- ID:
- ivo://CDS.VizieR/J/A+A/644/A140
- Title:
- VVVEXMAP-BULGE High resolution reddening map
- Short Name:
- J/A+A/644/A140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A detailed study of the Galactic bulge stellar population necessarily requires an accurate representation of the interstellar extinction, particularly toward the Galactic plane and center, where severe and differential reddening is expected to vary on sub-arcmin scales. Although recent infrared surveys have addressed this problem by providing extinction maps across the whole Galactic bulge area, dereddened color-magnitude diagrams near the plane and center appear systematically undercorrected, prompting the need for higher resolution. These undercorrections affect any stellar study sensitive to color (e.g., star formation history analyses via color-magnitude diagram fitting), either making them inaccurate or limiting them to small and relatively stable extinction windows where this value is low and better constrained. This study is aimed at providing a high-resolution (2-arcmin to 10-arcsec) color excess map for the VVV bulge area in J-Ks color. We used the MW-BULGE-PSFPHOT catalogs, sampling 300deg^2^ across the Galactic bulge (|l|<10{deg} and -10{deg}<b<5{deg}) to isolate a sample of red clump and red giant branch stars, for which we calculated the average J-Ks color in a fine spatial grid in (l, b) space. We obtained an E(J-Ks) map spanning the VVV bulge area of roughly 300deg^2^, with the equivalent of a resolution between 1-arcmin for bulge outskirts (l<-6{deg}) to below 20-arcsec within the central |l|<1{deg}, and below 10-arcsec for the innermost area (|l|<1{deg} and |b|<3{deg}). The results are publicly available at http://basti-iac.oa-teramo.inaf.it/vvvexmap/
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/893/65
- Title:
- VVV Survey microlensing events in the Gal. Bulge
- Short Name:
- J/ApJ/893/65
- Date:
- 19 Jan 2022 11:43:07
- Publisher:
- CDS
- Description:
- We search for microlensing events in the zero-latitude area of the Galactic Bulge using the VVV Survey near-IR data. We have discovered a total sample of N=630 events within an area covering 20.68deg^2^ between the years 2010 and 2015. In this paper, we describe the search and present the data for the final sample, including near-IR magnitudes, colors, and proper motions, as well as the standard microlensing parameters. We use the near-IR color-magnitude and color-color diagrams to select NRC=290 events with red-clump sources to analyze the extinction properties of the sample in the central region of the Galactic plane. The timescale distribution and its dependence in the longitude axis is presented. The mean timescale decreases as we approach the Galactic minor axis (b=0{deg}). Finally, we give examples of special microlensing events, such as binaries, short-timescale events, and events with a strong parallax effect.
- ID:
- ivo://CDS.VizieR/J/A+A/591/A145
- Title:
- VVV Survey outer bulge RRab stars
- Short Name:
- J/A+A/591/A145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VISTA Variables in the Via Lactea (VVV) is a near-IR time-domain survey of the Galactic bulge and southern plane. One of the main goals of this survey is to reveal the 3D structure of the Milky Way through their variable stars. In particular, enormous numbers of RR Lyrae stars have been discovered in the inner regions of the bulge (-8{deg}<~b<~-1{deg}) by optical surveys such as OGLE and MACHO, but leaving an unexplored window of more than ~47 sq deg (-10.0{deg}<~l<~+10.7{deg} and -10.3{deg}<~b<~-8.0{deg}) observed by the VVV Survey. Our goal is to characterize the RR Lyrae stars in the outer bulge in terms of their periods, amplitudes, Fourier coefficients, and distances in order to evaluate the 3D structure of the bulge in this area. The distance distribution of RR Lyrae stars will be compared to that of red clump stars, which is known to trace a X-shaped structure, in order to determine whether these two different stellar populations share the same Galactic distribution. A search for RR Lyrae stars was performed in more than ~47 sq deg at low Galactic latitudes (-10.3{deg}<~b<~-8.0{deg}). In the procedure the {chi}^2^ value and analysis of variance (AoV) statistic methods were used to determine the variability and periodic features of the light curves, respectively. To prevent misclassifications, the analysis was performed only on the fundamental mode RR Lyrae stars (RRab) owing to similarities found in the near-IR light curve shapes of contact eclipsing binaries (W UMa) and first overtone RR Lyrae stars (RRc). On the other hand, the red clump stars of the same analyzed tiles were selected, and cuts in the color-magnitude diagram were applied and the maximum distance restricted to ~20kpc in order to construct a similar catalog in terms of distances and covered area compared to the RR Lyrae stars. We report the detection of more than 1000 RR Lyrae ab-type stars in the VVV Survey located in the outskirts of the Galactic bulge. A few of them are possibly associated with the Sagittarius Dwarf Spheroidal Galaxy. We calculated colours, reddening, extinction, and distances of the detected RR Lyrae stars in order to determine the outer bulge 3D structure. Our main result is that, at the low galactic latitudes mapped here, the RR Lyrae stars trace a centrally concentrated spheroidal distribution. This is a noticeably different spatial distribution to the one traced by red clump stars known to follow a bar and X-shaped structure. We estimate the completeness of our sample at 80% for K_s_<=15mag.
