Results for "Karl M. Menten"

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Atlas of Cosmic ray-induced astrochemistryNov 07 2018Nov 13 2018Cosmic-rays are the primary initiators of interstellar chemistry, and getting a better understanding of the varying impact they have on the chemistry of interstellar clouds throughout the Milky Way will not only expand our understanding of interstellar ... More
The Effect of Far-infrared Radiation on the Hyperfine Anomaly of the OH 18 cm TransitionJan 29 2019We present observations of the four hyperfine structure components of the OH 18 cm transition (1612, 1665, 1667 and 1720 MHz) toward Heiles Cloud 2 (HCL2) in Taurus and the dense cores L183 and L169. Toward the peculiar straight structure in the northern ... More
Mapping Spiral Structure on the far side of the Milky WayOct 17 2017Little is known about the portion of the Milky Way lying beyond the Galactic center at distances of more than 9 kilo-parsec from the Sun. These regions are opaque at optical wavelengths due to absorption by interstellar dust, and distances are very large ... More
Astro2020: Unlocking the Secrets of Late-Stage Stellar Evolution and Mass Loss through Radio Wavelength ImagingMar 13 2019During the late phases of evolution, low-to-intermediate mass stars like our Sun undergo periods of extensive mass loss, returning up to 80% of their initial mass to the interstellar medium. This mass loss profoundly affects the stellar evolutionary history, ... More
Submillimeter Array Observations of Magnetic Fields in G240.31+0.07: an Hourglass in a Massive Cluster-forming CoreSep 19 2014We report the first detection of an hourglass magnetic field aligned with a well-defined outflow-rotation system in a high-mass star-forming region. The observations were performed with Submillimeter Array toward G240.31+0.07, which harbors a massive, ... More
Non-circular Motions in the Outer Perseus Spiral ArmMar 26 2019We report measurements of parallax and proper motion for five 6.7-GHz methanol maser sources in the outer regions of the Perseus arm as part of the BeSSeL Survey of the Galaxy. By combining our results with previous astrometric results, we determine an ... More
The Parallax of the Red Hypergiant VX Sgr with Accurate Tropospheric Delay CalibrationApr 03 2018We report astrometric results of VLBI phase-referencing observations of 22 GHz \hho\ masers emission toward the red hypergiant \vxsgr, one of most massive and luminous red hypergiant stars in our Galaxy, using the Very Long Baseline Array. A background ... More
Observations of the Goldreich-Kylafis effect in star-forming regions with XPOL at the IRAM 30m telescopeOct 16 2008The Goldreich-Kylafis (GK) effect causes certain molecular line emission to be weakly linearly polarized, e.g., in the presence of a magnetic field. Compared to polarized dust emission, the GK effect has the potential to yield additional information along ... More
Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)Aug 23 2013The discovery of amino acids in meteorites and the detection of glycine in samples returned from a comet to Earth suggest that the interstellar chemistry is capable of producing such complex organic molecules. Our goal is to investigate the degree of ... More
Hot HCN around young massive stars at 0.1" resolutionMar 10 2011Mar 24 2011Massive stars form deeply embedded in dense molecular gas, which they stir and heat up and ionize. During an early phase, the ionization is confined to hypercompact HII regions, and the stellar radiation is entirely absorbed by dust, giving rise to a ... More
Unveiling a Compact Cluster of Massive and Young Stars in IRAS 17233-3606Jul 10 2008We have analyzed sensitive high spatial resolution archival radio continuum data at 1.3, 2.0, 3.6 and 6.0 cm as well as the H2O maser molecular line data obtained using the Very Large Array (VLA) in its hybrid AB configuration toward the high-mass star-forming ... More
Molecular Cloud-scale Star Formation in NGC 300May 09 2014We present the results of a galaxy-wide study of molecular gas and star formation in a sample of 76 HII regions in the nearby spiral galaxy NGC 300. We have measured the molecular gas at 250 pc scales using pointed CO(J=2-1) observations with the APEX ... More
