1.37/-0.93] kpc, respectively. The distance to G23.01-0.41 is smaller than its near kinematic ... More
Search for Compact Extragalactic Radio Sources Near Massive Star Forming RegionsJun 16 2006We have used the Very Large Array to search for compact milliarcsecond-size radio sources near methanol masers in high-mass star-forming regions. Such sources are required for Very Long Baseline Interferometry phase-referencing observations. We conducted ... More
Trigonometric Parallaxes of Massive Star Forming Regions: I. S 252 & G232.6+1.0Nov 04 2008We are conducting a large program with the NRAO Very Long Baseline Array (VLBA) to measure trigonometric parallaxes of massive star-forming regions across the Milky Way. Here we report measurement of the parallax and proper motion of methanol masers in ... More
Synchrotron emission from the T Tauri binary system V773 Tau AApr 06 2006The pre-main sequence binary system V773 Tau A shows remarkable flaring activity around periastron passage. Here, we present the observation of such a flare at a wavelength of 3 mm (90 GHz) performed with the Plateau de Bure Interferometer. We examine ... More
Probing the obscuring medium around active nuclei using masers: The case of 3C403Aug 18 2004We report the first detection of a water megamaser in a radio-loud galaxy, 3C403, and present a follow-up study using the VLA. 3C403 has been observed as a part of a small sample of FRII galaxies with evidence of nuclear obscuration. The isotropic luminosity ... More
Towards a kinematic model of the Local GroupNov 07 2006Measuring the proper motions and geometric distances of galaxies within the Local Group is very important for our understanding of the history, present state and future of the Local Group. Currently, proper motion measurements using optical methods are ... More
The Position, Motion, and Mass of Sgr A*Apr 04 2003We report progress on measuring the position of Sgr A* on infrared images, placing limits on the motion of the central star cluster relative to Sgr A*, and measuring the proper motionof Sgr A* itself. The position of Sgr A* has been determined to within ... More
Exploring molecular complexity with ALMA (EMoCA): Detection of three new hot cores in Sagittarius B2(N)Mar 28 2017The SgrB2 molecular cloud contains several sites forming high-mass stars. SgrB2(N) is one of its main centers of activity. It hosts several compact and UCHII regions, as well as two known hot molecular cores (SgrB2(N1) and SgrB2(N2)), where complex organic ... More
The Distance to the Perseus Spiral Arm in the Milky WayDec 08 2005We have measured the distance to the massive star-forming region W3OH in the Perseus spiral arm of the Milky Way to be 1.95 $\pm$ 0.04 kilo-parsecs ($5.86\times10^{16}$ km). This distance was determined by triangulation, with the Earth's orbit as one ... More
The Position of Sagittarius A*: III. Motion of the Stellar CuspDec 07 2006Apr 03 2007In the first two papers of this series, we determined the position of Sgr A* on infrared images, by aligning the positions of red giant stars with positions measured at radio wavelengths for their circumstellar SiO masers. In this paper, we report detections ... More
Search for Cold Debris Disks around M-dwarfs. IIJul 27 2009Although 70 % of the stars in the Galaxy are M-dwarfs, thermal emission searches for cold debris disks have been conducted mostly for A-type and solar-type stars. We report on new lambda=1.2 mm continuum observations of thirty M-dwarfs, using the MAMBO-2 ... More
First redshift determination of an optically/UV faint submillimeter galaxy using CO emission linesSep 17 2009We report the redshift of a distant, highly obscured submm galaxy (SMG), based entirely on the detection of its CO line emission. We have used the newly commissioned Eight-MIxer Receiver (EMIR) at the IRAM 30m telescope, with its 8 GHz of instantaneous ... More
Distance and Kinematics of the Red Hypergiant VY CMa: VLBA and VLA AstrometrySep 14 2011We report astrometric results of phase-referencing VLBI observations of 43 GHz SiO maser emission toward the red hypergiant VY Canis Majoris (\vycma) using the Very Long Baseline Array (VLBA). We measured a trigonometric parallax of 0.83 $\pm$ 0.08 mas, ... More