- ID:
- ivo://CDS.VizieR/J/AJ/132/1221
- Title:
- VJHK and SDSS photometry of DA white dwarfs
- Short Name:
- J/AJ/132/1221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have calibrated four major ground-based photometric systems with respect to the Hubble Space Telescope (HST) absolute flux scale, which is defined by Vega and four fundamental DA white dwarfs. These photometric systems include the Johnson-Kron-Cousins UBVRI, the Stroemgren uvby filters, the Two Micron All Sky Survey JHKs, and the Sloan Digital Sky Survey ugriz filters. Synthetic magnitudes are calculated from model white dwarf spectra folded through the published filter response functions; these magnitudes in turn are absolutely calibrated with respect to the HST flux scale. Effective zero-magnitude fluxes and zero-point offsets of each system are determined. In order to verify the external observational consistency, as well as to demonstrate the applicability of these definitions, the synthetic magnitudes are compared with the respective observed magnitudes of larger sets of DA white dwarfs that have well-determined effective temperatures and surface gravities and span a wide range in both of these parameters.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/802/69
- Title:
- VLA, ALMA and SMA monitoring of Sgr A*
- Short Name:
- J/ApJ/802/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report new observations with the Very Large Array, Atacama Large Millimeter Array, and Submillimeter Array at frequencies from 1.0 to 355GHz of the Galactic Center black hole, Sagittarius A*. These observations were conducted between 2012 October and 2014 November. While we see variability over the whole spectrum with an amplitude as large as a factor of 2 at millimeter wavelengths, we find no evidence for a change in the mean flux density or spectrum of Sgr A* that can be attributed to interaction with the G2 source. The absence of a bow shock at low frequencies is consistent with a cross-sectional area for G2 that is less than 2x10^29^cm2. This result fits with several model predictions including a magnetically arrested cloud, a pressure-confined stellar wind, and a stellar photosphere of a binary merger. There is no evidence for enhanced accretion onto the black hole driving greater jet and/or accretion flow emission. Finally, we measure the millimeter wavelength spectral index of Sgr A* to be flat; combined with previous measurements, this suggests that there is no spectral break between 230 and 690GHz. The emission region is thus likely in a transition between optically thick and thin at these frequencies and requires a mix of lepton distributions with varying temperatures consistent with stratification.
- ID:
- ivo://CDS.VizieR/J/A+A/453/911
- Title:
- VLA and IR observations of the S235A-B region
- Short Name:
- J/A+A/453/911
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on new aspects of the star-forming region S235AB revealed through high-resolution observations at radio and mid-infrared wavelengths. Using the Very Large Array, we carried out sensitive observations of S235AB in the cm continuum (6, 3.6, 1.3, and 0.7) and in the 22GHz water maser line. These were complemented with Spitzer Space Telescope Infrared Array Camera archive data to clarify the correspondence between radio and IR sources. We made also use of newly presented data from the Medicina water maser patrol, started in 1987, to study the variability of the water masers found in the region.
20944. VLA and XMM-EPIX maps of M83
- ID:
- ivo://CDS.VizieR/J/A+A/640/A109
- Title:
- VLA and XMM-EPIX maps of M83
- Short Name:
- J/A+A/640/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Reconnection heating has been considered as a potential source of the heating of the interstellar medium. In some galaxies, significant polarised radio emission has been found between the spiral arms. This emission has a form of 'magnetic arms' that resembles the spiral structure of the galaxy. Reconnection effects could convert some of the energy of the turbulent magnetic field into the thermal energy of the surrounding medium, leaving more ordered magnetic fields, as is observed in the magnetic arms. Sensitive radio and X-ray data for the grand-design spiral galaxy M 83 are used for a detailed analysis of the possible interactions of magnetic fields with hot gas, including a search for signatures of gas heating by magnetic reconnection effects. Magnetic field strengths and energies derived from the radio emission are compared with the parameters of the hot gas calculated from the model fits to sensitive X-ray spectra of the hot gas emission. The available X-ray data allowed us to distinguish two thermal components in the halo of M 83. We found slightly higher average temperatures of the hot gas in the interarm regions, which results in higher energies per particle and is accompanied by a decrease in the energy density of the magnetic fields. The observed differences in the energy budget between the spiral arms and the interarm regions suggest that, similar to the case of another spiral galaxy NGC 6946, we may be observing hints for gas heating by magnetic reconnection effects in the interarm regions. These effects, which act more efficiently on the turbulent component of the magnetic field, are expected to be stronger in the spiral arms. However, with the present data it is only possible to trace them in the interarm regions, where the star formation and the resulting turbulence is low.