A deep wide-field sub-mm survey of the Carina Nebula complexNov 12 2010The Great Nebula in Carina is a superb location in which to study the physics of violent massive star-formation and the resulting feedback effects, including cloud dispersal and triggered star-formation. In order to reveal the cold dusty clouds in the ... More
Detections of massive stars in the cluster MCM2005b77, in the star-forming regions GRS G331.34$-$00.36 (S62) and GRS G337.92$-$00.48 (S36)Jun 20 2018Large infrared and millimeter wavelength surveys of the Galactic plane have unveiled more than 600 new bubble HII regions and more than 3000 candidate star clusters. We present a study of the candidate clusters MCM2005b72, DBS2003-157, DBS2003-172, and ... More
Detection of a branched alkyl molecule in the interstellar medium: iso-propyl cyanideOct 09 2014The largest non-cyclic molecules detected in the interstellar medium (ISM) are organic with a straight-chain carbon backbone. We report an interstellar detection of a branched alkyl molecule, iso-propyl cyanide (i-C3H7CN), with an abundance 0.4 times ... More
Molecular Line Emission as a Tool for Galaxy Observations (LEGO). I. HCN as a tracer of moderate gas densities in molecular clouds and galaxiesJul 17 2017Trends observed in galaxies, such as the Gao \& Solomon relation, suggest a linear relation between the star formation rate and the mass of dense gas available for star formation. Validation of such relations requires the establishment of reliable methods ... More
From Poloidal to Toroidal: Detection of Well-ordered Magnetic Field in High-mass Proto-cluster G35.2-0.74NNov 04 2013We report on detection of an ordered magnetic field (B field) threading a massive star-forming clump in the molecular cloud G35.2-0.74, using Submillimeter Array observations of polarized dust emission. Thanks to the sensitive and high-angular-resolution ... More
The Galactic Center Molecular Cloud Survey. II. A Lack of Dense Gas & Cloud Evolution along Galactic Center OrbitsOct 11 2016Jun 08 2017We present the first systematic study of the density structure of clouds found in a complete sample covering all major molecular clouds in the Central Molecular Zone (CMZ; inner $\sim{}200~\rm{}pc$) of the Milky Way. This is made possible by using data ... More
Quasars in the MAMBO blank field surveyNov 04 2005Our MAMBO 1.2 mm blank field imaging survey of ~0.75 sqd has uncovered four unusually bright sources, with flux densities between 10 and 90 mJy, all located in the Abell 2125 field. The three brightest are flat spectrum radio sources with bright optical ... More
Dense Molecular Gas Excitation at High Redshift: Detection of HCO+(J=4-3) Emission in the Cloverleaf QuasarNov 03 2010We report the detection of HCO+(J=4-3) emission in the Cloverleaf Quasar at z=2.56, using the IRAM Plateau de Bure Interferometer. HCO+ emission is a star formation indicator similar to HCN, tracing dense molecular hydrogen gas (n(H2) ~= 10^5 cm^-3) within ... More
Robust Constraint on a Drifting Proton-to-Electron Mass Ratio at z=0.89 from Methanol Observation at Three Radio TelescopesNov 14 2013Dec 10 2013A limit on a possible cosmological variation of the proton-to-electron mass ratio $\mu$ is derived from methanol (CH$_3$OH) absorption lines in the benchmark PKS1830$-$211 lensing galaxy at redshift $z = 0.89$ observed with the Effelsberg 100-m radio ... More
The Proper Motions of the Double Radio Source n in the Orion BN/KL RegionDec 01 2016We have extended the time baseline for observations of the proper motions of radio sources in the Orion BN/KL region from 14.7 to 22.5 years. We present improved determinations for the sources BN and I. In addition, we address the proper motions of the ... More
On the Relationship of UC H II Regions and Class II Methanol Masers: I. Source CatalogsSep 12 2016We conducted VLA C-configuration observations to measure positions and luminosities of Galactic Class II 6.7 GHz methanol masers and their associated ultra-compact H II regions. The spectral resolution was 3.90625 kHz and the continuum sensitivity reached ... More