- ID:
- ivo://CDS.VizieR/J/AJ/153/179
- Title:
- VVV Survey RR Lyr stars in Southern Galactic plane
- Short Name:
- J/AJ/153/179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deep near-IR images from the VISTA Variables in the Via Lactea (VVV) Survey were used to search for RR Lyrae stars in the Southern Galactic plane. A sizable sample of 404 RR Lyrae of type ab stars was identified across a thin slice of the fourth Galactic quadrant (295{deg}<l<350{deg}, -2.24{deg}<b<-1.05{deg}). The sample's distance distribution exhibits a maximum density that occurs at the bulge tangent point, which implies that this primarily Oosterhoff type I population of RRab stars does not trace the bar delineated by their red clump counterparts. The bulge RR Lyrae population does not extend beyond l~340{deg}, and the sample's spatial distribution presents evidence of density enhancements and substructure that warrants further investigation. Indeed, the sample may be employed to evaluate Galactic evolution models, and is particularly lucrative since half of the discovered RR Lyrae are within reach of Gaia astrometric observations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/1685
- Title:
- Weak Galactic radio sources spectral indices
- Short Name:
- J/MNRAS/473/1685
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the next few years the classification of radio sources observed by the large surveys will be a challenging problem and spectral index is a powerful tool for addressing it. Here we present an algorithm to estimate the spectral index of sources from multiwavelength radio images. We have applied our algorithm to SCORPIO, a Galactic plane survey centred around 2.1GHz carried out with Australian Telescope Compact Array and found we can measure reliable spectral indices only for sources stronger than 40 times the rms noise. Above a threshold of 1mJy, the source density in SCORPIO is 20 per cent greater than in a typical extragalactic field, like Australia Telescope Large Area Survey because of the presence of Galactic sources. Among this excess population, 16 sources per square degree have a spectral index of about zero suggesting optically thin thermal emission such as HII regions and planetary nebulae, while 12 per square degree present a rising spectrum, suggesting optically thick thermal emission such as stars and UCHII regions.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A145
- Title:
- What is the Milky Way outer halo made of?
- Short Name:
- J/A+A/608/A145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a framework where galaxies form hierarchically, extended stellar haloes are predicted to be an ubiquitous feature around Milky Way-like galaxies and to consist mainly of the shredded stellar component of smaller galactic systems. The type of accreted stellar systems are expected to vary according to the specific accretion and merging history of a given galaxy, and so is the fraction of stars formed in-situ versus accreted. Analysis of the chemical properties of Milky Way halo stars out to large Galactocentric radii can provide important insights into the properties of the environment in which the stars that contributed to the build-up of different regions of the Milky Way stellar halo formed. In this work we focus on the outer regions of the Milky Way stellar halo, by determining chemical abundances of halo stars with large present-day Galactocentric distances, >15 kpc. The data-set we acquired consists of high resolution HET/HRS, Magellan/MIKE and VLT/UVES spectra for 28 red giant branch stars covering a wide metallicity range, -3.1<[Fe/H]<-0.6. We show that the ratio of alpha-elements over Fe as a function of [Fe/H] for our sample of outer halo stars is not dissimilar from the pattern shown by MW halo stars from solar neighborhood samples. On the other hand, significant differences appear at [Fe/H]>-1.5 when considering chemical abundance ratios such as [Ba/Fe], [Na/Fe], [Ni/Fe], [Eu/Fe], [Ba/Y]. Qualitatively, this type of chemical abundance trends are observed in massive dwarf galaxies, such as Sagittarius and the Large Magellanic Cloud. This appears to suggest a larger contribution in the outer halo of stars formed in an environment with high initial star formation rate and already polluted by asymptotic giant branch stars with respect to inner halo samples.
- ID:
- ivo://CDS.VizieR/J/AJ/155/50
- Title:
- WISE photometry of Be stars in young open clusters
- Short Name:
- J/AJ/155/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Through the modeling of near-infrared photometry of star-plus disk systems with the codes BEDISK/BERAY, we successfully describe the Wide-Field Infrared Survey Explorer (WISE) photometric characteristics of Be stars in five young open clusters, NGC 663, NGC 869, NGC 884, NGC 3766, and NGC 4755, broadly studied in the literature. WISE photometry allows previously known Be stars to be detected and to find new Be candidates which could be confirmed spectroscopically. The location of Be stars in the WISE color-magnitude diagram, separates them in two groups; active (Be stars hosting a developed circumstellar disk) and quiescent objects (Be stars in a diskless phase), and this way, we can explore how often stars are observed in these different stages. The variability observed in most active variable Be stars is compatible with a disk dissipation phase. We find that 50% of Be stars in the studied open clusters are in an active phase. We can interpret this as Be stars having a developed circumstellar disk one-half of the time. The location of Be stars with a developed disk in the color-magnitude diagram require mass loss rates in agreement with values recently reported in the literature. For these objects, we expect to have a tight relation between the equivalent width of the H{alpha} line and the mass of the disk, if the inclination is known. Also, near-infrared photometry of Be stars in stellar clusters has the potential of being useful to test whether there is a preferential viewing angle.