- ID:
- ivo://CDS.VizieR/J/ApJS/219/41
- Title:
- VLA & Chandra obs. of IRAS20126+4104 region
- Short Name:
- J/ApJS/219/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from Chandra ACIS-I and Karl G. Jansky Very Large Array 6cm continuum observations of the IRAS 20126+4104 massive star-forming region. We detect 150 X-ray sources within the 17'x17' ACIS-I field, and a total of 13 radio sources within the 9.2' primary beam at 4.9GHz. Among these observations are the first 6cm detections of the central sources reported by Hofner et al. (2007A&A...465..197H), namely, I20N1, I20S, and I20var. A new variable radio source is also reported. Searching the 2MASS archive, we identified 88 near-infrared (NIR) counterparts to the X-ray sources. Only four of the X-ray sources had 6cm counterparts. Based on an NIR color-color analysis and on the Besancon simulation of Galactic stellar populations, we estimate that approximately 80 X-ray sources are associated with this massive star-forming region. We detect an increasing surface density of X-ray sources toward the massive protostar and infer the presence of a cluster of at least 43 young stellar objects within a distance of 1.2pc from the massive protostar.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A1
- Title:
- VLA-COSMOS 3 GHz Large Project
- Short Name:
- J/A+A/602/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the VLA-COSMOS 3GHz Large Project based on 384 hours of observations with the Karl G. Jansky Very Large Array (VLA) at 3GHz (10cm) toward the two square degree Cosmic Evolution Survey (COSMOS) field. The final mosaic reaches a median rms of 2.3 uJy/beam over the two square degrees at an angular resolution of 0.75". To fully account for the spectral shape and resolution variations across the broad (2GHz) band, we image all data with a multiscale, multifrequency synthesis algorithm. We present a catalog of 10,830 radio sources down to 5{sigma}, out of which 67 are combined from multiple components. Comparing the positions of our 3GHz sources with those from the Very Long Baseline Array (VLBA)-COSMOS survey, we estimate that the astrometry is accurate to 0.01" at the bright end (signal-to-noise ratio, S/N_3GHz_>20). Survival analysis on our data combined with the VLA-COSMOS 1.4GHz Joint Project catalog yields an expected median radio spectral index of {alpha}=-0.7. We compute completeness corrections via Monte Carlo simulations to derive the corrected 3GHz source counts. Our counts are in agreement with previously derived 3GHz counts based on single-pointing (0.087 square degrees) VLA data. In summary, the VLA-COSMOS 3GHz Large Project simultaneously provides the largest and deepest radio continuum survey at high (0.75") angular resolution to date, bridging the gap between last-generation and next-generation surveys.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A2
- Title:
- VLA-COSMOS 3 GHz Large Project. II.
