- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/611/A66
- Title:
- AR Sco VLA radio observations
- Short Name:
- J/A+A/611/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AR Scorpii is unique amongst known white dwarf binaries in showing powerful pulsations extending to radio frequencies. Here we aim to investigate the multi-frequency radio emission of AR Sco in detail, in order to constrain its origin and emission mechanisms. We present interferometric radio frequency imaging of AR Sco at 1.5, 5 and 9GHz, analysing the total flux and polarization behaviour of this source at high time resolution (10, 3 and 3s), across a full 3.6h orbital period in each band. We find strong modulation of the radio flux on the orbital period and the orbital sideband of the white dwarf's spin period (also known as the "beat" period). This indicates that, like the optical flux, the radio flux arises predominantly from on or near the inner surface of the M-dwarf companion star. The beat-phase pulsations of AR Sco decrease in strength with decreasing frequency. They are strongest at 9GHz and at an orbital phase ~0.5. Unlike the optical emission from this source, radio emission from AR Sco shows weak linear polarization but very strong circular polarization, reaching ~30% at an orbital phase ~0.8. We infer the probable existence of a non-relativistic cyclotron emission component, which dominates at low radio frequencies. Given the required magnetic fields, this also likely arises from on or near the M-dwarf.
- ID:
- ivo://CDS.VizieR/J/A+A/487/383
- Title:
- Ar XVIII radiative and excitation rates
- Short Name:
- J/A+A/487/383
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we report on calculations for energy levels, radiative rates, collision strengths, and effective collision strengths for transitions among the lowest 25 levels of the n<=5 configurations of H-like Ar XVIII. The general-purpose relativistic atomic structure package (GRASP) and Dirac atomic R-matrix code (DARC) are adopted for the calculations. Radiative rates, oscillator strengths, and line strengths are reported for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among the 25 levels. Furthermore, collision strengths and effective collision strengths are listed for all 300 transitions among the above 25 levels over a wide energy (temperature) range up to 800Ryd (10^7.4^K).
1104. 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.
- ID:
- ivo://CDS.VizieR/J/AJ/161/203
- Title:
- A sample of 7146 M or K-dwarfs from KIC and Gaia
- Short Name:
- J/AJ/161/203
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The planet-metallicity correlation serves as a potential link between exoplanet systems as we observe them today and the effects of bulk composition on the planet formation process. Many observers have noted a tendency for Jovian planets to form around stars with higher metallicities; however, there is no consensus on a trend for smaller planets. Here, we investigate the planet-metallicity correlation for rocky planets in single and multi-planet systems around Kepler M-dwarf and late-K-dwarf stars. Due to molecular blanketing and the dim nature of these low-mass stars, it is difficult to make direct elemental abundance measurements via spectroscopy. We instead use a combination of accurate and uniformly measured parallaxes and photometry to obtain relative metallicities and validate this method with a subsample of spectroscopically determined metallicities. We use the Kolmogorov-Smirnov (K-S) test, Mann-Whitney U-test, and Anderson-Darling (AD) test to compare the compact multiple planetary systems with single-transiting planet systems and systems with no detected transiting planets. We find that the compact multiple planetary systems are derived from a statistically more metal-poor population, with a p-value of 0.015 in the K-S test, a p-value of 0.005 in the Mann-Whitney U-test, and a value of 2.574 in the AD test statistic, which exceeds the derived threshold for significance by a factor of 25. We conclude that metallicity plays a significant role in determining the architecture of rocky planet systems. Compact multiples either form more readily, or are more likely to survive on gigayear timescales, around metal-poor stars.