Modelling the abundance structure of isocyanic acid (HNCO) toward the low-mass solar type protostar IRAS 16293-2422Nov 02 2018Isocyanic acid (HNCO), the most stable of the simplest molecules containing the four main elements essential for organic chemistry, has been observed in several astrophysical environments such as molecular clouds, star-forming regions, external galaxies ... More
The Galactic Center Molecular Cloud Survey. I. A Steep Linewidth-Size Relation & Suppression of Star FormationOct 11 2016Nov 04 2016The Central Molecular Zone (CMZ; inner $\sim{}200~\rm{}pc$) of the Milky Way is a star formation (SF) environment with very extreme physical properties. Exploration of SF in this region is important because (i) this region allows us to test models of ... More
Submillimeter Polarimetry with PolKa, a reflection-type modulator for the APEX telescopeAug 21 2014Aug 29 2014Imaging polarimetry is an important tool for the study of cosmic magnetic fields. In our Galaxy, polarization levels of a few up to $\sim$10\% are measured in the submillimeter dust emission from molecular clouds and in the synchrotron emission from supernova ... More
Fire in the Heart: A Characterization of the High Kinetic Temperatures and Heating Sources in the Nucleus of NGC253Dec 21 2018Jan 18 2019The nuclear starburst within the central $\sim 15^{\prime\prime}$ ($\sim 250$ pc; $1^{\prime\prime} \simeq 17$ pc) of NGC253 has been extensively studied as a prototype for the starburst phase in galactic evolution. Atacama Large Millimeter/submillimeter ... More
First astrophysical detection of the helium hydride ion (HeH$^+$)Apr 21 2019During the dawn of chemistry when the temperature of the young Universe had fallen below $\sim$4000 K, the ions of the light elements produced in Big Bang nucleosynthesis recombined in reverse order of their ionization potential. With its higher ionization ... More
CO multi-line observations of HH 80-81: a two-component molecular outflow associated with the largest protostellar jet in our GalaxyDec 09 2018Stretching a length reaching 10 pc projected in the plane of sky, the radio jet associated with Herbig-Haro objects 80 and 81 (HH 80-81) is known as the largest and best collimated protostellar jet in our Galaxy. The nature of the molecular outflow associated ... More
The Clump Mass Function of the Dense Clouds in the Carina Nebula ComplexDec 18 2012We want to characterize the properties of the cold dust clumps in the Carina Nebula Complex (CNC), which shows a very high level of massive star feedback. We derive the Clump Mass Function (ClMF), explore the reliability of different clump extraction ... More
An Extensive, Sensitive Search for SiO Masers in High- and Intermediate-Mass Star-Forming RegionsAug 23 2008We present sensitive Very Large Array observations with an angular resolution of a few arcseconds of the $J= 1 - 0$ line of SiO in the $v$=1 and 2 vibrationally excited states toward a sample of 60 Galactic regions in which stars of high or intermediate ... More
Parallaxes for star forming regions in the inner Perseus spiral armMar 27 2019We report trigonometric parallax and proper motion measurements of 6.7-GHz CH3OH and 22-GHz H2O masers in eight high-mass star-forming regions (HMSFRs) based on VLBA observations as part of the BeSSeL Survey. The distances of these HMSFRs combined with ... More
The Population of Compact Radio Sources in the Orion Nebula ClusterMar 17 2016We present a deep centimeter-wavelength catalog of the Orion Nebula Cluster (ONC), based on a 30h single-pointing observation with the Karl G. Jansky Very Large Array in its high-resolution A-configuration using two 1 GHz bands centered at 4.7 GHz and ... More
Unveiling the chemistry of interstellar CH: Spectroscopy of the 2 THz $N=2\leftarrow 1$ ground state lineApr 12 2018The methylidyne radical CH is commonly used as a proxy for H$_2$ in the cold, neutral phase of the interstellar medium. The optical spectroscopy of CH is limited by interstellar extinction, whereas far-infrared observations provide an integral view through ... More
Near-infrared spectra of Galactic stellar clusters detected on Spitzer/GLIMPSE imagesMar 12 2009We present near-infrared spectroscopic observations of massive stars in three stellar clusters located in the direction of the inner Galaxy. One of them, the Quartet, is a new discovery while the other two were previously reported as candidate clusters ... More