- Short Name:
- J/A+A/602/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the composition of the faint radio population selected from the VLA-COSMOS 3GHz Large Project, a radio continuum survey performed at 10 cm wavelength. The survey covers a 2.6 square degree area with a mean rms of ~2.3uJy/beam, cataloging 10,830 sources above 5sigma, and enclosing the full 2 square degree COSMOS field. By combining these radio data with optical, near-infrared (UltraVISTA), and mid-infrared (Spitzer/IRAC) data, as well as X-ray data (Chandra), we find counterparts to radio sources for ~93% of the total radio sample (in the unmasked areas of the COSMOS field, i.e., those not affected by saturated or bright sources in the optical to NIR bands), reaching out to z~6. We further classify the sources as star forming galaxies or AGN based on various criteria, such as X-ray luminosity, observed MIR color, UV-FIR spectral-energy distribution, rest-frame NUV-optical color corrected for dust extinction, and radio-excess relative to that expected from the hosts' star-formation rate. We separate the AGN into sub-samples dominated by low-to-moderate and moderate-to-high radiative luminosity AGN, candidates for high- redshift analogues to local low- and high-excitation emission line AGN, respectively. We study the fractional contributions of these sub-populations down to radio flux levels of ~11uJy at 3GHz (or ~20uJy at 1.4GHz assuming a spectral index of -0.7). We find that the dominant fraction at 1.4GHz flux densities above ~200uJy is constituted of low-to-moderate radiative luminosity AGN. Below densities of ~100uJy the fraction of star-forming galaxies increases to ~60%, followed by the moderate-to-high radiative luminosity AGN (~20%), and low-to-moderate radiative luminosity AGN (~20%). Based on this observational evidence, we extrapolate the fractions down to sensitivities of the Square Kilometer Array (SKA). Our estimates suggest that at the faint flux limits to be reached by the (Wide, Deep, and UltraDeep) SKA1 surveys, a selection based only on radio flux limits can provide a simple tool to efficiently identify samples highly (>75%) dominated by star-forming galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/621/A139
- Title:
- VLA-COSMOS 3GHz sources average radio SED
- Short Name:
- J/A+A/621/A139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct the average radio spectral energy distribution (SED) of highly star-forming galaxies (HSFGs) up to z~4. Infrared and radio luminosities are bound by a tight correlation that is defined by the so-called q parameter. This infrared-radio correlation provides the basis for the use of radio luminosity as a star-formation tracer. Recent stacking and survival analysis studies find q to be decreasing with increasing redshift. It was pointed out that a possible cause of the redshift trend could be the computation of rest-frame radio luminosity via a single power-law assumption of the star-forming galaxies' (SFGs) SED. To test this, we constrained the shape of the radio SED of a sample of HSFGs. To achieve a broad rest-frame frequency range, we combined previously published Very Large Array observations of the COSMOS field at 1.4GHz and 3GHz with unpublished Giant Meterwave Radio Telescope (GMRT) observations at 325MHz and 610MHz by employing survival analysis to account for non-detections in the GMRT maps. We selected a sample of HSFGs in a broad redshift range (z{in}[0.3,4], SFR>=100M_{sun}_/yr) and constructed the average radio SED. By fitting a broken power-law, we find that the spectral index changes from {sigma}_1_=0.42+/-0.06 below a rest-frame frequency of 4.3GHz to {sigma}_2_=0.94+/-0.06 above 4.3GHz. Our results are in line with previous low-redshift studies of HSFGs (SFR>10M_{sun}_/yr) that show the SED of HSFGs to differ from the SED found for normal SFGs (SFR<10M_{sun}}/yr). The difference is mainly in a steeper spectrum around 10GHz, which could indicate a smaller fraction of thermal free-free emission. Finally, we also discuss the impact of applying this broken power-law SED in place of a simple power-law in K-corrections of HSFGs and a typical radio SED for normal SFGs drawn from the literature. We find that the shape of the radio SED is unlikely to be the root cause of the q-z trend in SFGs.
20949. VLA-COSMOS survey. II.
- ID:
- ivo://CDS.VizieR/J/ApJS/172/46
- Title:
- VLA-COSMOS survey. II.
- Short Name:
- J/ApJS/172/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VLA-COSMOS Large Project is described and its scientific objective is discussed. We present a catalog of 3600 radio sources found in the 2deg^2^ COSMOS field at 1.4GHz. The observations in the VLA A and C configuration resulted in a resolution of 1.5"x1.4" and a mean rms noise of ~10.5(15)uJy/beam in the central 1(2)deg^2^. Eighty radio sources are clearly extended consisting of multiple components, and most of them appear to be double-lobed radio galaxies. The astrometry of the catalog has been thoroughly tested, and the uncertainty in the relative and absolute astrometry are 130 and <55mas, respectively.
20950. V360 Lac spectroscopy
- ID:
- ivo://CDS.VizieR/J/A+A/455/1037
- Title:
- V360 Lac spectroscopy
- Short Name:
- J/A+A/455/1037
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We include existing photometric and spectroscopic material with new observations in a detailed study of the Be+F binary V360 Lac. We used the programs FOTEL and KOREL to derive an improved linear ephemeris and to disentangle the line profiles of both binary components and telluric lines. The BINSYN software suite (described in the paper) is used to calculate synthetic light curves and spectra to fit the UBV photometry, an IUE spectrum, blue and red ground-based spectra, and observed radial-velocity curves.
