- ID:
- ivo://CDS.VizieR/J/MNRAS/335/673
- Title:
- DA white dwarfs in 2dF QSO Redshift Survey
- Short Name:
- J/MNRAS/335/673
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the spectroscopic identification of close to 1000 hydrogen-rich (DA) white dwarfs discovered in the course of the Anglo-Australian 2dF QSO Redshift Survey (2QZ, Cat. <VII/223>). We measured the atmospheric parameters of a subsample of 201 stars based on good-quality Balmer line spectra and we determine the 2QZ population characteristics. Over ten per cent of the sample are potential ZZ Ceti variables. We estimate the DA white dwarf birthrate (b_DA_=0.5-1.0x10^-12^/yr/pc^3^) and the scale-height (h=220-300pc) of the population in the thin disc of the Galaxy by combining information acquired in the Palomar-Green, AAT-UVX and new 2QZ surveys. White dwarfs appear related to G and late-F progenitors. A catalogue of 201 DA white dwarfs is presented.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/758/135
- Title:
- DEEP2 galaxies with UV spectra in the EGS
- Short Name:
- J/ApJ/758/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate galactic-scale outflowing winds in 72 star-forming galaxies at z~1 in the Extended Groth Strip. Galaxies were selected from the DEEP2 survey and follow-up LRIS spectroscopy was obtained covering Si II, C IV, Fe II, Mg II, and Mg I lines in the rest-frame ultraviolet. Using Galaxy Evolution Explorer (GALEX), Hubble Space Telescope (HST), and Spitzer imaging available for the Extended Groth Strip, we examine galaxies on a per-object basis in order to better understand both the prevalence of galactic outflows at z~1 and the star-forming and structural properties of objects experiencing outflows. Gas velocities, measured from the centroids of Fe II interstellar absorption lines, are found to span the interval [-217,+155]km/s. We find that ~40% (10%) of the sample exhibits blueshifted Fe II lines at the 1{sigma} (3{sigma}) level. We also measure maximal outflow velocities using the profiles of the Fe II and Mg II lines; we find that Mg II frequently traces higher velocity gas than Fe II. Using quantitative morphological parameters derived from the HST imaging, we find that mergers are not a prerequisite for driving outflows. More face-on galaxies also show stronger winds than highly inclined systems, consistent with the canonical picture of winds emanating perpendicular to galactic disks. In light of clumpy galaxy morphologies, we develop a new physically motivated technique for estimating areas corresponding to star formation. We use these area measurements in tandem with GALEX-derived star formation rates (SFRs) to calculate SFR surface densities. At least 70% of the sample exceeds an SFR surface density of 0.1M_{sun}_/yr/kpc2, the threshold necessary for driving an outflow in local starbursts. At the same time, the outflow detection fraction of only 40% in Fe II absorption provides further evidence for an outflow geometry that is not spherically symmetric. We see a ~3{sigma} trend between outflow velocity and SFR surface density, but no significant trend between outflow velocity and SFR. Higher resolution data are needed in order to test the scaling relations between outflow velocity and both SFR and SFR surface density predicted by theory.
- ID:
- ivo://CDS.VizieR/J/ApJ/725/2232
- Title:
- Deep NIR survey of the Pipe Nebula. II.
- Short Name:
- J/ApJ/725/2232
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new set of high-resolution dust extinction maps of the nearby and essentially starless Pipe Nebula molecular cloud. The maps were constructed from a concerted deep near-infrared imaging survey with the ESO-VLT, ESO-NTT, CAHA 3.5m telescopes, and 2MASS data. The new maps have a resolution three times higher than the previous extinction map of this cloud by Lombardi et al. (2006A&A...454..781L) and are able to resolve structures down to 2600AU. We detect 244 significant extinction peaks across the cloud. These peaks have masses between 0.1 and 18.4M_{sun}_, diameters between 1.2 and 5.7x10^4^AU (0.06 and 0.28pc), and mean densities of about 10^4^cm^-3^, all in good agreement with previous results. From the analysis of the mean surface density of companions we find a well-defined scale near 1.4x10^4^AU below which we detect a significant decrease in structure of the cloud. This scale is smaller than the Jeans length calculated from the mean density of the peaks. The surface density of peaks is not uniform but instead it displays clustering. Extinction peaks in the Pipe Nebula appear to have a spatial distribution similar to the stars in Taurus, suggesting that the spatial distribution of stars evolves directly from the primordial spatial distribution of high-density material.