Detection of interstellar ortho-D2H+ with SOFIAApr 08 2017We report on the detection of the ground-state rotational line of ortho-D2H+ at 1.477 THz (203 micron) using the German REceiver for Astronomy at Terahertz frequencies (GREAT) onboard the Stratospheric Observatory For Infrared Astronomy (SOFIA). The line ... More
SOFIA/GREAT Discovery of Terahertz Water MasersMay 26 2017We report the discovery of water maser emission at frequencies above 1 THz. Using the GREAT instrument on SOFIA, we have detected emission in the 1.296411 THz 8(27)-7(34) transition of water toward three oxygen-rich evolved stars: W Hya, U Her, and VY ... More
Astronomical detection of a radioactive molecule 26AlF in a remnant of an ancient explosionJul 27 2018Decades ago, $\gamma$-ray observatories identified diffuse Galactic emission at 1.809 MeV originating from $\beta^+$ decays of an isotope of aluminium, $^{26}$Al, that has a mean-life time of 1.04 Myr. Objects responsible for the production of this radioactive ... More
ATLASGAL-selected high-mass clumps in the inner Galaxy. VII. Characterisation of mid-J CO emissionDec 19 2018Jan 06 2019High-mass stars are formed within massive molecular clumps, where a large number of stars form close together. The evolution of the clumps with different masses and luminosities is mainly regulated by its high-mass stellar content and the formation of ... More
Molecular Gas in Redshift 6 Quasar Host GalaxiesFeb 08 2010We report our new observations of redshifted carbon monoxide emission from six z~6 quasars, using the PdBI. CO (6-5) or (5-4) line emission was detected in all six sources. Together with two other previous CO detections, these observations provide unique ... More
Molecular Gas in the Host Galaxy of a Quasar at Redshift z=6.42Jul 23 2003Observations of the molecular gas phase in quasar host galaxies provide fundamental constraints on galaxy evolution at the highest redshifts. Molecular gas is the material out of which stars form; it can be traced by spectral line emission of carbon--monoxide ... More
Star Formation in Quasar Host Galaxies at Redshift 6: Millimeter Surveys and New Insights from ALMASep 30 2012Nov 12 2012We have been carrying out a systematic survey of the star formation and ISM properties in the host galaxies of z~6 quasars. Our 250 GHz observations, together with available data from the literature, yield a sample of 14 z~6 quasars that are bright in ... 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.
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
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
ALMA and VLA measurements of frequency-dependent time lags in Sagittarius A*: evidence for a relativistic outflowFeb 11 2015Feb 12 2015Radio and mm-wavelength observations of Sagittarius A* (Sgr A*), the radio source associated with the supermassive black hole at the center of our Galaxy, show that it behaves as a partially self-absorbed synchrotron-emitting source. The measured size ... More
Rotational and high-resolution infrared spectrum of HC$_3$N: global ro-vibrational analysis and improved line catalogue for astrophysical observationsNov 23 2017HC$_3$N is an ubiquitous molecule in interstellar environments, from external galaxies, to Galactic interstellar clouds, star forming regions, and planetary atmospheres. Observations of its rotational and vibrational transitions provide important information ... More
High-resolution absorption spectroscopy of the OH 2Pi 3/2 ground state lineMar 08 2012Apr 12 2012The chemical composition of the interstellar medium is determined by gas phase chemistry, assisted by grain surface reactions, and by shock chemistry. The aim of this study is to measure the abundance of the hydroxyl radical (OH) in diffuse spiral arm ... More
Dimethyl ether in its ground state, v=0, and lowest two torsionally excited states, v11=1 and v15=1, in the high-mass star-forming region G327.3-0.6Feb 25 2013The goal of this paper is to determine the respective importance of solid state vs. gas phase reactions for the formation of dimethyl ether. This is done by a detailed analysis of the excitation properties of the ground state and the torsionally excited ... More
