- ID:
- ivo://CDS.VizieR/J/A+A/572/A63
- Title:
- Intensity maps in the star-forming complex W33
- Short Name:
- J/A+A/572/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The object W33 is a giant molecular cloud that contains star forming regions at various evolutionary stages from quiescent clumps to developed HII regions. Since its star forming regions are located at the same distance and the primary material of the birth clouds is probably similar, we conducted a comparative chemical study to trace the chemical footprint of the different phases of evolution. We observed six clumps in W33 with the Atacama Pathfinder Experiment (APEX) telescope at 280GHz and the Submillimeter Array (SMA) at 230GHz. We detected 27 transitions of 10 different molecules in the APEX data and 52 transitions of 16 different molecules in the SMA data. The chemistry on scales larger than ~0.2pc, which are traced by the APEX data, becomes more complex and diverse the more evolved the star forming region is. On smaller scales traced by the SMA data, the chemical complexity and diversity increase up to the hot core stage. In the HII region phase, the SMA spectra resemble the spectra of the protostellar phase. Either these more complex molecules are destroyed or their emission is not compact enough to be detected with the SMA. Synthetic spectra modelling of the H_2_CO transitions, as detected with the APEX telescope, shows that both a warm and a cold component are needed to obtain a good fit to the emission for all sources except for W33 Main1. The temperatures and column densities of the two components increase during the evolution of the star forming regions. The integrated intensity ratios N_2_H^+^(3-2)/CS(6-5) and N_2_H^+^(3-2)/H_2_CO(4_2,2_-3_2,1_) show clear trends as a function of evolutionary stage, luminosity, luminosity-to-mass ratio, and H_2_ peak column density of the clumps and might be usable as chemical clocks.
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Search Results
- ID:
- ivo://CDS.VizieR/VIII/60
- Title:
- Interferometer phase calibration sources
- Short Name:
- VIII/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalogue contains compact radio sources with accurate positions observed with the Very Large Array (VLA). These sources are primarily intended for use as phase calibration sources for the Multi-Element Radio Linked Interferometer Network (MERLIN); the sources are also suitable as phase calibrators for the VLA and can be considered as candidate phase calibrators for very long-baseline interferometry (VLBI) networks. The accuracy of the position is 12 mas for sources in Paper I, 14 mas for sources in Paper II, and 55 mas for sources in Paper III.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/159
- Title:
- Interferometric CO obs. of 126 CALIFA galaxies
- Short Name:
- J/ApJ/846/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present interferometric CO observations, made with the Combined Array for Millimeter-wave Astronomy (CARMA) interferometer, of galaxies from the Extragalactic Database for Galaxy Evolution survey (EDGE). These galaxies are selected from the Calar Alto Legacy Integral Field Area (CALIFA) sample, mapped with optical integral field spectroscopy. EDGE provides good-quality CO data (3{sigma} sensitivity {Sigma}_mol_~11M_{sun}/pc^2^ before inclination correction, resolution ~1.4kpc) for 126 galaxies, constituting the largest interferometric CO survey of galaxies in the nearby universe. We describe the survey and data characteristics and products, then present initial science results. We find that the exponential scale lengths of the molecular, stellar, and star-forming disks are approximately equal, and galaxies that are more compact in molecular gas than in stars tend to show signs of interaction. We characterize the molecular-to-stellar ratio as a function of Hubble type and stellar mass and present preliminary results on the resolved relations between the molecular gas, stars, and star-formation rate. We then discuss the dependence of the resolved molecular depletion time on stellar surface density, nebular extinction, and gas metallicity. EDGE provides a key data set to address outstanding topics regarding gas and its role in star formation and galaxy evolution, which will be publicly available on completion of the quality assessment.
- ID:
- ivo://CDS.VizieR/J/ApJ/654/527
- Title:
- Interferometric observations of northern Be stars
- Short Name:
- J/ApJ/654/527
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first K'-band, long-baseline interferometric observations of the northern Be stars {gamma} Cas, {phi} Per, {zeta} Tau, and {kappa} Dra. The measurements were made with multiple telescope pairs of the CHARA Array interferometer and in every case the observations indicate that the circumstellar disks of the targets are resolved. We fit the interferometric visibilities with predictions from a simple disk model that assumes an isothermal gas in Keplerian rotation. We derive fits of the four model parameters (disk base density, radial density exponent, disk normal inclination, and position angle) for each of the targets.
- ID:
- ivo://CDS.VizieR/J/ApJ/873/91
- Title:
- Interferometric obs. of B-type stars with CHARA
- Short Name:
- J/ApJ/873/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present interferometric observations of 25 spectral type-B stars that were made with the Precision Astronomical Visible Observations and the CLassic Interferometry with Multiple Baselines beam combiners at the Center for High Angular Resolution Astronomy Array (CHARA). The observations provide the angular sizes of these stars with an average error of 6%. The stars range in size from 1.09mas for {beta} Tau down to 0.20mas for 32 Ori. We collected ultraviolet to infrared spectrophotometry and derived temperatures, angular diameters, and reddening estimates that best fit the spectra, as well as solutions with the angular size fixed by the interferometric measurements. There is generally good agreement between the observed and spectral fit angular diameters, indicating that the fluxes predicted from model atmospheres are reliable. On the other hand, the temperatures derived from angular diameters and fluxes tend to be larger (by ~4%) than those from published results based on analysis of the line spectrum. This discrepancy may in part be attributed to unexplored atmospheric parameters or the existence of unknown companions. The physical radii of the stars are calculated from the angular diameters and Gaia DR2 parallaxes, and the target stars are placed in the Hertzsprung-Russell diagram for comparison with evolutionary tracks.
