- ID:
- ivo://CDS.VizieR/J/A+A/585/A141
- Title:
- Galactic center early-type stars catalog
- Short Name:
- J/A+A/585/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is still unclear whether the Sagittarius spiral arm is a major spiral arm in the Galaxy or whether it just outlines a region of enhanced star formation because of the local compression of gas. The best way to separate these scenarios out is to study the kinematics across the arm to determine the velocity perturbation it induces. A survey of early-type stars in the direction of the Galactic center is performed covering an area of 100 sq. deg with the aim of identifying candidates for a radial velocity study. Objective prism plates were obtained with the 4{deg} prism on the ESO Schmidt telescope using IIaO, 4415, and IIIaJ emulsions. The plates were digitized and more than 100k spectra were extracted down to a limiting magnitude of B=15m. The spectra were cross-correlated with a template with Balmer lines, which yielded a candidate list of 12675 early-type stars. Magnitudes and equivalent widths of strong lines were calculated from the spectra, which allowed us to estimate the individual extinctions and distances for 11075 stars.
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- ID:
- ivo://CDS.VizieR/J/A+A/584/A93
- Title:
- Galactic cold cores. V. Dust opacity
- Short Name:
- J/A+A/584/A93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The project Galactic Cold Cores has carried out Herschel photometric observations of interstellar clouds where Planck satellite survey has located cold and compact clumps. The sources represent different stages of cloud evolution from starless clumps to protostellar cores and are located in different Galactic environments. We examine this sample of 116 Herschel fields to estimate the submillimetre dust opacity and to look for variations that could be attributed to the evolutionary stage of the sources or to environmental factors, including the location within the Galaxy. The submillimetre dust opacity is derived from Herschel data and near-infrared observations of the reddening of background stars are converted to near-infrared optical depth. We investigate the systematic errors affecting these parameters and use modelling to make corrections for the expected biases. The ratio of 250{mu}m and J band opacities is correlated with the Galactic location and the star formation activity. Local variations in the ratio {tau}(250{mu}m)/{tau}(J) are searched using the correlation plots and maps of the opacity ratio. We find a median ratio of {tau}(250{mu}m)/{mu}(J)=(1.6+/-0.2)*10^-3^, which is more than three times the mean value reported for the diffuse medium. Assuming an opacity spectral index {beta}=1.8 instead of {beta}=2.0, the value would be smaller by ~30%. No significant systematic variation is detected with Galactocentric distance or with Galactic height. Examination of the {tau}(250{mu}m)/{tau}(J) maps reveals half a dozen fields with clear indications of local increase of submillimetre opacity, up to {tau}(250{mu}m)/{tau}(J)~4*10^-3^, towards the densest clumps. These are all nearby fields with spatially resolved clumps of high column density. We interpret the increase in the far-infrared opacity as a sign of grain growth in the densest and coldest regions of interstellar clouds.
- ID:
- ivo://CDS.VizieR/J/MNRAS/503/5351
- Title:
- Galactic extinction at low Galactic latitudes
- Short Name:
- J/MNRAS/503/5351
- Date:
- 19 Jan 2022 00:31:53
- Publisher:
- CDS
- Description:
- We use near-infrared (J-K) colours of bright 2MASS galaxies, measured within a 7-arcsec-radius aperture, to calibrate the Schlegel, Finkbeiner & Davis DIRBE/IRAS Galactic extinction map at low Galactic latitudes (|b|<10{deg}). Using 3460 galaxies covering a large range in extinction (up to A_K_=1.15mag or E(B-V)~=3.19mag), we derive a correction factor f=0.83+/-0.01 by fitting a linear regression to the colour-extinction relation, confirming that the Schlegel et al. maps overestimate the extinction. We argue that the use of only a small range in extinction (e.g., A_K_<0.4mag) increases the uncertainty in the correction factor and may overestimate it. Our data confirm the Fitzpatrick extinction law for the J- and K-band. We also tested four all-sky extinction maps based on Planck satellite data. All maps require a correction factor as well. In three cases, the application of the respective extinction correction to the galaxy colours results in a reduced scatter in the colour-extinction relation, indicating a more reliable extinction correction. Finally, the large galaxy sample allows an analysis of the calibration of the extinction maps as a function of Galactic longitude and latitude. For all but one extinction map, we find a marked offset between the Galactic Centre and Anticentre region, but not with the dipole of the cosmic microwave background. Based on our analysis, we recommend the use of the GNILC extinction map by Planck Collaboration XLVIII with a correction factor f=0.86+/-0.01.
