- ID:
- ivo://CDS.VizieR/J/MNRAS/496/2663
- Title:
- Canes Venatici I images with LOFAR
- Short Name:
- J/MNRAS/496/2663
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dwarf galaxies are dark matter-dominated and therefore promising targets for the search for weakly interacting massive particles (WIMPs), which are well-known candidates for dark matter. Annihilation of WIMPs produce ultra-relativistic cosmic-ray electrons and positrons that emit synchrotron radiation in the presence of magnetic fields. For typical magnetic field strengths (few G) and O(GeV-TeV) WIMP masses (and thus typical electron energies of the same order) this emission peaks at hundreds of MHz. Here, we use the non-detection of 150-MHz radio continuum emission from the dwarf spheroidal galaxy 'Canes Venatici I' with the LOw-Frequency ARray (LO-FAR) to derive constraints on the annihilation cross section of WIMPs into primary electron-positron and other fundamental particle-antiparticle pairs. In this first-of-its-kind LOFAR study, we obtain new constraints on annihilating WIMP dark matter (DM). Using conservative estimates for the magnetic field strengths and diffusion coefficients, we obtain limits that are comparable with those by the Fermi Large Area Telescope (Fermi-LAT) using gamma-ray observations. Assuming s-wave annihilation and WIMPs making up 100% of the DM density, our limits exclude several thermal WIMP realisations in the [2, 20]-GeV mass range. A more ambitious multi-wavelength and multi-target LOFAR study could improve these limits by a few orders of magnitude.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/612/A110
- Title:
- Cas A LOFAR and VLA images
- Short Name:
- J/A+A/612/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cassiopeia A is one of the best-studied supernova remnants. Its bright radio and X-ray emission is due to shocked ejecta. Cas A is rather unique in that the unshocked ejecta can also be studied: through emission in the infrared, the radio-active decay of ^44^Ti, and the low-frequency free-free absorption caused by cold ionised gas, which is the topic of this paper. Free-free absorption processes are acted by the mass, geometry, temperature, and ionisation conditions in the absorbing gas. Observations at the lowest radio frequencies can constrain a combination of these properties. We used Low Frequency Array (LOFAR) Low Band Antenna observations at 30-77MHz and Very Large Array (VLA) L-band observations at 1-2GHz to fit for internal absorption as parametrised by the emission measure. We simultaneously fit multiple UV-matched images with a common resolution of 17" (this corresponds to 0.25pc for a source at the distance of Cas A). The ample frequency coverage allows us separate the relative contributions from the absorbing gas, the unabsorbed front of the shell, and the absorbed back of the shell to the emission spectrum. We explored the effects that a temperature lower than the ~100-500K proposed from infrared observations and a high degree of clumping can have on the derived physical properties of the unshocked material, such as its mass and density. We also compiled integrated radio flux density measurements, fit for the absorption processes that occur in the radio band, and considered their ect on the secular decline of the source. We find a mass in the unshocked ejecta of M=2.95+/-0.48M_{sun}_ for an assumed gas temperature of T=100K. This estimate is reduced for colder gas temperatures and, most significantly, if the ejecta are clumped.We measure the reverse shock to have a radius of 114+/-6" and be centred at 23:23:26, +58:48:54 (J2000).We also find that a decrease in the amount of mass in the unshocked ejecta (as more and more material meets the reverse shock and heats up) cannot account for the observed low-frequency behaviour of the secular decline rate. To reconcile our low-frequency absorption measurements with models that reproduce much of the observed behaviour in Cas A and predict little mass in the unshocked ejecta, the ejecta need to be very clumped or the temperature in the cold gas needs to be low (~10K). Both of these options are plausible and can together contribute to the high absorption value that we find.
- ID:
- ivo://CDS.VizieR/VIII/94
- Title:
- Catalog of extended extragalactic radio sources
- Short Name:
- VIII/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalog of extended extragalactic radio sources consisting of 10460 objects is compiled based on the list of radio sources of the FIRST survey. A total of 2339 objects are identified with galaxies and quasars of the SDSS survey and the Veron-Veron catalog. The distribution of position angles of the axes of radio sources from the catalog is determined, and the probability that this distribution is equiprobable is shown to be less than 10^-7^. This result implies that at Z equal to or smaller than 0.5, the spatial orientation of the axes of radio sources is anisotropic at a statistically significant level.
- ID:
- ivo://CDS.VizieR/VIII/20
- Title:
- Catalog of 5 GHz Galactic Plane Sources
- Short Name:
- VIII/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is a catalog of 915 sources in the galactic plane between l=190 - 360 - 40 for -2 < b < 2. The l, b pair of galactic coordinates is given in columns 1 and 2 and essentially constitutes the galactic source name. The 1950 equatorial coordinates for each source are given in columns 3 and 4, and values for the peak brightness temperature and flux density are given in columns 5 and 6. The reader should refer to Section 3 of the source reference for information relating to the determination of the flux densities. Column 7 gives an estimate of the source extension in minutes of arc. Extents are given for source in nonconfused regions only. Finally, in column 8 comments on each source are included where appropriate. Identifications with known supernova remnants are included from the compilation of Clark and Caswell (1976MNRAS.174..267C). Identifications with HII regions are based principally on H109alpha recombination-line emission data, which are mostly obtained from Wilson et al. (1970A&A.....6..364W) but with some unpublished Parkes observations included also.
