- ID:
- ivo://CDS.VizieR/J/ApJS/206/13
- Title:
- Blazars with {gamma}-ray counterparts. II.
- Short Name:
- J/ApJS/206/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A significant fraction (~30%) of the high-energy gamma-ray sources listed in the second Fermi Large Area Telescope catalog (2FGL) are still of unknown origin, being not yet associated with counterparts at low energies. We recently developed a new association method to identify if there is a {gamma}-ray blazar candidate within the positional uncertainty region of a generic 2FGL source. This method is entirely based on the discovery that blazars have distinct infrared colors with respect to other extragalactic sources found, thanks to the Wide-field Infrared Survey Explorer (WISE) all-sky observations. Several improvements have also been performed to increase the efficiency of our method in recognizing {gamma}-ray blazar candidates. In this paper we applied our method to two different samples, the first constituted by unidentified {gamma}-ray sources (UGSs), and the second by active galaxies of uncertain type, both listed in the 2FGL. We present a catalog of IR counterparts for ~20% of the UGSs investigated. Then, we also compare our results for the associated sources with those present in the literature. In addition, we illustrate the extensive archival research carried out to identify the radio, infrared, optical, and X-ray counterparts of the WISE-selected, {gamma}-ray blazar candidates. Finally, we discuss the future developments of our method based on ground-based follow-up observations.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/207/16
- Title:
- BL Lac candidates for TeV observations
- Short Name:
- J/ApJS/207/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BL Lac objects are the most numerous class of extragalactic TeV-detected sources. One of the biggest difficulties in investigating their TeV emission is due to their limited number, since only 47 BL Lac objects are known to be TeV emitters. In this paper, we propose new criteria to select TeV BL Lac candidates based on infrared and X-ray observations. We apply our selection criteria to the BL Lac objects listed in the ROMA-BZCAT catalog (Cat. J/A+A/495/691), thereby identifying 41 potential TeV emitters. We then perform a search over a more extended sample combining the ROSAT bright source catalog (Cat. IX/10) and the WISE all-sky survey (Cat. II/311), revealing 54 additional candidates for TeV observations. Our investigation also led to a tentative classification of 16 unidentified X-ray sources as BL Lac candidates. This analysis provides new interesting BL Lac targets for future observations with ground-based Cherenkov telescopes.
- ID:
- ivo://CDS.VizieR/J/A+A/538/A26
- Title:
- BL Lac objects beyond z=1.3
- Short Name:
- J/A+A/538/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of the {gamma}-ray sky with Fermi led to significant advances towards understanding blazars, the most extreme class of active galactic nuclei. A large fraction of the population detected by Fermi is formed by BL Lacertae (BL Lac) objects, whose sample has always suffered from a severe redshift incompleteness due to the quasi-featureless optical spectra. Our goal is to provide a significant increase of the number of confirmed high-redshift BL Lac objects contained in the 2 LAC Fermi/LAT catalog.
- ID:
- ivo://CDS.VizieR/J/A+A/521/A18
- Title:
- Blue stars with disk photometry in NGC 6611
- Short Name:
- J/A+A/521/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6611 and its parental cloud, the Eagle Nebula (M 16), are well-studied star-forming regions, thanks to their large content of both OB stars and stars with disks and the observed ongoing star formation. In our previous studies of the Eagle Nebula, we identified 834 disk-bearing stars associated with the cloud, after detecting their excesses in NIR bands from J band to 8.0um. In this paper, we study in detail the nature of a subsample of disk-bearing stars that show peculiar characteristics. They appear older than the other members in the V vs. V-I diagram, and/or they have one or more IRAC colors at pure photospheric values, despite showing NIR excesses, when optical and infrared colors are compared.
- ID:
- ivo://CDS.VizieR/J/A+A/463/789
- Title:
- Blue stragglers in open clusters
- Short Name:
- J/A+A/463/789
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of blue-straggler candidates in galactic open clusters. It is based on the inspection of the colour-magnitude diagrams of the clusters, and it updates and supersedes the first version (Ahumada & Lapasset, 1995, Cat. <J/A+AS/109/375>). A new bibliographical search was made for each cluster, and the resulting information is organised into two tables. Some methodological aspects have been revised, in particular those concerning the delimitation of the area in the diagrams where the stragglers are selected. A total of 1887 blue-straggler candidates have been found in 427 open clusters of all ages, doubling the original number. The catalogued stars are classified into two categories mainly according to membership information.
- ID:
- ivo://CDS.VizieR/J/AJ/152/16
- Title:
- Bolometric flux estimation for cool evolved stars
- Short Name:
- J/AJ/152/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Estimation of bolometric fluxes (F_BOL_) is an essential component of stellar effective temperature determination with optical and near-infrared interferometry. Reliable estimation of F_BOL_ simply from broadband K-band photometry data is a useful tool in those cases were contemporaneous and/or wide-range photometry is unavailable for a detailed spectral energy distribution (SED) fit, as was demonstrated in Dyck et al. Recalibrating the intrinsic F_BOL_ versus observed F_2.2{mu}m_ relationship of that study with modern SED fitting routines, which incorporate the significantly non-blackbody, empirical spectral templates of the INGS spectral library (an update of the library in Pickles) and estimation of reddening, serves to greatly improve the accuracy and observational utility of this relationship. We find that F_BOL_ values predicted are roughly 11% less than the corresponding values predicted in Dyck et al., indicating the effects of SED absorption features across bolometric flux curves.
