- ID:
- ivo://CDS.VizieR/J/AJ/131/633
- Title:
- A ROSAT survey of contact binary stars
- Short Name:
- J/AJ/131/633
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Contact binary stars are common variable stars that are all believed to emit relatively large fluxes of X-rays. In this work we combine a large new sample of contact binary stars derived from the ROTSE-I telescope (Cat. <J/AJ/131/621>) with X-ray data from the ROSAT All Sky Survey (RASS, Cat. <IX/10>) to estimate the X-ray volume emissivity of contact binary stars in the Galaxy. We obtained X-ray fluxes for 140 contact binaries from the RASS, as well as two additional stars observed by the XMM-Newton observatory.
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- ID:
- ivo://CDS.VizieR/J/ApJ/799/10
- Title:
- Arp 220 6 and 33GHz images
- Short Name:
- J/ApJ/799/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new Karl G. Jansky Very Large Array radio continuum images of the nuclei of Arp 220, the nearest ultra-luminous infrared galaxy. These new images have both the angular resolution to study the detailed morphologies of the two nuclei that power the galaxy merger and sensitivity to a wide range of spatial scales. At 33GHz, we achieve a resolution of 0.081"x0.063" (29.9x23.3pc) and resolve the radio emission surrounding both nuclei. We conclude from the decomposition of the radio spectral energy distribution that a majority of the 33GHz emission is synchrotron radiation. The spatial distributions of radio emission in both nuclei are well described by exponential profiles. These have deconvolved half-light radii (R_50d_) of 51 and 35pc for the eastern and western nuclei, respectively, and they match the number density profile of radio supernovae observed with very long baseline interferometry. This similarity might be due to the fast cooling of cosmic rays electrons caused by the presence of a strong (~mG) magnetic field in this system. We estimate extremely high molecular gas surface densities of 2.2_-1.0_^+2.1^x10^5^M_{sun}_/pc^2^ (east) and 4.5_-1.9_^+4.5^x10^5^M_{sun}_/pc^2^ (west), corresponding to total hydrogen column densities of N_H_=2.7_-1.2_^+2.7^x10^25^cm^-2^ (east) and 5.6_-2.4_^+5.5^x10^25^cm^-2^ (west). The implied gas volume densities are similarly high, n_H2_~3.8_-1.6_^+3.8^x10^4^cm^-3^ (east) and ~11_-4.5_^+12^x10^4^cm^-3^ (west). We also estimate very high luminosity surface densities of {Sigma}_IR_~4.2_-0.7_^+1.6^x10^13^L_{sun}_/kpc^2^ (east) and {Sigma}_IR_ ~ 9.7_-2.4_^+3.7^x10^13^_L_{sun}/kpc^2^ (west), and star formation rate surface densities of {Sigma}_SFR_~10^3.7+/-0.1^M_{sun}_/yr/kpc^2^ (east) and {Sigma}_SFR_~10^4.1+/-0.1^M_{sun}_/yr/kpc^2^ (west). These values, especially for the western nucleus are, to our knowledge, the highest luminosity surface densities and star formation rate surface densities measured for any star-forming system. Despite these high values, the nuclei appear to lie below the dusty Eddington limit in which radiation pressure is balanced only by self-gravity. The small measured sizes also imply that at wavelengths shorter than {lambda}=1mm, dust absorption effects must play an important role in the observed light distribution while below 5GHz free-free absorption contributes substantial opacity. According to these calculations, the nuclei of Arp 220 are only transparent in the frequency range ~5-350GHz. Our results offer no clear evidence that an active galactic nucleus dominates the emission from either nucleus at 33GHz.
- ID:
- ivo://CDS.VizieR/J/AJ/136/614
- Title:
- Arp 2 and Ter 8 red giants equivalent widths
- Short Name:
- J/AJ/136/614
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To compare the globular clusters (GCs) associated with the Sagittarius Galaxy (Sgr) we report the results obtained from new high-resolution spectra of red giant stars in Terzan 8 and Arp 2, collected with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph at Las Campanas Observatory.