- ID:
- ivo://CDS.VizieR/J/A+A/363/62
- Title:
- DENIS galaxies around 16h15m -30deg
- Short Name:
- J/A+A/363/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From a visual inspection of J and K images obtained within the Deep Near Infrared Survey (DENIS) we detected 37 noteworthy galaxies near the galactic plane (|b|<15{deg}). Most of these galaxies are yet uncatalogued. They have either a large dimension (more than 1arcmin in J-band) or a position very close to the galactic plane (|b|<3{deg}). Some of these galaxies are simply not visible on the Digitized Sky Survey. Among them 15 galaxies are suspected to be spirals and could be detected from HI observations. Several large galaxies near the assumed position of the Great Attractor suggests that a concentration of galaxies may be present around the equatorial position: {alpha}_2000_=16h15m, {delta}_2000_=-30{deg}. An inspection of this field from the Digitized Sky Survey and from available 2MASS data confirms the presence of extragalactic structures.
- ID:
- ivo://CDS.VizieR/J/A+A/372/85
- Title:
- Detected sources at 12{mu}m in 47 Tuc
- Short Name:
- J/A+A/372/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present paper investigates the properties of the dust mass loss in stars populating the giant branch of the globular cluster 47 Tuc, by combining ISOCAM and DENIS data. Raster maps of 5 fields covering areas ranging from 4x4 to 15x15arcmin^2^ at different distances from the center of the cluster have been obtained with ISOCAM at 11.5{mu}m (LW10 filter). The covered fields include most of the red variables known in this cluster. A detection threshold of about 0.2 mJy is achieved, allowing us to detect giant stars at 11.5{mu}m all the way down to the horizontal branch. No dust-enshrouded asymptotic giant branch stars have been found in the observed fields, contrary to the situation encountered in LMC/SMC globular clusters with larger turnoff masses. The color index [12]-[2] (based on the ISO 11.5{mu}m flux and on the DENIS K_S_ magnitude) is used as a diagnostic of dust emission (and hence dust mass loss). Its evolution with luminosity along the giant branch reveals that dust mass loss is only present in V3 (the only cluster Mira variable observed in the present study) and in V18, a star presenting intermittent variability. This conclusion confirms the importance of stellar pulsations in the dust formation and ensuing mass loss.
- ID:
- ivo://CDS.VizieR/J/ApJ/791/35
- Title:
- Detection of 715 Kepler planet candidates host stars
- Short Name:
- J/ApJ/791/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Robo-AO Kepler Planetary Candidate Survey is observing every Kepler planet candidate host star with laser adaptive optics imaging to search for blended nearby stars, which may be physically associated companions and/or responsible for transit false positives. In this paper, we present the results from the 2012 observing season, searching for stars close to 715 Kepler planet candidate hosts. We find 53 companions, 43 of which are new discoveries. We detail the Robo-AO survey data reduction methods including a method of using the large ensemble of target observations as mutual point-spread-function references, along with a new automated companion-detection algorithm designed for large adaptive optics surveys. Our survey is sensitive to objects from ~ 0.15'' to 2.5'' separation, with magnitude differences up to {Delta}m ~ 6. We measure an overall nearby-star probability for Kepler planet candidates of 7.4%+/-1.0%, and calculate the effects of each detected nearby star on the Kepler-measured planetary radius. We discuss several Kepler Objects of Interest (KOIs) of particular interest, including KOI-191 and KOI-1151, which are both multi-planet systems with detected stellar companions whose unusual planetary system architecture might be best explained if they are "coincident multiple" systems, with several transiting planets shared between the two stars. Finally, we find 98% confidence evidence that short-period giant planets are two to three times more likely than longer-period planets to be found in wide stellar binaries.
