Abstract This study employs stellar parameters from spectroscopic surveys and Zhang et al. (2023) based on Gaia BP/RP (XP) spectra, along with photometric data from Galaxy Evolution Explorer (GALEX), UV/Optical Telescope (UVOT), and Gaia, to obtain extensive ultraviolet color excess information for the relevant bands of GALEX and UVOT. By considering the impact of stellar parameters (T eff, [Fe/H], and log g ) on intrinsic color indices and utilizing the blue-edge method combined with a random forest algorithm, an empirical relationship between stellar parameters and intrinsic ultraviolet color indices is established. By combining observed color indices, the study derives color excesses for 11,624,802 and 65,531 stars in the GALEX/near-UV and far-UV bands and for 336,633; 137,739; and 253,271 stars in the UVOT/uvw1, uvm2, and uvw2 bands, constructing corresponding ultraviolet extinction maps. Notably, the color excess data for the GALEX/near-UV band show a tenfold increase from previous results, with the extinction map covering approximately two-thirds of the sky at a resolution of 0 . ° 4. The typical uncertainties in the ultraviolet color excesses are 0.21 mag, 0.30 mag, 0.19 mag, 0.24 mag, and 0.21 mag for E NUV , G RP , E FUV , G RP , E u v w 1 , G RP , E u v m 2 , G RP , and E u v w 2 , G RP , respectively. By comparing the spatial distributions of R V derived from ultraviolet and Gaia optical band measurements with those obtained from infrared and optical data in previous works, it is evident that the R V distributions based on the ultraviolet data show noticeable differences, with some regions even exhibiting opposite trends. This suggests that a single-parameter R V extinction law may not be sufficient to simultaneously characterize the extinction behavior across infrared, optical, and ultraviolet bands.

Context. Three-dimensional maps of the Galactic interstellar medium are general astrophysical tools. Reddening maps may be based on the inversion of color excess measurements for individual target stars or on statistical methods using stellar surveys. Three-dimensional maps based on diffuse interstellar bands (DIBs) have also been produced. All methods benefit from the advent of massive surveys and may benefit from Gaia data. Aims. All of the various methods and databases have their own advantages and limitations. Here we present a first attempt to combine different datasets and methods to improve the local maps. Methods. We first updated our previous local dust maps based on a regularized Bayesian inversion of individual color excess data by replacing Hipparcos or photometric distances with Gaia Data Release 1 values when available. Secondly, we complemented this database with a series of ≃5000 color excess values estimated from the strength of the λ15273 DIB toward stars possessing a Gaia parallax. The DIB strengths were extracted from SDSS/APOGEE spectra. Third, we computed a low-resolution map based on a grid of Pan-STARRS reddening measurements by means of a new hierarchical technique and used this map as the prior distribution during the inversion of the two other datasets. Results. The use of Gaia parallaxes introduces significant changes in some areas and globally increases the compactness of the structures. Additional DIB-based data make it possible to assign distances to clouds located behind closer opaque structures and do not introduce contradictory information for the close structures. A more realistic prior distribution instead of a plane-parallel homogeneous distribution helps better define the structures. We validated the results through comparisons with other maps and with soft X-ray data. Conclusions. Our study demonstrates that the combination of various tracers is a potential tool for more accurate maps. An online tool makes it possible to retrieve maps and reddening estimations.

The interstellar magnetic field (ISMF) near the heliosphere is a basic part of the solar neighborhood that can only be studied using polarized starlight. Results of an ongoing survey of polarized starlight are analyzed with the goal of linking the interstellar magnetic field that shapes the heliosphere to the nearby field in interstellar space. New results for the direction of the nearby ISMF, based on a merit function that utilizes polarization position angles, identify several magnetic components. The dominant interstellar field, B_pol, is aligned with the direction L,B= 36.2,49.0 (+/-16.0) degrees and is within 8 degrees of the IBEX Ribbon ISMF direction. Stars tracing B_pol have the same mean distance as stars that do not trace B_pol, but show weaker polarizations consistent with lower column densities of polarizing grains. The variations in the polarization position angle directions indicate a low level of magnetic turbulence. B_pol is found after excluding polarizations that trace a separate magnetic structure that apparently is due to interstellar dust deflected around the heliosphere. Local interstellar cloud velocities relative to the LSR increase with the angles between the LSR velocities and ISMF, indicating that the kinematics of local interstellar material is ordered by the ISMF. Polarization and color excess data are consistent with an extension of Loop I to the solar vicinity. Polarizations are consistent with previous findings of more efficient grain alignment in low column density sightlines. Optical polarization and color excess data indicate the presence of nearby interstellar dust in the BICEP2 field. Color excess E(B-V) indicates an optical extinction of A_V about 0.59 mag in the BICEP2 field, while the polarization data indicate that A_V is larger than 0.09 mag. The IBEX Ribbon ISMF extends to the boundaries of the BICEP2 region.