- ID:
- ivo://CDS.VizieR/J/A+A/621/A25
- Title:
- Arp 240 Fabry-Perot interferometry
- Short Name:
- J/A+A/621/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Encounters between galaxies modify their morphology, kinematics, and star formation history. The relation between these changes and external perturbations is not straightforward. The great number of parameters involved requires both the study of large samples and individual encounters where particular features, motions, and perturbations can be traced and analysed in detail. We analysed the morphology, kinematics, and dynamics of two luminous infrared spiral galaxies of almost equal mass, NGC 5257 and NGC 5258, in which star formation is mostly confined to the spiral arms, in order to understand interactions between galaxies of equivalent masses and star-forming processes during the encounter. Using scanning Fabry-Perot interferometry, we studied the contribution of circular and non-circular motions and the response of the ionized gas to external perturbations. We compared the kinematics with direct images of the pair and traced the star-forming processes and gravitational effects due to the presence of the other galaxy. The spectral energy distribution of each member of the pair was fitted. A mass model was fitted to the rotation curve of each galaxy. Large, non-circular motions detected in both galaxies are associated with a bar, spiral arms, and HII regions for the inner parts of the galaxies, and with the tidal interaction for the outer parts of the discs. Bifurcations in the rotation curves indicate that the galaxies have recently undergone their pericentric passage. The pattern speed of a perturbation of one of the galaxies is computed. Location of a possible corotation seems to indicate that the gravitational response of the ionized gas in the outer parts of the disc is related to the regions where ongoing star formation is confined. The spectral energy distribution (SED) fit indicates a slightly different star formation history for each member of the pair. For both galaxies, a pseudo-isothermal halo better fits the global mass distribution.
- ID:
- ivo://CDS.VizieR/J/A+A/590/A25
- Title:
- Arp 220 HCN and HCO^+^ data cubes
- Short Name:
- J/A+A/590/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin of the enormous luminosities of the two opaque nuclei of Arp 220, the prototypical ultra-luminous infrared galaxy, remains a mystery because we lack observational tools to explore the innermost regions around the nuclei. We explore the potential of imaging vibrationally excited molecular emission at high angular resolution to better understand the morphology and physical structure of the dense gas in Arp 220 and to gain insight into the nature of the nuclear powering sources. The Atacama Large Millimeter/submillimeter Array (ALMA) provided simultaneous observations of HCN, HCO^+^, and vibrationally excited HCN v_2_=1f emission. Their J=4-3 and 3-2 transitions were observed at a matching resolution of ~0.5", which allows us to isolate the emission from the two nuclei.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A86
- Title:
- Arp 220 LOFAR radio images at 150MHz
- Short Name:
- J/A+A/593/A86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse new observations with the International Low Frequency Array (LOFAR) telescope, and archival data from the Multi-Element Radio Linked Interferometer Network (MERLIN) and the Karl G. Jansky Very Large Array (VLA). We model the spatially resolved radio spectrum of Arp 220 from 150MHz to 33GHz. We present an image of Arp 220 at 150MHz with resolution 0.65"x0.35", sensitivity 0.15mJy/beam, and integrated flux density 394+/-59mJy. More than 80% of the detected flux comes from extended (6"~2.2kpc) steep spectrum (alpha=-0.7) emission, likely from star formation in the molecular disk surrounding the two nuclei. We find elongated features extending 0.3" (110pc) and 0.9" (330pc) from the eastern and western nucleus respectively, which we interpret as evidence for outflows. The extent of radio emission requires acceleration of cosmic rays far outside the nuclei. We find that a simple three component model can explain most of the observed radio spectrum of the galaxy. When accounting for absorption at 1.4GHz, Arp 220 follows the FIR/radio correlation with q=2.36, and we estimate a star formation rate of 220M_{sun}_/yr. We derive thermal fractions at 1GHz of less than 1% for the nuclei, which indicates that a major part of the UV-photons are absorbed by dust. International LOFAR observations shows great promise to detect steep spectrum outflows and probe regions of thermal absorption. However, in LIRGs the emission detected at 150MHz does not necessarily come from the main regions of star formation. This implies that high spatial resolution is crucial for accurate estimates of star formation rates for such galaxies at 150MHz.
- ID:
- ivo://CDS.VizieR/VII/192
- Title:
- Arp's Peculiar Galaxies
- Short Name:
- VII/192
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Halton C. Arp photographed 338 views of notable peculiar galaxies and published them as his 1966 "Atlas of Peculiar Galaxies." Since then, galaxy catalogs have named 585 of the involved galaxies. This contemporary index collects names and characteristics of the involved objects for use by contemporary observers of the historical views.
