- ID:
- ivo://CDS.VizieR/J/PAZh/42/200
- Title:
- Dispersion measure of Milky Way and MC pulsars
- Short Name:
- J/PAZh/42/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A number of recent studies indicates a significant amount of ionized gas in a form of the hot gas halo around the Milky Way. The halo extends over the region of 100 kpc and may be acountable for the missing baryon mass. In this paper we calculate the contribution of the proposed halo to the dispersion measure (DM) of the pulsars. The Navarro, Frenk, and White (NFW), Maller and Bullock (MB), and Feldmann, Hooper, and Gnedin (FHG) density distributions are considered for the gas halo. The data set includes pulsars with the distance known independently from the DM, e.g., pulsars in globular clusters, LMC, SMC and pulsars with known parallax. The results exclude the NFW distribution for the hot gas, while the more realisticMB and FHG models are compatible with the observed dispersion measure.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/726/108
- Title:
- Dispersion-supported stellar systems
- Short Name:
- J/ApJ/726/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine scaling relations of dispersion-supported galaxies over more than eight orders of magnitude in luminosity by transforming standard fundamental plane parameters into a space of mass, radius, and luminosity. The radius variable r_1/2_ is the deprojected (three-dimensional) half-light radius, the mass variable M_1/2_ is the total gravitating mass within this radius, and L_1/2_ is half the luminosity. We find that from ultra-faint dwarf spheroidals to giant cluster spheroids, dispersion-supported galaxies scatter about a one-dimensional "fundamental curve" through this MRL space.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/133
- Title:
- Displaced red and blue components objects
- Short Name:
- J/MNRAS/457/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a feasibility study to determine the effectiveness of using USNO-B1.0 data to preferentially detect objects with displaced red and blue components. A procedure was developed to search catalogue entries for such objects, which include M dwarfs paired with white dwarfs or with earlier main-sequence stars, and galaxies with asymmetric colour distributions. Residual differences between red and blue and infrared and blue scanned emulsion images define vectors, which, when appropriately aligned and of sufficient length, signal potential candidates. Test sample sets were analysed to evaluate the effective discrimination of the technique. Over 91000 USNO-B1.0 catalogue entries at points throughout the celestial sphere were then filtered for acceptable combinations of entry observations and magnitudes and the resulting total of about 17000 entries was winnowed down to a little more than 200 objects of interest. These were screened by visual examination of photo images to a final total of 146 candidates. About one quarter of these candidates coincide with SDSS (Sloan Digital Sky Survey) data. Those constituents fall into two groups, single and paired objects. SDSS identified several galaxies in the first group. Regarding the second group, at least half of its members were tentatively identified as main-sequence pairs, the greater portion being of widely separated spectral types. Two white dwarf-main-sequence pairs were also identified. Most importantly, the vectors formed from USNO-B1.0 residuals were in alignment with corresponding SDSS pair position angles, thereby supporting this work's central thesis.
- ID:
- ivo://CDS.VizieR/J/ApJ/717/L6
- Title:
- Displacement of black hole in M87
- Short Name:
- J/ApJ/717/L6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Isophotal analysis of M87, using data from the Advanced Camera for Surveys, reveals a projected displacement of 6.8+/-0.8pc (~0.1") between the nuclear point source (presumed to be the location of the supermassive black hole, SMBH) and the photo-center of the galaxy. The displacement is along a position angle of 307+/-17{deg} and is consistent with the jet axis. This suggests the active SMBH in M87 does not currently reside at the galaxy center of mass, but is displaced in the counter-jet direction. Possible explanations for the displacement include orbital motion of an SMBH binary, gravitational perturbations due to massive objects (e.g., globular clusters), acceleration by an asymmetric or intrinsically one-sided jet, and gravitational recoil resulting from the coalescence of an SMBH binary.
- ID:
- ivo://CDS.VizieR/J/AJ/155/165
- Title:
- Dissipation in exoplanet hosts from tidal spin-up
- Short Name:
- J/AJ/155/165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stars with hot Jupiters (HJs) tend to rotate faster than other stars of the same age and mass. This trend has been attributed to tidal interactions between the star and planet. A constraint on the dissipation parameter Q_*_' follows from the assumption that tides have managed to spin up the star to the observed rate within the age of the system. This technique was applied previously to HATS-18 and WASP-19. Here, we analyze the sample of all 188 known HJs with an orbital period <3.5 days and a "cool" host star (T_eff_<6100 K). We find evidence that the tidal dissipation parameter (Q_*_') increases sharply with forcing frequency, from 10^5^ at 0.5 day^-1^ to 10^7^ at 2 day^-1^. This helps to resolve a number of apparent discrepancies between studies of tidal dissipation in binary stars, HJs, and warm Jupiters. It may also allow for a HJ to damp the obliquity of its host star prior to being destroyed by tidal decay.