- ID:
- ivo://CDS.VizieR/J/A+A/613/A72
- Title:
- AS1063 and MACS1206-08 datacubes
- Short Name:
- J/A+A/613/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from the KMOS LENsing Survey (KLENS), which is exploiting gravitational lensing to study the kinematics of 24 star-forming galaxies at 1.4<z<3.5 with a median mass of log(M*/M_{sun}_)=9.6 and a median star formation rate (SFR) of 7.5M_{sun}/yr. We find that 25% of these low mass/low SFR galaxies are rotation-dominated, while the majority of our sample shows no velocity gradient. When combining our data with other surveys, we find that the fraction of rotation-dominated galaxies increases with the stellar mass, and decreases for galaxies with a positive offset from the main sequence (higher specific star formation rate). We also investigate the evolution of the intrinsic velocity dispersion, sigma_0_, as a function of the redshift, z, and stellar mass, M*, assuming galaxies in quasi-equilibrium (Toomre Q parameter equal to 1). From the z-sigma_0_ relation, we find that the redshift evolution of the velocity dispersion is mostly expected for massive galaxies (log(M*/M_{sun}_)>10). We derive a M*-sigma_0_ relation, using the Tully-Fisher relation, which highlights that a different evolution of the velocity dispersion is expected depending on the stellar mass, with lower velocity dispersions for lower masses, and an increase for higher masses, stronger at higher redshift. The observed velocity dispersions from this work and from comparison samples spanning 0<z<3.5 appear to follow this relation, except at higher redshift (z>2), where we observe higher velocity dispersions for low masses (log(M*/M_{sun}_)~9.6) and lower velocity dispersions for high masses (log(M*/M_{sun}_)~10.9) than expected. This discrepancy could, for instance, suggest that galaxies at high redshift do not satisfy the stability criterion, or that the adopted parametrization of the specific star formation rate and molecular properties fail at high redshift.
- ID:
- ivo://CDS.VizieR/J/PAZh/36/600
- Title:
- ASAS 101538-5933.1 BV light curves
- Short Name:
- J/PAZh/36/600
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the plate collection of the Harvard College Observatory, we have obtained 528 photographic magnitude estimates for the recently discovered long-period classical Cepheid ASAS 101538-5933.1 (P=51.4-days). Together with the published photoelectric and CCD observations, our data have allowed us to construct an O-C diagram spanning a time interval of 120 years. The O-C diagram has the shape of a parabola, which has made it possible to determine for the first time the quadratic light elements and to calculate the rate of evolutionary increase in the period, dP/dt=51.8(+/-4.8)s/yr or (dP/dt)/P=7.3(+/-0.7)s, in agreement with the results of theoretical calculations for the third crossing of the instability strip. The available data reduced by the method of Eddington and Plakidis reveal small random period fluctuations that do not distort the evolutionary trend in the O-C residuals.
- ID:
- ivo://CDS.VizieR/J/MNRAS/395/593
- Title:
- ASAS chromospherically active eclipsing binaries
- Short Name:
- J/MNRAS/395/593
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have started a spectroscopic survey to identify new chromospherically active components and low-mass pre-main sequence (PMS) stars in recently discovered All Sky Automated Survey (ASAS) eclipsing binaries. In this paper, we briefly describe our scientific motivation, the observing tools and the results obtained from the first phase of this survey. Using the available observing facilities in India, the spectroscopic observations of a sample of 180 candidate eclipsing binary stars selected from ASAS-I&II releases were carried out during 2004-2006. The strength of Halpha emission was used to characterize the level of chromospheric activity. Our spectroscopic survey reveals that out of 180 stars about 36 binary systems show excess Halpha emission. One of the objects in our sample, ASAS 081700-4243.8, displays very strong Halpha emission. Follow-up high-resolution spectroscopic observations reveal that this object is indeed very interesting and most likely a classical Be-type system with K0III companion.
- ID:
- ivo://CDS.VizieR/J/MNRAS/400/969
- Title:
- ASAS detached eclipsing binaries parameters
- Short Name:
- J/MNRAS/400/969
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive the absolute physical and orbital parameters for a sample of 18 detached eclipsing binaries from the All-Sky Automated Survey (ASAS) data base based on the available photometry and our own radial velocity (RV) measurements. The RVs are computed using spectra we collected with the 3.9-m Anglo-Australian Telescope (AAT) and its University College London Echelle Spectrograph (UCLES), and the 1.9-m Radcliffe telescope and its Grating Instrument for Radiation Analysis with a Fibre-Fed Echelle (GIRAFFE) at the South African Astronomical Observatory (SAAO). In order to obtain as precise RVs as possible, most of the systems were observed with an iodine cell available at the AAT/UCLES and/or analysed using the two-dimensional cross-correlation technique (TODCOR). The RVs were measured with TODCOR using synthetic template spectra as references.
