- ID:
- ivo://CDS.VizieR/J/AJ/160/186
- Title:
- Gaia survey of stars associated with Lupus Clouds
- Short Name:
- J/AJ/160/186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I have used high-precision photometry and astrometry from the second data release of the Gaia mission to perform a survey for young stars associated with the Lupus clouds, which have distances of ~160pc and reside within the Scorpius-Centaurus (Sco-Cen) OB association. The Gaia data have made it possible to distinguish Lupus members from most of the stars in other groups in Sco-Cen that overlap with the Lupus clouds, which have contaminated previous surveys. The new catalog of candidate Lupus members should be complete for spectral types earlier than M7 at AK<0.2 within fields encompassing clouds 1-4. I have used that catalog to characterize various aspects of the Lupus stellar population. For instance, the sequence of low- mass stars in Lupus is ~0.4mag brighter than the sequence for Upper Sco, which implies an age of ~6Myr based an adopted age of 10-12Myr for Upper Sco and the change in luminosity with age predicted by evolutionary models. I also find that the initial mass function in Lupus is similar to that in other nearby star-forming regions based on a comparison of their distributions of spectral types.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/899/140
- Title:
- 632 Gaia Ultracompact Dwarf galaxy candidates
- Short Name:
- J/ApJ/899/140
- Date:
- 14 Mar 2022 00:54:57
- Publisher:
- CDS
- Description:
- Tidally stripped galaxy nuclei and luminous globular clusters (GCs) are important tracers of the halos and assembly histories of nearby galaxies, but are difficult to reliably identify with typical ground-based imaging data. In this paper we present a new method to find these massive star clusters using Gaia DR2, focusing on the massive elliptical galaxy Centaurus A (Cen A). We show that stripped nuclei and GCs are partially resolved by Gaia at the distance of Cen A, showing characteristic astrometric and photometric signatures. We use this selection method to produce a list of 632 new candidate luminous clusters in the halo of Cen A out to a projected radius of 150kpc. Adding in broadband photometry and visual examination improves the accuracy of our classification. In a spectroscopic pilot program we have confirmed five new luminous clusters, which includes the 7th and 10th most luminous GC in Cen A. Three of the newly discovered GCs are further away from Cen A than all previously known GCs. Several of these are compelling candidates for stripped nuclei. We show that our novel Gaia selection method retains at least partial utility out to distances of ~25Mpc and hence is a powerful tool for finding and studying star clusters in the sparse outskirts of galaxies in the local universe.
- ID:
- ivo://CDS.VizieR/J/MNRAS/497/130
- Title:
- Gaia white dwarfs within 40pc. I
- Short Name:
- J/MNRAS/497/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic survey of 230 white dwarf candidates within 40pc of the Sun from the William Herschel Telescope and Gran Telescopio Canarias. All candidates were selected from Gaia Data Release 2 (DR2) and in almost all cases, had no prior spectroscopic classifications. We find a total of 191 confirmed white dwarfs and 39 main-sequence star contaminants. The majority of stellar remnants in the sample are relatively cool (<Teff>=6200K), showing either hydrogen Balmer lines or a featureless spectrum, corresponding to 89 DA and 76 DC white dwarfs, respectively. We also recover two DBA white dwarfs and 9-10 magnetic remnants. We find two carbon-bearing DQ stars and 14 new metal-rich white dwarfs. This includes the possible detection of the first ultra-cool white dwarf with metal lines. We describe three DZ stars for which we find at least four different metal species, including one that is strongly Fe- and Ni-rich, indicative of the accretion of a planetesimal with core-Earth composition. We find one extremely massive (1.31+/-0.01M_{sun}_) DA white dwarf showing weak Balmer lines, possibly indicating stellar magnetism. Another white dwarf shows strong Balmer line emission but no infrared excess, suggesting a low-mass sub-stellar companion. A high spectroscopic completeness (>99 per cent) has now been reached for Gaia DR2 sources within 40-pc sample, in the Northern hemisphere ({delta}>0{deg} and located on the white dwarf cooling track in the Hertzsprung-Russell diagram. A statistical study of the full northern sample is presented in a companion paper (McCleery et al., Paper II, 2020MNRAS.499.1890M, Cat. J/MNRAS/499/1890).
- ID:
- ivo://CDS.VizieR/J/MNRAS/499/1890
- Title:
- Gaia white dwarfs within 40pc. II.