- ID:
- ivo://CDS.VizieR/J/ApJS/238/9
- Title:
- Catalog of giant radio sources known to date
- Short Name:
- J/ApJS/238/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 349 giant radio sources (GRSs including both galaxies and quasars). The database contains all giants known to date from the literature. These GRSs cover the redshift range of 0.016<z<3.22 and include radio sources of projected linear sizes larger than 0.7Mpc, which extend up to 4.7Mpc. We provide the principal parameters (i.e., exact position of the host in the sky, redshift, angular and projected linear size, red optical magnitude, radio morphology type, total radio flux density, and luminosity) for all the sources, as well as characteristics of the sample. Based on the distribution of GRSs in the sky, we identify regions where there is a paucity of giants, so that future surveys for this type of objects could concentrate primarily in these fields. From the analysis presented here, we estimate a lower limit for the expected number of GRSs as about 2000, for the resolution and sensitivity limits of FIRST, NRAO VLA Sky Survey and Sloan Digital Sky Survey surveys. Compared with earlier compilations, there is a significant increase in the number of large giants with sizes >2Mpc, as well as those at high redshifts with z>1. We discuss aspects of their evolution and suggest that these are consistent with evolutionary models.
- ID:
- ivo://CDS.VizieR/J/ApJS/171/419
- Title:
- Catalog of LMC HI clouds
- Short Name:
- J/ApJS/171/419
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 21cm neutral hydrogen interferometric survey of the Large Magellanic Cloud (LMC) combined with the Parkes multibeam HI single-dish survey (2003MNRAS.339...87S) clearly shows that the HI gas is distributed in the form of clumps or clouds. The HI clouds and clumps have been identified using a thresholding method with three separate brightness temperature thresholds (T_b_). Each catalog of HI cloud candidates shows a power-law relationship between the sizes and the velocity dispersions of the clouds roughly following the Larson law scaling {sigma}_v_{prop.to}R^0.5^, with steeper indices associated with dynamically hot regions. The clouds in each catalog have roughly constant virial parameters as a function of mass, suggesting that the clouds are all in roughly the same dynamical state, but the values of the virial parameter are significantly larger than unity, showing that turbulent motions dominate gravity in these clouds. The mass distribution of the clouds is a power law with differential indices between -1.6 and -2.0 for the three catalogs. In contrast, the distribution of mean surface densities is a lognormal distribution.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A167
- Title:
- Catalog of NLS1s galaxies in 6dFGS survey
- Short Name:
- J/A+A/615/A167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new accurate catalog of narrow-line Seyfert 1 galaxies (NLS1s) in the southern hemisphere from the Six-degree Field Galaxy Survey (6dFGS) final data release, which is currently the most extensive spectroscopic survey available in the southern sky whose database has not yet been systematically explored. We classified 167 sources as NLS1s based on their optical spectral properties. We derived flux-calibrated spectra for the first time that the 6dFGS does not provide. By analyzing these spectra, we obtained strong correlations between the monochromatic luminosity at 5100 Angstrom and the luminosities of H-beta and [OIII] lines. The central black hole mass and the Eddington ratio have average values of 0.86x10^7^M_{sun}_ and 0.96L_Edd_ respectively, which are typical values for NLS1s. In the sample, 23 (13.8%) NLS1s were detected at radio frequencies, and 12 (7.0%) of them are radio-loud. Our results confirmed that radio-loud sources tend to have higher redshift, a more massive black hole, and higher radio and optical luminosities than radio-quiet sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/382/412
- Title:
- Catalog of SDSS-DR5/2MASS spectroscopic quasars
- Short Name:
- J/MNRAS/382/412
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 13444 SDSS-DR5 spectroscopic quasars which have an 2MASS near-IR counterpart within 5" of their position.
- ID:
- ivo://CDS.VizieR/V/112A
- Title:
- Catalog of Star-Forming Regions in the Galaxy
- Short Name:
- V/112A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This Catalog of Star-Forming Regions in the Galaxy contains coordinates and fluxes of young objects in the radio and infrared, as well as data on the radial velocities of recombination and molecular lines, for more than three thousand star-forming regions. In addition to photometric and kinematic data, we present information on diffuse and reflecting nebulae, dark and molecular clouds, and other objects related to young stars. The catalog consists of two parts. The main catalog lists star-forming regions in order of Galactic longitude and is supplemented by analogous information for star-forming regions in complexes of dark clouds with large angular sizes that are closest to the Sun. In our preliminary study of the catalog data using a formal classification of the star-forming regions, we subdivided these objects into several classes and characterized them as being populated primarily by massive or low-mass stars at early or late stages of the star-formation process. We also distinguish between relatively nearby and distant complexes.
- ID:
- ivo://CDS.VizieR/J/ApJ/848/34
- Title:
- CATalog of Stellar Unified Properties
- Short Name:
- J/ApJ/848/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Almost every star in our Galaxy is likely to harbor a terrestrial planet, but accurate measurements of an exoplanet's mass and radius demand accurate knowledge of the properties of its host star. The imminent TESS and CHEOPS missions are slated to discover thousands of new exoplanets. Along with WFIRST, which will directly image nearby planets, these surveys make urgent the need to better characterize stars in the nearby solar neighborhood (<30pc). We have compiled the CATalog of Stellar Unified Properties (CATSUP) for 951 stars, including such data as: Gaia astrometry; multiplicity within stellar systems; stellar elemental abundance measurements; standardized spectral types; CaII H and K stellar activity indices; GALEX NUV and FUV photometry; and X-ray fluxes and luminosities from ROSAT, XMM, and Chandra. We use this data-rich catalog to find correlations, especially between stellar emission indices, colors, and galactic velocity. Additionally, we demonstrate that thick-disk stars in the sample are generally older, have lower activity, and have higher velocities normal to the galactic plane. We anticipate that CATSUP will be useful for discerning other trends among stars within the nearby solar neighborhood, for comparing thin-disk versus thick-disk stars, for comparing stars with and without planets, and for finding correlations between chemical and kinematic properties.
