- ID:
- ivo://CDS.VizieR/J/ApJS/152/81
- Title:
- CO survey toward starless cores
- Short Name:
- J/ApJS/152/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A CO survey is undertaken toward about 80% of the starless cores in the Lee & Myers catalog that can be observed in the northern hemisphere to investigate their general observational properties such as line width and intensity, from which one can deduce their environmental physical conditions. The peak ^12^CO intensity implies a kinetic temperature close to 10K, as is already known, but for some of the cores the kinetic temperature is much higher than 10K, suggesting either that they are not really starless or that they are externally heated. We derive the ratios of peak intensities and line widths for the pairs of ^12^CO and ^13^CO lines and find a value of ~1.7 for both. The linear correlations between them are most likely to be due to clumpy structure. These data are also compared with data sets of CS 2-1 and N_2_H^+^ 1-0 lines tracing high-density regions. It is found that the peak intensity and line width of ^13^CO are roughly correlated with those of CS, suggesting that the outer envelope is kinematically related to the inner dense core. Confirming that the ^12^CO lines seldom exhibit deep self-reversal features, whereas this is not unusual for the CS lines, we propose a heuristic model where the outer part is clumpy, but the inner part has a rather smooth density profile, with a uniform temperature and mean density decreasing outward. We apply three-dimensional radiative transfer calculations to this simple model, demonstrating that the essential observational features of the starless cores are successfully reproduced.
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- ID:
- ivo://CDS.VizieR/J/ApJ/669/821
- Title:
- CO Tully-Fisher relation for host galaxies of QSOs
- Short Name:
- J/ApJ/669/821
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The integrated line width derived from CO spectroscopy provides a powerful tool to study the internal kinematics of extragalactic objects, including quasars at high redshift, provided that the observed line width can be properly translated to more conventionally used kinematical parameters of galaxies. We show, through the construction of a Ks-band CO Tully-Fisher relation for nearby galaxies spanning a wide range in infrared luminosity, that the CO line width measured at 20% of the peak intensity, when corrected for inclination and other effects, successfully recovers the maximum rotation velocity of the disk. The line width at 50% of the peak intensity performs much more poorly, in large part because CO lines have a wide range of profiles, which are shown to vary systematically with infrared luminosity. We present a practical prescription for converting observed CO line widths into the stellar velocity dispersion of the bulge ({sigma}*) and then apply it to a sample of low-redshift (z<~0.2) and high-redshift (1.4<~z<~6.4) quasars to study their host galaxies.
- ID:
- ivo://CDS.VizieR/J/A+AS/118/381
- Title:
- COU 247, ADS 3672 & ADS 15182 observations
- Short Name:
- J/A+AS/118/381
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents new orbits for two visual double stars COU 247 (CCDM 00095+1907) and ADS 3672 (STT 95, CCDM 05055+1948) and a revised orbit for ADS 15182 (A 772, CCDM 21395+3009) computed by the Thiele-van den Bos method.
- ID:
- ivo://CDS.VizieR/J/MNRAS/459/1170
- Title:
- Coulour-Period relation for Cepheids
- Short Name:
- J/MNRAS/459/1170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare mid-infrared (IR) 3.6 and 4.5{mu}m Warm Spitzer observations for Cepheids in the Milky Way and the Large and Small Magellanic Clouds. Using models, we explore in detail the effect of the CO rotation-vibration band-head at 4.6{mu}m on the mid-IR photometry. We confirm the temperature sensitivity of the CO band-head at 4.6{mu}m and find no evidence for an effect at 3.6{mu}m. We compare the ([3.6]-[4.5]) period-colour relations in the MW, LMC and SMC. The slopes of the period-colour relations for the three galaxies are in good agreement, but there is a trend in zero-point with metallicity, with the lowest metallicity Cepheids having redder mid-IR colours. Finally, we present a colour-[Fe/H] relation based on published spectroscopic metallicities. This empirical relation, calibrated to the metallicity system of Genovali et al., demonstrates that the ([3.6]-[4.5]) colour provides a reliable metallicity indicator for Cepheids, with a precision comparable to current spectroscopic determinations.
- ID:
- ivo://CDS.VizieR/J/ApJ/848/L16
- Title:
- Counterpart of GW170817. I. DECam obs.
- Short Name:
- J/ApJ/848/L16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Dark Energy Camera (DECam) discovery of the optical counterpart of the first binary neutron star merger detected through gravitational-wave emission, GW170817. Our observations commenced 10.5hr post-merger, as soon as the localization region became accessible from Chile. We imaged 70deg^2^ in the i and z bands, covering 93% of the initial integrated localization probability, to a depth necessary to identify likely optical counterparts (e.g., a kilonova). At 11.4hr post-merger we detected a bright optical transient located 10.6" from the nucleus of NGC 4993 at redshift z=0.0098, consistent (for H_0_=70km/s/Mpc) with the distance of 40+/-8Mpc reported by the LIGO Scientific Collaboration and the Virgo Collaboration (LVC). At detection the transient had magnitudes of i=17.3 and z=17.4, and thus an absolute magnitude of Mi=-15.7, in the luminosity range expected for a kilonova. We identified 1500 potential transient candidates. Applying simple selection criteria aimed at rejecting background events such as supernovae, we find the transient associated with NGC 4993 as the only remaining plausible counterpart, and reject chance coincidence at the 99.5% confidence level. We therefore conclude that the optical counterpart we have identified near NGC 4993 is associated with GW170817. This discovery ushers in the era of multi-messenger astronomy with gravitational waves and demonstrates the power of DECam to identify the optical counterparts of gravitational-wave sources.