- Short Name:
- J/MNRAS/499/1890
- Date:
- 14 Jan 2022 00:10:10
- Publisher:
- CDS
- Description:
- We present an overview of the sample of northern hemisphere white dwarfs within 40pc of the Sun detected from Gaia Data Release 2 (DR2). We find that 521 sources are spectroscopically confirmed degenerate stars, 111 of which were first identified as white dwarf candidates from Gaia DR2 and followed-up recently with the William Herschel Telescope and Gran Telescopio Canarias. Three additional white dwarf candidates remain spectroscopically unobserved and six unresolved binaries are known to include a white dwarf but were not in our initial selection in the Gaia DR2 Hertzsprung-Russell diagram (HRD). Atmospheric parameters are calculated from Gaia and Pan-STARRS photometry for all objects in the sample, confirming most of the trends previously observed in the much smaller 20pc sample. Local white dwarfs are overwhelmingly consistent with Galactic disc kinematics, with only four halo candidates. We find that DAZ white dwarfs are significantly less massive than the overall DA population (MDAZ_avg_=0.59M_{sun}_, MDA_avg_=0.66M_{sun}_). It may suggest that planet formation is less efficient at higher mass stars, producing more massive white dwarfs. We detect a sequence of crystallised white dwarfs in the mass range from 0.6<=M/M_{sun}_<=1.0 and find that the vast majority of objects on the sequence have standard kinematic properties that correspond to the average of the sample, suggesting that their nature can be explained by crystallisation alone. We also detect 26 double degenerates and white dwarf components in 56 wide binary systems.
- ID:
- ivo://CDS.VizieR/J/A+A/392/491
- Title:
- Galactic abundance gradient. III.
- Short Name:
- J/A+A/392/491
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As a continuation of our previous work, which concerned the radial abundance distribution in the galactic disc over the distances 4-10kpc this paper presents the first results on the metallicity in the outer disc (R_G_>10kpc). Based on high-resolution spectra obtained for 19 distant Cepheids we sampled galactocentric distances from 10 to 12 kpc. Combined with the results of our previous work on the inner and middle parts of the galactic disc, the present data enable one to study the structure of the radial abundance distribution over a large baseline. In particular, we find indications of a discontinuity in the radial abundance distribution for iron as well as a number of the other elements. The discontinuity is seen at a galactocentric distance R_G_=10kpc. This finding supports the results reported earlier by Twarog et al. (1997AJ....114.2556T).
- ID:
- ivo://CDS.VizieR/J/A+A/413/159
- Title:
- Galactic abundance gradient. V.
- Short Name:
- J/A+A/413/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports on the spectroscopic investigation of 12 Cepheids which are situated in the crucial region of galactocentric distances from 9kpc to 12kpc, where according to our previous results (Andrievsky et al., 2002, Cat. <J/A+A/392/491>; Luck et al., 2003A&A...401..939L) the radial metallicity distribution experiences an obvious change. In particular, the wriggle in the iron abundance distribution is found to fall approximately at galactocentric distances 10-11kpc (assuming galactocentric distance of the Sun kpc). Within the transition zone from 10 to 11kpc the relative-to-solar iron abundance decreases approximately to -0.2dex. The new sample of stars, analyzed in present paper, gives results supporting the previous conclusion about the multimodal character of the metallicity distribution in galactic disc. Using a quite simple consideration of galactic chemical evolution we show that the observed distribution can be explained in the framework of a model which includes the spiral arms. In particular, the wriggle feature associated with 11 kpc can be interpreted as a change of metallicity level in the vicinity of the galactic corotation resonance.
- ID:
- ivo://CDS.VizieR/VIII/100
- Title:
- GaLactic and Extragalactic All-sky MWA survey
- Short Name:
- VIII/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Murchison Widefield Array (MWA), the low-frequency Square Kilometre Array (SKA1 LOW) precursor located in Western Australia, we have completed the GaLactic and Extragalactic All-sky MWA (GLEAM) survey, and present the resulting extragalactic catalogue, utilising the first year of observations. The catalogue covers 24,402 square degrees, over declinations south of +30{deg} and Galactic latitudes outside 10{deg} of the Galactic plane, excluding some areas such as the Magellanic Clouds. It contains 307,456 radio sources with 20 separate flux density measurements across 72-231MHz, selected from a time- and frequency- integrated image centred at 200MHz, with a resolution of ~=2'. Over the catalogued region, we estimate that the catalogue is 90% complete at 170mJy, and 50% complete at 55mJy, and large areas are complete at even lower flux density levels. Its reliability is 99.97% above the detection threshold of 5{sigma}, which itself is typically 50mJy. These observations constitute the widest fractional bandwidth and largest sky area survey at radio frequencies to date, and calibrate the low frequency flux density scale of the southern sky to better than 10%. This paper presents details of the flagging, imaging, mosaicking, and source extraction/characterisation, as well as estimates of the completeness and reliability. All source measurements and images are available online. This is the first in a series of publications describing the GLEAM survey results.
