- 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/641/A22
- Title:
- CARLA J1103+3449 cluster datacube
- Short Name:
- J/A+A/641/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Passive early-type galaxies dominate cluster cores at z<~1.5. At higher redshift, cluster core galaxies are observed to have on-going star-formation, which is fuelled by cold molecular gas.We measured the molecular gas reservoir of the central region around the radioloud active galactic nucleus (AGN) in the cluster CARLA J1103+3449 at z=1.44 using NOEMA. The AGN synchrotron emission dominates the continuum emission at 94.48GHz, and we measured its flux at the AGN position and at the position of two radio jets. Combining our measurements with published results over the range 4.71GHz-94.5GHz, and assuming S_synch_{prop.to}{nu}^-{alpha}^, we obtain a flat spectral index of = 0:14 0:03 for the AGN core emission, and a steeper index of {alpha}=1.43+/-0.04 and {alpha}=1.15+/-0.04 at positions close to the western and eastern lobes, respectively. The total spectral index is {alpha}=0.92+/-0.02 over the range 73.8MHz-94.5GHz.We detect two CO(2-1) emission lines, both blueshifted with respect to the AGN. Their emission corresponds to two regions, 17kpc southeast and 14kpc southwest of the AGN, not associated with galaxies. In these two regions, we find a total massive molecular gas reservoir of M^tot^_gas_=3.9+/-0.4x10^10^M_{sun}_, which dominates (>~60%) the central total molecular gas reservoir. These results can be explained by massive cool gas flows in the center of the cluster. The AGN early-type host is not yet quenched; its star formation rate is consistent with being on the main sequence of star-forming galaxies in the field (star formation rate ~30-140M_[sun}_/yr), and the cluster core molecular gas reservoir is expected to feed the AGN and the host star formation before quiescence. The other confirmed cluster members show star formation rates at 2 below the field main sequence at similar redshifts and do not have molecular gas masses larger than galaxies of similar stellar mass in the field.
- ID:
- ivo://CDS.VizieR/J/AJ/154/152
- Title:
- CARMA 1 cm spectral line survey of Orion-KL
- Short Name:
- J/AJ/154/152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Orion-KL is a well-known high-mass star-forming region that has long been the target of spectral line surveys and searches for complex molecules. One spectral window where the region had never been surveyed is around wavelengths of {lambda}=1 cm. This is an important window to observe, due to the fundamental and low energy transitions of numerous complex molecules that indicate the maximum spatial extent of the molecular species; knowing the spatial distribution of a molecule aids in determining the formation mechanism(s) of that molecule. Additionally, there are fewer transitions in this window, reducing confusion caused by blended lines that can be very problematic at shorter wavelengths ({lambda}<3 mm). In this work, we present the first spectral line survey at {lambda}=1 cm of the Orion-KL region. A total of 89 transitions were detected from 14 molecular species and isotopologues, and two atomic species. The observations were conducted with the Combined Array for Research in Millimeter-wave Astronomy in both interferometric and single dish modes.
- 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/J/AZh/84/579
- Title:
- Catalog of Class I methanol masers
- Short Name:
- J/AZh/84/579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalog of class I methanol masers discovered so far in the Southern and Northern hemispheres is presented. The catalog contains 160 sources. A statistical analysis shows that, within 2' of the telescope pointing (which corresponds approximately to the field of view of single antennas used in search surveys), 50% of class I methanol masers are associated with objects characteristic of active starforming regions: IRAS sources, ultracompact HII regions, and dense gas dust clouds, as well as OH and H2O interstellar masers. At the same time, bipolar out flows (which could play an active part in pumping the methanol masers) are associated with fewer than 25% of class I methanol masers. In 72% of cases, class I methanol masers are associated with class II methanol maser sources. These results suggest that methanol maser condensations are more appropriately classified by the transition type (that is, the pumping mechanism) than their association with other astronomical objects.
- 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/A+A/515/A42
- Title:
- Catalog of high extinction clouds
- Short Name:
- J/A+A/515/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The earliest phases of massive star formation are found in cold and dense infrared dark clouds (IRDCs). Since the detection method of IRDCs is very sensitive to the local properties of the background emission, we present here an alternative method to search for high column density in the Galactic plane by using infrared extinction maps. We find clouds between 1 and 5kpc, of which many were missed by previous surveys. By studying the physical conditions of a subsample of these clouds, we aim at a better understanding of the initial conditions of massive star formation. We made extinction maps of the Galactic plane based on the 3.6-4.5 microns color excess between the two shortest wavelength Spitzer IRAC bands, reaching to visual extinctions of ~100mag and column densities of 9x10^22^cm^-2^. From this we compiled a new sample of cold and compact high extinction clouds. We used the MAMBO array at the IRAM 30m telescope to study the morphology, masses, and densities of the clouds and the dense clumps within them. The latter were followed up by pointed ammonia observations with the 100m Effelsberg telescope to determine rotational temperatures and kinematic distances. Extinction maps of the Galactic plane trace large scale structures such as the spiral arms. The extinction method probes lower column densities, N(H_2)~4x10^22^cm^-2^, than the 1.2mm continuum, which reaches up to N(H_2)~3x10^23^cm^-2^ but is less sensitive to large scale structures. The 1.2mm emission maps reveal that the high extinction clouds contain extended cold dust emission, from filamentary structures to still diffuse clouds. Most of the clouds are dark in 24 microns, but several show already signs of star formation via maser emission or bright infrared sources, suggesting that the high extinction clouds contain a variety of evolutionary stages. The observations suggest an evolutionary scheme from dark, cold and diffuse clouds, to clouds with a stronger 1.2mm peak and to finally clouds with many strong 1.2mm peaks, which are also warmer, more turbulent, and already have some star formation signposts.
- 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.