An ATCA Survey of Sagittarius~B2 at 7~mm: Chemical Complexity Meets Broadband InterferometryAug 10 2015We present a 30 - 50 GHz survey of Sagittarius B2(N) conducted with the Australia Telescope Compact Array (ATCA) with 5 - 10 arcsec resolution. This work releases the survey data and demonstrates the utility of scripts that perform automated spectral ... More
An Interferometric Spectral-line Survey of IRC+10216 in the 345 GHz BandDec 27 2010We report a spectral-line survey of the extreme carbon star IRC+10216 carried out between 293.9 and 354.8 GHz with the Submillimeter Array. A total of 442 lines were detected, more than 200 for the first time; 149 are unassigned. Maps at an angular resolution ... More
Gas dynamics of a luminous $z$ = 6.13 quasar ULAS J1319$+$0950 revealed by ALMA high resolution observationsJul 10 2017Jul 12 2017We present new Atacama Large Millimeter/submillimeter Array (ALMA) observations of the dust continuum and [C II] 158 $\mu$m fine structure line emission towards a far-infrared-luminous quasar, ULAS J131911.29$+$095051.4 at $z=6.13$, and combine the new ... More
The Bar and Spiral Structure Legacy (BeSSeL) Survey: Mapping the Milky Way with VLBI AstrometryFeb 25 2011Astrometric Very Long Baseline Interferometry (VLBI) observations of maser sources in the Milky Way are used to map the spiral structure of our Galaxy and to determine fundamental parameters such as the rotation velocity ($\Theta_0$) and curve and the ... More
Star Formation and Gas Kinematics of Quasar Host Galaxies at z~6: New insights from ALMAFeb 18 2013Jul 08 2013We present ALMA observations of the [C II] 158 micron fine structure line and dust continuum emission from the host galaxies of five redshift 6 quasars. We also report complementary observations of 250 GHz dust continuum and CO (6-5) line emission from ... More
Star Formation and ISM Properties in Host Galaxies of Three Far-infrared Luminous Quasars at $z\sim6$Mar 04 2019We present Karl G. Jansky Very Large Array (VLA) observations of the CO (2$-$1) line emission towards three far-infrared luminous quasars at $z\sim6$: SDSS J231038.88$+$185519.7 and SDSS J012958.51$-$003539.7 with $\sim0\farcs6$ resolution and SDSS J205406.42$-$000514.8 ... More
Submillimeter narrow emission lines from the inner envelope of IRC+10216Nov 13 2008A spectral-line survey of IRC+10216 in the 345 GHz band has been undertaken with the Submillimeter Array. Although not yet completed, it has already yielded a fairly large sample of narrow molecular emission lines with line-widths indicating expansion ... More
Submillimeter spectroscopy and astronomical searches of vinyl mercaptan, C$_2$H$_3$SHFeb 15 2019We have extended the pure rotational investigation of the two isomers syn and anti vinyl mercaptan to the millimeter domain using a frequency-multiplication spectrometer. The species were produced by a radiofrequency discharge in 1,2-ethanedithiol. Additional ... More
The LABOCA/ACT Survey of Clusters at All Redshifts: multi-wavelength analysis of background submillimeter galaxiesMar 03 2018Mar 06 2018We present a multi-wavelength analysis of 48 submillimeter galaxies (SMGs) detected in the LABOCA/ACT Survey of Clusters at All Redshifts, LASCAR, which acquired new 870 $\mu$m and ATCA 2.1 GHz observations of ten galaxy clusters detected through their ... More
Radio Measurements of the stellar proper motions in the core of the Orion Nebula ClusterNov 11 2016Using multi-epoch VLA observations, covering a time baseline of 29.1 years, we have measured the proper motions of 88 young stars with compact radio emission in the core of the Orion Nebula Cluster (ONC) and the neighboring BN/KL region. Our work increases ... More
On the nature of the compact sources in IRAS 16293-2422 seen in at centimeter to sub-millimeter wavelengthsMar 06 2019We present multi-epoch continuum observations of the Class 0 protostellar system IRAS 16293-2422 taken with the Very Large Array (VLA) at multiple wavelengths between 7 mm and 15 cm (41 GHz down to 2 GHz), as well as single-epoch Atacama Large Millimeter/submillimeter ... More
A Reverse Shock in GRB 160509AJun 28 2016We present the second multi-frequency radio detection of a reverse shock in a $\gamma$-ray burst. By combining our extensive radio observations of the Fermi-LAT GRB 160509A at $z = 1.17$ up to $20$ days after the burst with Swift X-ray observations and ... More