- ID:
- ivo://nasa.heasarc/gleamegcat
- Title:
- GaLactic and Extragalactic All-sky MWA Survey (GLEAM) Extragalactic Catalog
- Short Name:
- GLEAMEGCAT
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- Using the Murchison Widefield Array (MWA), the low-frequency Square Kilometre Array (SKA1 LOW) precursor located in Western Australia, the authors have completed the GaLactic and Extragalactic All-sky MWA (GLEAM) survey, and present the resulting extragalactic catalog, utilizing the first year of observations. The catalog covers 24,402 square degrees, over Declinations south of +30 degrees and Galactic latitudes outside 10 degrees of the Galactic Plane, excluding some areas such as the Magellanic Clouds. It contains 307,455 radio sources with 20 separate flux density measurements across 72 - 231 MHz, selected from a time- and frequency-integrated image centered at 200 MHz, with a resolution of ~ 2 arcminutes. Over the catalogued region, the authors estimate that the catalog is 90% complete at 170 mJy, and 50% complete at 55 mJy, and large areas are complete at even lower flux density levels. Its reliability is 99.97% above the 5-sigma detection threshold, which itself is typically 50 mJy. These observations constitute the widest fractional bandwidth and largest sky area survey at radio frequencies to date, and calibrate the low frequency flux density scale of the southern sky to better than 10%. The reference paper presents details of the flagging, imaging, mosaicking, and source extraction/characterization, as well as estimates of the completeness and reliability. All source measurements and images are available online at <a href="http://www.mwatelescope.org/">http://www.mwatelescope.org/</a>. This is the first in a series of publications describing the GLEAM survey results. GLEAM observes in week-long drift scan campaigns, with a single Dec strip observed each night. The observing bandwidth of 72-231 MHz is covered by shifting frequencies by 30.72 MHz every two minutes, avoiding the Orbcomm satellite constellation at 134-139 MHz. Thus, the frequencies of observation are 72-103, 103-134, 139-170, 170-200. and 200-231 MHz. These may be further subdivided for imaging purposes; in this study, the 30.72 MHz bandwidth is commonly subdivided into four 7.68 MHz sub-channels. The native channel resolution of these observations is 40 kHz and the native time resolution is 0.5 seconds. This paper concerns only data collected in the first year, i.e. four weeks between June 2013 and July 2014. The authors also do not image every observation, since the survey is redundant across approximately 50% of the observed RA ranges, and some parts are adversely acted by the Galactic plane and Centaurus A. Table 1 in the reference paper lists the observations which have been used to create this first GLEAM catalog. The HEASARC has converted the flux density units from those given in the original table (Jy and Jy/beam) to its standard units for radio flux densities (mJy and mJy/beam). This table was originally ingest by the HEASARC in February 2017 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/VIII/100">CDS Catalog VIII/100</a> file gleamegc.dat, the GLEAM Extragalactic Catalog. It was updated in May 2018 to the corrected version provided to the CDS by the author. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/MNRAS/447/3342
- Title:
- Galactic and LMC Cepheids Fourier parameters
- Short Name:
- J/MNRAS/447/3342
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a light-curve analysis of fundamental-mode Galactic and Large Magellanic Cloud (LMC) Cepheids based on the Fourier decomposition technique. We have compiled light-curve data for Galactic and LMC Cepheids in optical (VI), near-infrared (JHKs) and mid-infrared (3.6 and 4.5{mu}m) bands from the literature and determined the variation of their Fourier parameters as a function of period and wavelength. We observed a decrease in Fourier amplitude parameters and an increase in Fourier phase parameters with increasing wavelengths at a given period. We also found a decrease in the skewness and acuteness parameters as a function of wavelength at a fixed period. We applied a binning method to analyse the progression of the mean Fourier parameters with period and wavelength. We found that for periods longer than about 20d, the values of the Fourier amplitude parameters increase sharply for shorter wavelengths as compared to wavelengths longer than the J band. We observed the variation of the Hertzsprung progression with wavelength. The central period of the Hertzsprung progression was found to increase with wavelength in the case of the Fourier amplitude parameters and decrease with increasing wavelength in the case of phase parameters. We also observed a small variation of the central period of the progression between the Galaxy and LMC, presumably related to metallicity effects. These results will provide useful constraints for stellar pulsation codes that incorporate stellar atmosphere models to produce Cepheid light curves in various bands.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A70
- Title:
- Galactic and Magellanic Cloud Cepheids distance
- Short Name:
- J/A+A/550/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The metallicity dependence of the Cepheid period-luminosity (PL) relation is of importance in establishing the extragalactic distance scale. The aim of this paper is to investigate the metallicity dependence of the PL relation in V and K, based on a sample of 128 Galactic, 36 Large Magellanic Cloud (LMC), and 6 Small Magellanic Cloud (SMC) Cepheids with individual Baade-Wesselink (BW) distances (some of the stars also have an Hubble Space Telescope (HST) based and Hipparcos parallax or are in clusters) and individually determined metallicities from high-resolution spectroscopy. Literature values of the V-band, K-band, and radial velocity data were collected for the sample of Cepheids. Based on a (V-K) surface-brightness relation and a projection factor, distances were derived from a BW analysis. Since 2008, additional radial velocity data has been obtained using the 1.2m Euler telescope located at the La Silla observatory (see Groenewegen 2008A&A...488...25G for a description of the data taking and data reduction). The new Radial Velocity (RV) data are presented in Table 3.