- ID:
- ivo://CDS.VizieR/J/A+A/561/A142
- Title:
- Galactic extinction from SDSS BHB stars
- Short Name:
- J/A+A/561/A142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use 12530 photometrically-selected BHB stars from Sloan Digital Sky Survey DR7 to estimate, the total extinction of the Milky Way in high Galactic latitude, RV and AV in each line of sight. A Bayesian method is developed to estimate the reddening values in the given lines of sight. Based on the most likely values of reddening in multiple colors, we are able to derive the values of RV and AV. We select 94 zero-reddened BHB stars from 7 globular cluster as the template. The reddening in the 4 SDSS colors for the northern Galactic cap are estimated by comparing the field BHB stars with the template stars.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A135
- Title:
- Galactic interstellar dust Gaia-2MASS 3D maps
- Short Name:
- J/A+A/625/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gaia stellar measurements are currently revolutionizing our knowledge of the evolutionary history of the Milky Way. 3D maps of the interstellar dust provide complementary information and are a tool for a wide range of uses. We built 3D maps of the dust in the Local arm and surrounding regions. To do so, Gaia DR2 photometric data were combined with 2MASS measurements to derive extinction toward stars that possess accurate photometry and relative uncertainties on DR2 parallaxes smaller than 20%. We applied a new hierarchical inversion algorithm to the individual extinctions that is adapted to large datasets and to an inhomogeneous target distribution. Each step associates regularized Bayesian inversions in all radial directions and a subsequent inversion in 3D of all their results. Each inverted distribution serves as a prior for the subsequent step, and the spatial resolution is progressively increased. We present the resulting 3D distribution of the dust in a 6x6x0.8kpc^3^ volume around the Sun. Its main features are found to be elongated along different directions that vary from below to above the mid-plane. The outer part of Carina-Sagittarius, mainly located above the mid-plane, the Local arm/Cygnus Rift around and above the mid-plane, and the fragmented Perseus arm are oriented close to the direction of circular motion. The spur of more than 2kpc length (nicknamed the split) that extends between the Local Arm and Carina-Sagittarius, the compact near side of Carina-Sagittarius, and the Cygnus Rift below the Plane are oriented along l~40 to 55{deg}. Dust density images in vertical planes reveal a wavy pattern in some regions and show that the solar neighborhood within 500 pc remains atypical by its extent above and below the Plane. We show several comparisons with the locations of molecular clouds, HII regions, O stars, and masers. The link between the dust concentration and these tracers is markedly different from one region to the other
- ID:
- ivo://CDS.VizieR/J/A+A/653/A133
- Title:
- GALACTICNUCLEUS IV. JHKs imaging survey
- Short Name:
- J/A+A/653/A133
- Date:
- 10 Mar 2022 11:26:04
- Publisher:
- CDS
- Description:
- The extreme extinction (A_V_~30mag) and its variation on arc-second scales towards the Galactic centre hamper the study of its stars. Their analysis is restricted to the near infrared (NIR) regime, where the extinction curve can be approximated by a broken power law for the JHKs bands. Therefore, correcting for extinction at these wavelengths is fundamental to analyse the structure and stellar population of the central regions of our Galaxy. We aim at: (1) Discussing different strategies to de-redden the photometry and checking the usefulness of extinction maps to deal with variable stars. (2) Building and making publicly available extinction maps for the NIR bands JHKs. (3) Creating a de-reddened catalogue of the GALACTICNUCLEUS (GNS) survey, identifying foreground stars. (4) Performing a preliminary analysis of the de-reddened $K_s$ luminosity functions (KLFs). We use photometry from the GNS survey to create extinction maps for the whole catalogue. We take red clump (RC) and red giant stars of similar brightness as a reference to build the maps, and de-redden the GNS photometry. We discuss the limitations of the process and analyse non-linear effects of the de-reddening. We create high resolution (~3'') extinction maps with low statistical and systematics uncertainties (<~5%), and compute average extinctions for each of the regions covered by the GNS. We check that our maps effectively correct the differential extinction reducing the spread of the RC features by a factor of ~2. We assess the validity of the broken power law approach computing two equivalent extinction maps A_H_ using either JH and HKs photometry for the same reference stars, and obtain compatible average extinctions within the uncertainties. Finally, we analyse de-reddened KLFs for different line-of-sights and find that the regions belonging to the NSD contain a homogeneous stellar population that is significantly different from the one in the innermost bulge regions.