Molecular Bullets in A High-mass ProtostarApr 02 2019We present Submillimeter Array (SMA) observations in the CO J=3-2, SiO J=5-4 and 8-7, and SO 9_8-8_7 lines, as well as Atacama Pathfinder EXperiment (APEX) observations in the CO J=6-5 line, of an extremely high-velocity and jet-like outflow in high-mass ... More
An Isothermal Outflow in High-mass Star-forming Region G240.31+0.07May 10 2018We present Atacama Pathfinder EXperiment (APEX) observations toward the massive star-forming region G240.31+0.07 in the CO J = 3--2, 6--5, and 7--6 lines. We detect a parsec-sized, bipolar, and high velocity outflow in all the lines, which allow us, in ... More
G-virial: Gravity-based structure analysis of molecular cloudsApr 04 2015We present the G-virial method (available at which aims to quantify (1) the importance of gravity in molecular clouds in the position-position-velocity (PPV) space, and (2) properties of the gas condensations in molecular ... 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
A hot compact dust disk around a massive young stellar objectJul 28 2010Circumstellar disks are an essential ingredient of the formation of low-mass stars. It is unclear, however, whether the accretion-disk paradigm can also account for the formation of stars more massive than about 10 solar masses, in which strong radiation ... More
First results from VLTI near-infrared interferometry on high-mass young stellar objectsJul 30 2010Due to the recent dramatic technological advances, infrared interferometry can now be applied to new classes of objects, resulting in exciting new science prospects, for instance, in the area of high-mass star formation. Although extensively studied at ... More
The local spiral structure of the Milky WayOct 02 2016Oct 04 2016The nature of the spiral structure of the Milky Way has long been debated. Only in the last decade have astronomers been able to accurately measure distances to a substantial number of high-mass star-forming regions, the classic tracers of spiral structure ... More
An ALMA Survey of Submillimeter Galaxies in the Extended Chandra Deep Field South: Near-infrared morphologies and stellar sizesDec 01 2014We analyse HST WFC3/$H_{160}$-band observations of a sample of 48 ALMA-detected submillimeter galaxies (SMGs) in the Extended Chandra Deep Field South field, to study their stellar morphologies and sizes. We detect 79$\pm$17% of the SMGs in the $H_{160}$-band ... 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
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
The 2nd Generation z(Redshift) and Early Universe Spectrometer Part I: First-light observation of a highly lensed local-ULIRG analog at high-zNov 06 2013Nov 08 2013We report first science results from our new spectrometer, the 2nd generation z(Redshift) and Early Universe Spectrometer (ZEUS-2), recently commissioned on the Atacama Pathfinder Experiment telescope (APEX). ZEUS-2 is a submillimeter grating spectrometer ... More
High-mass star-forming cloud G0.38+0.04 in the Galactic Center Dust Ridge contains H2CO and SiO masersOct 21 2015Nov 16 2015We have discovered a new H$_2$CO (formaldehyde) $1_{1,0}-1_{1,1}$ 4.82966 GHz maser in Galactic Center Cloud C, G0.38+0.04. At the time of acceptance, this is the eighth region containing an H$_2$CO maser detected in the Galaxy. Cloud C is one of only ... More
Dense gas in the Galactic central molecular zone is warm and heated by turbulenceSep 04 2015The Galactic center is the closest region in which we can study star formation under extreme physical conditions like those in high-redshift galaxies. We measure the temperature of the dense gas in the central molecular zone (CMZ) and examine what drives ... More
Imaging the Radio Photospheres of Mira VariablesAug 16 2007We have used the VLA at 43 GHz to image the radio continuum emission from o Ceti, R Leo, and W Hya and to precisely locate their SiO maser emission with respect to the star. The radio continuum emission region for all three stars has a diameter close ... More