- ID:
- ivo://CDS.VizieR/J/AJ/154/163
- Title:
- WISE-selected candidate SFRs beyond the Outer Arm
- Short Name:
- J/AJ/154/163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The outer Galaxy beyond the Outer Arm provides a good opportunity to study star formation in an environment significantly different from that in the solar neighborhood. However, star-forming regions in the outer Galaxy have never been comprehensively studied or cataloged because of the difficulties in detecting them at such large distances. We studied 33 known young star-forming regions associated with 13 molecular clouds at R_G_>=13.5 kpc in the outer Galaxy with data from the Wide-field Infrared Survey Explorer (WISE) mid-infrared all-sky survey (Wright et al. 2010AJ....140.1868W; Jarrett et al. 2011ApJ...735..112J). From their color distribution, we developed a simple identification criterion of star-forming regions in the outer Galaxy with the WISE color. We applied the criterion to all the WISE sources in the molecular clouds in the outer Galaxy at R_G_>=13.5 kpc detected with the Five College Radio Astronomy Observatory (FCRAO) ^12^CO survey of the outer Galaxy (Heyer et al. 1998ApJS..115..241H), of which the survey region is 102.49{deg}=<l=<141.54{deg}, -3.03{deg}=<b=<5.41{deg}, and successfully identified 711 new candidate star-forming regions in 240 molecular clouds. The large number of samples enables us to perform the statistical study of star formation properties in the outer Galaxy for the first time. This study is crucial to investigate the fundamental star formation properties, including star formation rate, star formation efficiency, and initial mass function, in a primordial environment such as the early phase of the Galaxy formation.
- ID:
- ivo://CDS.VizieR/J/AJ/153/128
- Title:
- WOCS. LXXV. Hyades&Praesepe stellar lithium data
- Short Name:
- J/AJ/153/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- WIYN/Hydra spectroscopy (at R~15000) of the moderately metal-rich Praesepe and Hyades open clusters was used to study their main-sequence (MS) iron ([Fe/H]) and lithium (A(Li)) abundances. Self-consistent [Fe/H] and Li analyses of these clusters of consistent age, which we re-evaluate, confirms that they have consistent [Fe/H] and provides a foundation to investigate the poorly understood G-dwarf and F-dwarf Li-depletions. Neither phenomenon agrees with standard stellar evolution theory, but possible explanations abound. We supplement our A(Li) with previously published results placed on a uniform abundance scale. This creates the largest self-consistently analyzed sample of A(Li) in both the Hyades (90) and Praesepe (110). For each star, high-precision UBVRI photometry was used to determine a 10-color-based T_eff_ and then to test for photometric peculiarities indicated by a large {sigma}_Teff_ (>75 K). The stars that have large {sigma}_Teff_ were predominantly found to be binaries or stars with peculiar (apparent) A(Li). When considering only proper-motion members that have low {sigma}_Teff_ and are also photometrically consistent with the cluster MS fiducial, each cluster has a more tightly defined Li morphology than previously observed and the two clusters' A(Li) are indistinguishable. This suggests that clusters of consistent age and metallicity may have consistent Li-depletion trends across a broad range of T_eff_; no additional major parameters are required, at least for these two clusters. We propose that the combined Hyades and Praesepe data offer more rigorous constraints than does either cluster alone, and we discuss newly revealed features of the combined Li-T_eff_ trend.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/1525
- Title:
- XMM-Newton and Chandra monitoring of Sgr A*
- Short Name:
- J/MNRAS/454/1525
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the X-ray flaring activity of Sgr A* during all the 150 XMM-Newton and Chandra observations pointed at the Milky Way centre over the last 15 years. This includes the latest XMM-Newton and Chandra campaigns devoted to monitoring the closest approach of the very red Br{gamma} emitting object called G2. The entire data set analysed extends from 1999 September through 2014 November. We employed a Bayesian block analysis to investigate any possible variations in the characteristics (frequency, energetics, peak intensity, duration) of the flaring events that Sgr A* has exhibited since their discovery in 2001. We observe that the total bright or very bright flare luminosity of Sgr A* increased between 2013 and 2014 by a factor of 2-3 (~3.5{sigma} significance). We also observe an increase (~99.9 percent significance) from 0.27+/-0.04 to 2.5+/-1.0/d of the bright or very bright flaring rate of Sgr A*, starting in late summer 2014, which happens to be about six months after G2's pericentre passage. This might indicate that clustering is a general property of bright flares and that it is associated with a stationary noise process producing flares not uniformly distributed in time (similar to what is observed in other quiescent black holes). If so, the variation in flaring properties would be revealed only now because of the increased monitoring frequency. Alternatively, this may be the first sign of an excess accretion activity induced by the close passage of G2. More observations are necessary to distinguish between these two hypotheses.