- ID:
- ivo://CDS.VizieR/J/A+A/610/A83
- Title:
- GALACTICNUCLEUS: JHKs imaging survey
- Short Name:
- J/A+A/610/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic Centre is of fundamental astrophysical interest, but existing near-infrared surveys fall short covering it adequately, either in terms of angular resolution, multi-wavelength coverage, or both. Here we introduce the GALACTICNUCLEUS survey, a JHKs imaging survey of the centre of the Milky Way with a 0.2" angular resolution. The purpose of this paper is to present the observations of Field 1 of our survey, centred approximately on SgrA* with an approximate size of 7.95'x3.43'. We describe the observational set-up and data reduction pipeline and discuss the quality of the data. Finally, we present the analysis of the data. The data were acquired with the near-infrared camera HAWK-I (High Acuity Wide field K-band Imager) at the ESO VLT (Very Large Telescope). Short readout times in combination with the speckle holography algorithm allowed us to produce final images with a stable, Gaussian PSF (point spread function) of 0.2" FWHM (full width at half maximum). Astrometric calibration is achieved via the VVV (VISTA Variables in the Via Lactea) survey and photometric calibration is based on the SIRIUS/IRSF (Infrared Survey Facility telescope) survey. The quality of the data is assessed by comparison between observations of the same field with different detectors of HAWK-I and at different times. We reach 5{sigma} uncertainties are less than 0.05" at J<=20, H<=17, and Ks<=16. We can distinguish five stellar populations in the colour-magnitude diagrams; three of them appear to belong to foreground spiral arms, and the other two correspond to high- and low-extinction star groups at the Galactic Centre. We use our data to analyse the near-infrared extinction curve and find some evidence for a possible difference between the extinction index between J-H and H-Ks. However, we conclude that it can be described very well by a power law with an index of JHKs=2.30+.-0.08. We do not find any evidence that this index depends on the position along the line of sight, or on the absolute value of the extinction. We produce extinction maps that show the clumpiness of the ISM (interstellar medium) at the Galactic Centre. Finally, we estimate that the majority of the stars have solar or super-solar metallicity by comparing our extinction-corrected colour-magnitude diagrams with isochrones with different metallicities and a synthetic stellar model with a constant star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A20
- Title:
- GALACTICNUCLEUS JHKs imaging survey. II.
- Short Name:
- J/A+A/631/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The high extinction and extreme source crowding of the central regions of the Milky Way are serious obstacles to the study of the structure and stellar population of the Galactic centre (GC). Surveys that cover the GC region (2MASS, UKIDSS, VVV, SIRIUS) do not have the necessary high angular resolution. Therefore, a high angular resolution survey in the near infrared is crucial to improve the state of the art. Here, we present the GALACTICNUCLEUS catalogue, a near infrared JHKs high angular resolution (0.2") survey of the nuclear bulge of the Milky Way. We explain in detail the data reduction, data analysis, calibration, and uncertainty estimation of the GALACTICNUCLEUS survey. We assess the data quality comparing our results with previous surveys. We obtained accurate JHKs photometry ~3.3x10^6^ stars in the GC detecting around 20% in J, 65% in H and 90% in Ks. The survey covers a total area of ~0.3 square degrees, which corresponds to ~6000pc^2^. The GALACTICNUCLEUS survey reaches 5 sigma detections for J~22mag, H~21mag and Ks~21mag. The uncertainties are below 0.05mag at J~21mag, H~19mag and Ks~18mag. The zero point systematic uncertainty is <~0.04mag in all three bands. We present colour-magnitude diagrams for the different regions covered by the survey.
- ID:
- ivo://CDS.VizieR/J/MNRAS/396/553
- Title:
- Galactic RR Lyrae data
- Short Name:
- J/MNRAS/396/553
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use accurate absolute proper motions and Two-Micron All-Sky Survey Ks -band apparent magnitudes for 364 Galactic RR Lyrae variables to determine the kinematical parameters of the Galactic RR Lyrae population and constrain the zero-point of the Ks-band period-luminosity relation for these stars via statistical parallax.
- ID:
- ivo://CDS.VizieR/J/ApJ/723/1019
- Title:
- Galactic SFR and gas surface densities
- Short Name:
- J/ApJ/723/1019
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the relation between star formation rate (SFR) and gas surface densities in Galactic star-forming regions using a sample of young stellar objects (YSOs) and massive dense clumps. Our YSO sample consists of objects located in 20 large molecular clouds from the Spitzer cores to disks (c2d; Evans, 2009, Cat. J/ApJS/181/321) and Gould's Belt (GB) survey (L. Allen et al. 2010, in preparation). These data allow us to probe the regime of low-mass star formation, essentially invisible to tracers of high-mass star formation used to establish extragalactic SFR-gas relations. We estimate the gas surface density ({Sigma}_gas_) from extinction (A_V_) maps and YSO SFR surface densities ({Sigma}_SFR_) from the number of YSOs, assuming a mean mass and lifetime. We also divide the clouds into evenly spaced contour levels of A_V_, counting only Class I and Flat spectral energy distribution YSOs, which have not yet migrated from their birthplace. For a sample of massive star-forming clumps, we derive SFRs from the total infrared luminosity and use HCN gas maps to estimate gas surface densities. We find that c2d and GB clouds lie above the extragalactic SFR-gas relations (e.g., Kennicutt-Schmidt law) by factors of up to 17. We use ^12^CO and ^13^CO gas maps of the Perseus and Ophiuchus clouds from the COMPLETE survey (Ridge et al. 2006AJ....131.2921R) to estimate gas surface densities and compare to measurements from A_V_ maps.