- ID:
- ivo://CDS.VizieR/J/A+A/469/173
- Title:
- Dissipative structures of diffuse molecular gas
- Short Name:
- J/A+A/469/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- These maps are part of a large project aimed at analyzing the small scale morphology and velocity structure of the parsec-scale environment of a low mass dense core. The Polaris field is translucent and shows no signpost of star formation, therefore allowing an analysis of a purely turbulent field prior to star formation. Our work is based on large maps made with the IRAM-30m telescope in the two lowest rotational transitions of ^12^CO and ^13^CO (1-0) with high angular (20" or 0.015pc at 115GHz) and spectral (0.055km/s) resolutions. The new data superseeds the first IRAM Key-project of Falgarone et al. (1998A&A...331..669F, Cat. <VIII/66>). The field is centered at 02:00:06.0-87:42:04.1 (J2000); at the estimated distance of 150pc, the size of the maps are 0.72*0.55pc^2^.
- ID:
- ivo://CDS.VizieR/J/ApJ/706/727
- Title:
- Distance and mass of Infrared Dark Clouds
- Short Name:
- J/ApJ/706/727
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Infrared Dark Clouds (IRDCs) are dark clouds seen in silhouette in mid-infrared surveys. They are thought to be the birthplace of massive stars, yet remarkably little information exists on the properties of the population as a whole (e.g., mass spectrum, spatial distribution). Genetic forward modeling is used along with the Two Micron All Sky Survey and the Besancon Galactic model to deduce the three-dimensional distribution of interstellar extinction toward previously identified IRDC candidates. This derived dust distribution can then be used to determine the distance and mass of IRDCs, independently of kinematic models of the Milky Way. Along a line of sight that crosses an IRDC, the extinction is seen to rise sharply at the distance of the cloud. Assuming a dust-to-gas ratio, the total mass of the cloud can be estimated. The method has been successfully applied to 1259 IRDCs, including over 1000 for which no distance or mass estimate currently exists. The IRDCs are seen to lie preferentially along the spiral arms and in the molecular ring of the Milky Way, reinforcing the idea that they are the birthplace of massive stars. Also, their mass spectrum is seen to follow a power law with an index of -1.75+/-0.06, steeper than giant molecular clouds (GMCs) in the inner Galaxy but comparable to clumps in GMCs. This slope suggests that the IRDCs detected using the present method are not gravitationally bound, but are rather the result of density fluctuations induced by turbulence.
- ID:
- ivo://CDS.VizieR/J/A+A/522/A54
- Title:
- Distance determination for RAVE stars. II.
- Short Name:
- J/A+A/522/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The RAdial Velocity Experiment (RAVE) is a spectroscopic survey of the Milky Way which already collected over 400000 spectra of ~330000 different stars. We use the subsample of spectra with spectroscopically determined values of stellar parameters to determine the distances to these stars. The list currently contains 235064 high quality spectra which show no peculiarities and belong to 210872 different stars. The numbers will grow as the RAVE survey progresses. The distances are determined with a method based on the work by Breddels et al. (2010, Cat. J/A+A/511/A90). Here we assume that the star undergoes a standard stellar evolution and that its spectrum shows no peculiarities. The refinements include: the use of either of the three isochrone sets, a better account of the stellar ages and masses, use of more realistic errors of stellar parameter values, and application to a larger dataset. The derived distances of both dwarfs and giants match within ~21% to the astrometric distances of Hipparcos stars and to the distances of observed members of open and globular clusters. Multiple observations of a fraction of RAVE stars show that repeatability of the derived distances is even better, with half of the objects showing a distance scatter of <=11%. RAVE dwarfs are ~300pc from the Sun, and giants are at distances of 1 to 2kpc, and up to 10kpc. This places the RAVE dataset between the more local Geneva-Copenhagen survey and the more distant and fainter SDSS sample. As such it is ideal to address some of the fundamental questions of Galactic structure and evolution in the pre-Gaia era. Individual applications are left to separate papers, here we show that the full 6-dimensional information on position and velocity is accurate enough to discuss the vertical structure and kinematic properties of the thin and thick disks.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/637
- Title:
- Distance-limited sample of MYSOs
- Short Name:
- J/MNRAS/452/637
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse C^18^O (J=3-2) data from a sample of 99 infrared (IR)-bright massive young stellar objects (MYSOs) and compact HII regions that were identified as potential molecular-outflow sources in the Red MSX Source survey. We extract a distance-limited (D<6kpc) sample shown to be representative of star formation covering the transition between the source types. At the spatial resolution probed, Larson-like relationships are found for these cores, though the alternative explanation, that Larson's relations arise where surface-density-limited samples are considered, is also consistent with our data. There are no significant differences found between source properties for the MYSOs and HII regions, suggesting that the core properties are established prior to the formation of massive stars, which subsequently have little impact at the later evolutionary stages investigated. There is a strong correlation between dust-continuum and C^18^O-gas masses, supporting the interpretation that both trace the same material in these IR-bright sources. A clear linear relationship is seen between the independently established core masses and luminosities. The position of MYSOs and compact HII regions in the mass-luminosity plane is consistent with the luminosity expected from the most massive protostar in the cluster when using an ~40 percent star formation efficiency and indicates that they are at a similar evolutionary stage, near the end of the accretion phase.
- ID:
- ivo://CDS.VizieR/J/A+AS/113/325
- Title:
- Distance measurements of Lynds Nebulae
- Short Name:
- J/A+AS/113/325
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A literature search has been carried out in order to obtain a distance table for the Lynds galactic nebulae which in the main have been cited in Astronomy and Astrophysics Abstracts between 1980 and 1984. Inevitably this list cannot be without omission and a request is made for any further information which could lead to the publication of a more complete compilation.