- ID:
- ivo://CDS.VizieR/J/MNRAS/471/629
- Title:
- Bootes-HiZELS. Em-line galaxies at z=0.4-4.7
- Short Name:
- J/MNRAS/471/629
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of ~1000 emission-line galaxies at z=0.4-4.7 from the ~0.7deg^2^ High-z Emission-Line Survey in the Bootes field identified with a suite of six narrow-band filters at ~=0.4-2.1{mu}m. These galaxies have been selected on their Ly{alpha} (73), [OII] (285), H{beta}/[OIII] (387) or H{alpha} (362) emission line, and have been classified with optical to near-infrared colours. A subsample of 98 sources have reliable redshifts from multiple narrow-band (e.g. [OII]-H{alpha}) detections and/or spectroscopy. In this survey paper, we present the observations, selection and catalogues of emitters. We measure number densities of Ly{alpha}, [OII], H{beta}/[OIII] and H{alpha} and confirm strong luminosity evolution in star-forming galaxies from z~0.4 to ~5, in agreement with previous results. To demonstrate the usefulness of dual-line emitters, we use the sample of dual [OII]-H{alpha} emitters to measure the observed [OII]/H{alpha} ratio at z=1.47. The observed [OII]/H{alpha} ratio increases significantly from 0.40+/-0.01 at z=0.1 to 0.52+/-0.05 at z=1.47, which we attribute to either decreasing dust attenuation with redshift, or due to a bias in the (typically) fibre measurements in the local Universe that only measure the central kpc regions. At the bright end, we find that both the H{alpha} and Ly{alpha} number densities at z~=2.2 deviate significantly from a Schechter form, following a power law. We show that this is driven entirely by an increasing X-ray/active galactic nucleus fraction with line luminosity, which reaches ~=100 per cent at line luminosities L>=3x10^44^erg/s.
- ID:
- ivo://CDS.VizieR/J/ApJ/853/47
- Title:
- Brightest cluster galaxies bright in 22um (W4BCGs)
- Short Name:
- J/ApJ/853/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Brightest cluster galaxies (BCGs) are believed to have assembled most of their stars early in time and therefore should be passively evolving at low redshifts and appear "red-and-dead." However, there have been reports that a minority of low-redshift BCGs still have ongoing star formation rates (SFRs) of a few to even ~100M_{sun}_/yr. Such BCGs are found in "cool-core" ("CC") clusters, and their star formation is thought to be fueled by "cooling flow." To further investigate the implications of low-redshift, star-forming BCGs, we perform a systematic search using the 22{mu}m data ("W4" band) from the Wide-field Infrared Survey Explorer (WISE) on the GMBCG catalog, which contains 55424 BCGs at 0.1<~z<~0.55 identified in the Sloan Digital Sky Survey (SDSS). Our sample consists of 389 BCGs that are bright in W4 ("W4BCGs"), most being brighter than 5mJy. While some (<~20%) might host active galactic nuclei, most W4BCGs should owe their strong mid-IR emissions to dust-enshrouded star formation. Their median total IR luminosity (L_IR_) is 5x10^11^L_{sun}_ (SFR~50M_{sun}_/yr), and 27% of the whole sample has L_IR_>10^12^L_{sun}_ (SFR>100M_{sun}_/yr). Using 10 W4BCGs that have Chandra X-ray data, we show that 7 of them are possibly in CC clusters. However, in most cases (five out of seven) the mass deposition rate cannot account for the observed SFR. This casts doubt on the idea that cooling flows are the cause of the star formation in non-quiescent BCGs.
- ID:
- ivo://CDS.VizieR/J/A+A/466/917
- Title:
- Brightest stars of sigma Orionis cluster
- Short Name:
- J/A+A/466/917
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The very young sigma Orionis cluster (about 3Ma) is a cornerstone for the understanding of the formation of stars and substellar objects down to planetary masses. However, its stellar population is far to be completely known. This study has the purpose of identifying and characterising the most massive stars of sigma Orionis to complement current and future deep searches for brown dwarfs and planetary-mass objects in the cluster. I have cross-correlated the sources in the Tycho and 2MASS catalogues in a region of 30arcmin radius with centre in the O-type star sigma Ori A. In the area, I have studied the membership in the Ori OB 1b Association of the brightest stars in the optical using astrometric, X-ray and infrared and optical photometric data from public catalogues and spectroscopic data from the literature. A list of 26 young stars, four candidate young stars and 16 probable foreground stars has arised from the study. Seven young stars probably harbour discs (four are new). There is no mass-dependence of the disc frequency in the cluster. I have derived for the first time the mass spectrum in sigma Orionis from 1.1 to 24M_{sun}_ (alpha=+2.0^+0.2^_-0.1_; roughly Salpeter-like). I have also provided additional proofs on the existence of several spatially superimposed stellar populations in the direction of sigma Orionis. Finally, the cluster may be closer and older than previously considered.
- ID:
- ivo://CDS.VizieR/J/ApJ/902/127
- Title:
- Bright Gaia white dwarfs with unWISE photometry
- Short Name:
- J/ApJ/902/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studies of excess infrared radiation around white dwarfs provide important constraints on the evolution of planetary systems and low-mass companions beyond the main-sequence stage. In this paper series, we focus on identifying and characterizing bright white dwarfs with an infrared excess. Here, we present 188 infrared excess candidates from Gaia and unWISE, 147 of which are new discoveries. Further characterization of this sample can significantly increase the current list of white dwarf debris disks and white dwarfs with low-mass companions.