- ID:
- ivo://CDS.VizieR/J/A+A/373/576
- Title:
- Detection of Tycho variables stars
- Short Name:
- J/A+A/373/576
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an original way to detect variable stars in the Tycho photometric observations. A modified Kolmogorov-Smirnov statistical test has been constructed, based on a model of most of the satellite's parameters, leading to the dispersion in the measurements. This allows us to build a treatment taking into account truncated detections and censored measurements, and to search for variability in the faint part of the catalogue. The selection threshold of variable stars has been calibrated to minimize false alarm rate. Reliable results were thus obtained for stars as faint as 11 mag. One thousand and ninety-one suspected variable stars have been listed, 407 of which are already known in Hipparcos, GCVS or NSV, and 684 of which are suspected variable stars to be identified soon.
- ID:
- ivo://CDS.VizieR/J/ApJ/697/1138
- Title:
- Discovery of PNe in M82
- Short Name:
- J/ApJ/697/1138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using an [OIII]{lambda}5007 on-band/off-band filter technique, we identify 109 planetary nebulae (PNe) candidates in the edge-on spiral galaxy M 82, using the FOCAS instrument at the 8.2m Subaru Telescope. The use of ancillary high-resolution Hubble Space Telescope Advanced Camera for Surveys H{alpha} imaging aided in confirming these candidates, helping to discriminate PNe from contaminants such as supernova remnants and compact HII regions. Once identified, these PNe reveal a great deal about the host galaxy; our analysis covers kinematics, stellar distribution, and distance determination. Radial velocities were determined for 94 of these PNe using a method of slitless spectroscopy, from which we obtain a clear picture of the galaxy's rotation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/492/L40
- Title:
- Disentangling cataclysmic variables in Gaia DR2
- Short Name:
- J/MNRAS/492/L40
- Date:
- 07 Dec 2021 09:36:41
- Publisher:
- CDS
- Description:
- Cataclysmic Variables (CVs) are interacting binaries consisting of at least three components that control their colour and magnitude. Using Gaia we here investigate the influence of the physical properties of these binaries on their position in the Hertzsprung-Russell diagram (HR-diagram). The CVs are on average located between the main sequence and the white dwarf regime, the maximum density being at G_BP_-G_RP_~=0.56 and G_abs_~10.15. We nd a trend of the orbital period with colour and absolute brightness: with decreasing period, the CVs become bluer and fainter. We also identify the location of the various CV sub-types in the HR-diagram and discuss the possible location of detached CVs, going through the orbital period gap.
- ID:
- ivo://CDS.VizieR/J/A+A/478/507
- Title:
- Distances and atmospheric parameters of MSU stars
- Short Name:
- J/A+A/478/507
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent analyses of low-mass eclipsing binary stars have unveiled a significant disagreement between the observations and the predictions of stellar structure models. Results show that theoretical models underestimate the radii and overestimate the effective temperatures of low-mass stars but yield luminosities that accord with observations. A hypothesis based upon the effects of stellar activity was put forward to explain the discrepancies. Here we study the existence of the same trend in single active stars and provide a consistent scenario to explain systematic differences between active and inactive stars in the H-R diagram reported earlier. The analysis is done using single field stars of spectral types late-K and M and computing its bolometric magnitudes and temperatures through infrared colours and spectral indices. The properties of the stars in samples of active and inactive stars are compared statistically to reveal systematic differences. After accounting for a number of possible bias effects, active stars are shown to be cooler than inactive stars of similar luminosity therefore implying a larger radius as well, in proportions that are in excellent agreement with those found from eclipsing binaries. The present results generalise the existence of strong radius and temperature dependences on stellar activity to the entire population of low-mass stars, regardless of their membership in close binary systems.