- ID:
- ivo://CDS.VizieR/J/A+A/562/A121
- Title:
- ARRAKIS: Atlas of Resonance Rings as Known In S4G
- Short Name:
- J/A+A/562/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Resonance rings and pseudorings (here collectively called "rings") are thought to be related to the gathering of material near dynamical resonances caused by non-axisymmetries in galaxy discs. Therefore, they are the consequence of secular evolution processes that redistribute material and angular momentum in discs. Their study may give clues on the formation and growth of bars and other disc non-axisymmetries. Our aims are to produce a Catalogue and an Atlas of the rings detected in the Spitzer Survey of Stellar Structure in Galaxies (S4G) and to conduct a statistical study of the data in the Catalogue. We traced the contours of rings previously identified by Buta et al. (in preparation) and fitted them with ellipses. We found the orientation of bars by studying the galaxy ellipse fits from S4G's Pipeline4. We used the galaxy orientation data obtained by S4G's Pipeline 4 to obtain intrinsic ellipticities and orientations of rings and the bars. ARRAKIS contains data on 724 ringed galaxies in the S4G. The frequency of resonance rings in the S4G is of 16+/-1% and 35+/-1% for outer and inner features, respectively. Outer rings are mostly found in Hubble stages -1<=T<=4. Inner rings are found in a broad distribution that covers the range -1<=T<=7. We confirm that outer rings have two preferred orientations, namely parallel and perpendicular to the bar. We confirm a tendency for inner rings to be oriented parallel to the bar, but we report the existence of a significant fraction (maybe as large as 50%) of inner features that have random orientations with respect to the bar. These misaligned inner rings are mostly found in late-type galaxies (T>=4). We find that the fraction of barred galaxies hosting outer (inner) rings is ~1.7 times (~1.3 times) that in unbarred galaxies. We confirm several results from previous surveys, as well as predictions from simulations of resonant rings and/or from manifold flux tube theory. We report that a significant fraction of inner rings in late-type galaxies have a random orientation with respect to the bar. This may be due to spiral modes decoupled from the bar dominating the Fourier amplitude spectrum at the radius of the inner ring. The fact that rings are only mildly favoured by bars suggests that those in unbarred galaxies either formed due to weak departures from the axisymmetry of the galactic potential or that they are born because of bars that have been destroyed after the ring formation.
899. AS 209 ALMA image
- ID:
- ivo://CDS.VizieR/J/A+A/610/A24
- Title:
- AS 209 ALMA image
- Short Name:
- J/A+A/610/A24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents new high angular resolution ALMA 1.3mm dust continuum observations of the protoplanetary system AS 209 in the Ophiuchus star forming region. The dust continuum emission is characterized by a main central core and two prominent rings at r=75au and r=130au intervaled by two gaps at at r=62au and r=103au. The two gaps have different widths and depths, with the inner one being narrower and shallower. We determined the surface density of the millimeter dust grains using the 3D radiative transfer disk code dali. According to our fiducial model the inner gap is partially filled with millimeter grains while the outer gap is largely devoid of dust. The inferred surface density is compared to 3D hydrodynamical simulations (FARGO-3D) of planet-disk interaction. The outer dust gap is consistent with the presence of a giant planet (M_planet_~0.8M_Saturn_); the planet is responsible for the gap opening and for the pile-up of dust at the outer edge of the planet orbit. The simulations also show that the same planet could be the origin of the inner gap at r=62au. The relative position of the two dust gaps is close to the 2:1 resonance and we have investigated the possibility of a second planet inside the inner gap. The resulting surface density (including location, width and depth of the two dust gaps) are in agreement with the observations. The properties of the inner gap pose a strong constraint to the mass of the inner planet (M_planet_<0.1M_J_). In both scenarios (single or pair of planets), the hydrodynamical simulations suggest a very low disk viscosity ({alpha}<10^-4^). Given the young age of the system (0.5-1Myr), this result implies that the formation of giant planets occurs on a timescale of <~1Myr.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/535
- Title:
- A sample of candidate radio stars
- Short Name:
- J/ApJ/701/535
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conduct a search for radio stars by combining radio and optical data from the FIRST survey (Cat. VIII/71) and the Sloan Digital Sky Survey (SDSS-DR6, Cat. II/282, obsoleted by II/294). The faint limit of SDSS makes possible a homogeneous search for radio emission from stars of low optical luminosity. We select a sample of 112 candidate radio stars in the magnitude range 15<i<~19.1 and with radio flux S_20_>=1.25mJy, from about 7000deg^2^ of sky. The selection criteria are positional coincidence within 1", radio and optical point source morphology, and an SDSS spectrum classified as stellar. The sample contamination is estimated by random matching to be 108+/-13, suggesting that at most a small fraction of the selected candidates are genuine radio stars. Therefore, we rule out a very rare population of extremely radio-loud stars: no more than 1.2 of every million stars in the magnitude range 15<i<19.1 stars has radio flux S_20_>=1.25mJy. We investigate the optical and radio colors of the sample to find candidates that show the largest likelihood of being real radio stars. The significant outliers from the stellar locus, as well as the magnetically active stars, are the best candidates for follow-up radio observations.