- ID:
- ivo://CDS.VizieR/J/ApJS/203/15
- Title:
- Counterparts to 1.4GHz sources in ECDF-S
- Short Name:
- J/ApJS/203/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a sample of 883 sources detected in a deep Very Large Array survey at 1.4GHz in the Extended Chandra Deep Field South. This paper focuses on the identification of their optical and infrared (IR) counterparts. We use a likelihood-ratio technique that is particularly useful when dealing with deep optical images to minimize the number of spurious associations. We find a reliable counterpart for 95% of our radio sources. Most of the counterparts (74%) are detected at optical wavelengths, but there is a significant fraction (21%) that are only detectable in the IR. Combining newly acquired optical spectra with data from the literature, we are able to assign a redshift to 81% of the identified radio sources (37% spectroscopic). We also investigate the X-ray properties of the radio sources using the Chandra 4Ms and 250ks observations. In particular, we use a stacking technique to derive the average properties of radio objects undetected in the Chandra images. The results of our analysis are collected in a new catalog containing the position of the optical/IR counterpart, the redshift information, and the X-ray fluxes. It is the deepest multi-wavelength catalog of radio sources, which will be used for future study of this galaxy population.
- ID:
- ivo://CDS.VizieR/J/A+A/461/631
- Title:
- Counterparts to massive X-ray binaries
- Short Name:
- J/A+A/461/631
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The X-ray and gamma-ray observatory INTEGRAL has discovered large numbers of new hard X-ray sources, many of which are believed to be high mass X-ray binaries. However, for a significant fraction, their counterparts remain unidentified. We explore the use of photometric catalogues to find optical counterparts to high mass X-ray binaries and search for objects likely to be early-type stars within the error circles of several INTEGRAL sources. ************************************************************************** * * * Sorry, but the author(s) never supplied the tabular material * * announced in the paper * * * **************************************************************************
- ID:
- ivo://CDS.VizieR/J/ApJ/405/498
- Title:
- Counts and spectral indices at 8.44GHz
- Short Name:
- J/ApJ/405/498
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the VLA to make deep images of two 7x7' fields at 8.44 GHz with 10" resolution. With an rms noise of 3.2 and 5.1 {micro}Jy, respectively, in the two fields, we compiled a catalog of 82 sources. The normalized differential 8.44 GHz counts are similar to those at 1.41 and 4.86 GHz. All show a similarly steep submillijansky slope, which is only somewhat flatter than that expected for a nonevolving Euclidean population ({gamma}=2.5). Microjansky radio sources at 4.86 GHz have been identified with faint blue galaxies (18<~V<~28 mag). We argue that their expected median redshift is about 0.5-0.75. Hence, cosmological evolution may be needed to explain the steep slope of the microjansky counts. The 8.44 GHz counts must converge with slope {gamma}<2.0 below S(8.44)~300 nJy, or they would exceed the available field galaxy counts down to V~28 mag, and they must permanently converge below S(8.44)~20 nJy, or their integrated sky brightness would distort the observed thermal cosmic background radiation spectrum at centimeter wavelengths. The estimated 31.5 GHz sky brightness from nanojansky to jansky levels is <36 {micro}K (3{sigma}). Even if weak radio sources cluster on scales of degrees as faint galaxies do, their anisotropic contribution to the COBE DMR experiment (with 7deg FWHM-beam) would not exceed ~1.2{micro}K.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A1
- Title:
- Coupling factors of 5166 KIC
- Short Name:
- J/A+A/600/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The power of asteroseismology relies on the capability of global oscillations to infer the stellar structure. For evolved stars, we benefit from unique information directly carried out by mixed modes that probe their radiative cores. This third article of the series devoted to mixed modes in red giants focuses on their coupling factors, which have remained largely unexploited up to now. With the measurement of coupling factors, we intend to give physical constraints on the regions surrounding the radiative core and the hydrogen-burning shell of subgiants and red giants. A new method for measuring the coupling factor of mixed modes was implemented, which was derived from the method recently implemented for measuring period spacings. This new method was automated so that it could be applied to a large sample of stars. Coupling factors of mixed modes were measured for thousands of red giants. They show specific variation with mass and evolutionary stage. Weak coupling is observed for the most evolved stars on the red giant branch only; large coupling factors are measured at the transition between subgiants and red giants as well as in the red clump. The measurement of coupling factors in dipole mixed modes provides a new insight into the inner interior structure of evolved stars. While the large frequency separation and the asymptotic period spacings probe the envelope and core, respectively, the coupling factor is directly sensitive to the intermediate region in between and helps determine its extent. Observationally, the determination of the coupling factor is a prior to precise fits of the mixed-mode pattern and can now be used to address further properties of the mixed-mode pattern, such as the signature of buoyancy glitches and core rotation.
- ID:
- ivo://CDS.VizieR/J/ApJS/160/319
- Title:
- COUP: observations and source lists
- Short Name:
- J/ApJS/160/319
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a description of the data reduction methods and the derived catalog of more than 1600 X-ray point sources from the exceptionally deep 2003 January Chandra X-Ray Observatory (Chandra) observation of the Orion Nebula Cluster and embedded populations around OMC-1. The observation was obtained with Chandra's Advanced CCD Imaging Spectrometer (ACIS) and has been nicknamed the Chandra Orion Ultradeep Project (COUP). With an 838ks exposure made over a continuous period of 13.2 days, the COUP observation provides the most uniform and comprehensive data set on the X-ray emission of normal stars ever obtained in the history of X-ray astronomy.