- ID:
- ivo://CDS.VizieR/J/AJ/152/213
- Title:
- Interferometry and spectroscopy of sigma Orionis
- Short Name:
- J/AJ/152/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present interferometric observations of the {sigma} Orionis triple system using the CHARA Array, NPOI, and VLTI. Using these measurements, we spatially resolve the orbit of the close spectroscopic binary (Aa,Ab) for the first time and present a revised orbit for the wide pair (A,B). Combining the visual orbits with previously published radial velocity measurements and new radial velocities measured at CTIO, we derive dynamical masses for the three massive stars in the system of M_Aa_=16.99+/-0.20M_{Sun}_, M_Ab_=12.81+/-0.18M_{Sun}_, and M_B_=11.5+/-1.2M_{Sun}_. The inner and outer orbits in the triple are not coplanar, with a relative inclination of 120{deg}-127{deg}. The orbital parallax provides a precise distance of 387.5+/-1.3pc to the system. This is a significant improvement over previous estimates of the distance to the young {sigma} Orionis cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/545/A130
- Title:
- Interferometry of {alpha} Eri
- Short Name:
- J/A+A/545/A130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectrally resolved long-baseline optical/IR interferometry of rotating stars opens perspectives to investigate their fundamental parameters and the physical mechanisms that govern their interior, photosphere, and circumstellar envelope structures. Aims. Based on the signatures of stellar rotation on observed interferometric wavelength-differential phases, we aim to measure angular diameters, rotation velocities, and orientation of stellar rotation axes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/443/1629
- Title:
- Interferometry of chemically peculiar stars
- Short Name:
- J/MNRAS/443/1629
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By means of numerical experiments we explore the application of interferometry to the detection and characterization of abundance spots in chemically peculiar (CP) stars using the brightest star {epsilon} UMa as a case study. We find that the best spectral regions to search for spots and stellar rotation signatures are in the visual domain. The spots can clearly be detected already at a first visibility lobe and their signatures can be uniquely disentangled from that of rotation. The spots and rotation signatures can also be detected in near-infrared at low spectral resolution but baselines longer than 180m are needed for all potential CP candidates. According to our simulations, an instrument like VEGA (or its successor e.g. Fibered and spectrally Resolved Interferometric Equipment New Design) should be able to detect, in the visual, the effect of spots and spots+rotation, provided that the instrument is able to measure V_2_~10^-3^, and/or closure phase. In infrared, an instrument like AMBER but with longer baselines than the ones available so far would be able to measure rotation and spots. Our study provides necessary details about strategies of spot detections and the requirements for modern and planned interferometric facilities essential for CP star research.
- ID:
- ivo://CDS.VizieR/J/MNRAS/474/4937
- Title:
- Interplanetary scintillation at 162 and 1400MHz
- Short Name:
- J/MNRAS/474/4937
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first astrophysical application of the technique of wide-field interplanetary scintillation (IPS) with the Murchison Widefield Array (MWA). This powerful technique allows us to identify and measure sub-arcsecond compact components in low-frequency radio sources across large areas of sky without the need for long-baseline interferometry or ionospheric calibration. We present the results of a 5-min observation of a 30x30deg^2^ MWA field at 162MHz with 0.5s time resolution. Of the 2550 continuum sources detected in this field, 302 (12 per cent) show rapid fluctuations caused by IPS. We find that at least 32 per cent of bright low-frequency radio sources contain a sub-arcsecond compact component that contributes over 40 per cent of the total flux density. Perhaps surprisingly, peaked-spectrum radio sources are the dominant population among the strongly scintillating, low-frequency sources in our sample. While gamma-ray active galactic nuclei are generally compact, flat-spectrum radio sources at higher frequencies (162MHz), the properties of many of the Fermi blazars in our field are consistent with a compact component embedded within more extended low-frequency emission. The detection of a known pulsar in our field shows that the wide-field IPS technique is at the threshold of sensitivity needed to detect new pulsars using image plane analysis, and scaling the current MWA sensitivity to that expected for SKA-low implies that large IPS-based pulsar searches will be feasible with SKA. Calibration strategies for the SKA require a better knowledge of the space density of compact sources at low radio frequencies, which IPS observations can now provide.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/2965
- Title:
- Interplanetary scintillation at 79 and 158MHz
- Short Name:
- J/MNRAS/473/2965
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first dedicated observations of Interplanetary Scintillation (IPS) with the Murchison Widefield Array. We have developed a synthesis imaging technique, tailored to the properties of modern 'large-N' low-frequency radio telescopes. This allows us to image the variability on IPS time-scales across 900deg^2^ simultaneously. We show that for our observations, a sampling rate of just 2Hz is sufficient to resolve the IPS signature of most sources. We develop tests to ensure that IPS variability is separated from ionospheric or instrumental variability. We validate our results by comparison with existing catalogues of IPS sources, and near-contemporaneous observations by other IPS facilities. Using just 5 min of data, we produce catalogues at both 79 and 158MHz, each containing over 350 scintillating sources. At the field centre, we detect approximately one scintillating source per square degree, with a minimum scintillating flux density at 158MHz of 110mJy, corresponding to a compact flux density of approximately 400mJy. Each of these sources is a known radio source, however only a minority were previously known to contain sub-arcsecond components. We discuss our findings and the prospects they hold for future astrophysical and heliospheric studies.