Preliminary Analysis of SOHO/STEREO Observations of Sungrazing Comet ISON (C/2012 S1) Around PerihelionJan 27 2014We present photometric and morphological analysis of the behavior of sungrazing comet C/2012 S1 ISON in SOHO and STEREO images around its perihelion on 2013 November 28.779 UT. ISON brightened gradually November 20-26 with a superimposed outburst on November ... More
Radio and X-ray variability of Young Stellar Objects in the Coronet ClusterSep 15 2005The Coronet Cluster in the nearby R CrA dark cloud offers the rare opportunity to study at least four "class I" protostellar sources as well as one candidate "class 0" source, a Herbig Ae star, and a candidate brown dwarf within a few square arcminutes ... More
Outflows, Accretion, and Clustered Protostellar Cores around a Forming O StarNov 27 2010We present a Submillimeter Array study in the 1.3 mm waveband of the NGC 7538 IRS 1--3 massive star-forming region. The brightest core in the mm continuum map, MM1, harbors the IRS 1 young O star. The core has a gas temperature of about 245 K and shows ... More
Herschel observations of interstellar chloroniumJan 13 2012Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared (HIFI), we have observed para-chloronium (H2Cl+) toward six sources in the Galaxy. We detected interstellar chloronium absorption in foreground molecular clouds along the ... More
The VLA view of the HL Tau Disk - Disk Mass, Grain Evolution, and Early Planet FormationMar 11 2016Mar 18 2016The first long-baseline ALMA campaign resolved the disk around the young star HL Tau into a number of axisymmetric bright and dark rings. Despite the very young age of HL Tau these structures have been interpreted as signatures for the presence of (proto)planets. ... More
First ALMA Light Curve Constrains Refreshed Reverse Shocks and Jet Magnetization in GRB 161219BAug 28 2018We present detailed multi-wavelength observations of GRB 161219B at $z=0.1475$, spanning the radio to X-ray regimes, and the first ALMA light curve of a GRB afterglow. The cm- and mm-band observations before $8.5$ d require emission in excess of that ... More
Detection of molecular gas in a distant submillimetre galaxy at z=4.76 with ATCAApr 22 2010Aug 10 2010We have detected the CO(2-1) transition from the submillimetre galaxy (SMG) LESSJ033229.4-275619 at z=4.755 using the new Compact Array Broadband Backend system on the Australian Telescope Compact Array. These data have identified a massive gas reservoir ... More
SOHO Comets: 20-Years and 3,000 Objects LaterNov 07 2016We present a summary of the more than 3,000 sungrazing and near-Sun comets discovered in coronagraph images returned by the Solar and Heliospheric Observatory (SOHO), since its launch in December 1995. We address each of the four main populations of objects ... More
BL Lac Contribution to the Extragalactic Gamma-Ray BackgroundMay 25 2007Nov 29 2007Very high energy gamma-rays from blazars traversing cosmological distances through the metagalactic radiation field can convert into electron-positron pairs in photon-photon collisions. The converted gamma-rays initiate electromagnetic cascades driven ... 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
Imaging the cold molecular gas in SDSS J1148 + 5251 at z = 6.4May 28 2015We present Karl G. Jansky Very Large Array (VLA) observations of the CO ($J = 2 \rightarrow 1$) line emission towards the $z = 6.419$ quasar SDSS J$114816.64+525150.3$ (J$1148+5251$). The molecular gas is found to be marginally resolved with a major axis ... 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
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
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
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
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
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
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
A submillimetre galaxy at z=4.76 in the LABOCA survey of the Extended Chandra Deep Field SouthFeb 25 2009We report on the identification of the highest redshift submm-selected source currently known: LESSJ033229.4-275619. This source was detected in the Large Apex BOlometer CAmera (LABOCA) Extended Chandra Deep Field South (ECDFS) Submillimetre Survey (LESS), ... 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