Aims. Three-dimensional (3D) maps of the Galactic interstellar matter (ISM) are a potential tool of wide use, but accurate and detailed maps are still lacking. One of the ways to construct the maps is to invert individual distance-limited ISM measurements

Abstract The WEBDA database of open clusters (hereafter OCs) in the Galaxy contains 970 OCs, of which 911 have age determinations, 920 have distance measurements, and 911 have color-excess data. Base on the statistical analysis of global properties of open clusters, we investigate disk properties such as the height above the Galactic plane. We find that old open clusters (age ≥ 1 Gyr) are preferentially located far from the Galactic plane with 〈|z|〉~394.5 pc. They lie in the outer part of the Galactic disk. The young open clusters are distributed in the Galactic plane almost symmetrically with respect to the Sun, with a scale height perpendicular to the Galactic plane of 50.5 pc. The age distribution of open clusters can be fit approximately with a two-component exponential decay function: one component has an age scale factor of 225.2 Myr, and the other consists of longer-lived clusters with an age scale of 1.8 Gyr, which are smaller than those derived by Janes & Phelps (1994) of 200 Myr and 4 Gyr for the young and old OCs, respectively. As a consequence of completeness effects, the observed radial distribution of OCs with respect to Galactocentric distance does not follow the expected exponential profile. Instead, it falls off both for regions external to the solar circle and more sharply towards the Galactic Center, which is probably due to giant molecular cloud disruption in the center. We simulate the effects of completeness, assuming that the observed distribution of the number of OCs with a given number of stars above the background is representative of the intrinsic distribution of OCs throughout the Galaxy. Two simulation models are considered, in which the intrinsic number of the observable stars are distributed (i) assuming the actual positions of the OCs in the sample, and (ii) random selection of OC positions. As a result, we derive completeness-corrected radial distributions which agree with an exponential disk throughout the observed Galactocentric distance in the range of 5–15 kpc, with scale lengths in the range of 1.6–2.8 kpc.

The giant molecular clouds (GMCs) of external galaxies can be mapped with sub-arcsecond resolution using multiband observations in the near-infrared. However, the interpretation of the observed reddening and attenuation of light, and their transformation into physical quantities, is greatly hampered by the effects arising from the unknown geometry and the scattering of light by dust particles. We examine the relation between the observed near-infrared reddening and the column density of the dust clouds. In this paper we particularly assess the feasibility of deriving the mass function of GMCs from near-infrared color excess data. We perform Monte Carlo radiative transfer simulations with 3D models of stellar radiation and clumpy dust distributions. We include the scattered light in the models and calculate near-infrared color maps from the simulated data. The color maps are compared with the true line-of-sight density distributions of the models. We extract clumps from the color maps and compare the observed mass function to the true mass function. For the physical configuration chosen in this study, essentially a face-on geometry, the observed mass function is a non-trivial function of the true mass function with a large number of parameters affecting its exact form. The dynamical range of the observed mass function is confined to ~103.5 105.5 regardless of the dynamical range of the true mass function. The color maps are more sensitive in detecting the high-mass end of the mass function, and on average the masses of clouds are underestimated by a factor of ∼10 depending on the parameters describing the dust distribution. A significant fraction of clouds is expected to remain undetected at all masses. The simulations show that the cloud mass function derived from JHK color excess data using simple foreground screening geometry cannot be regarded as a one-to-one tracer of the underlying mass function.

view Abstract Citations (63) References (54) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Type IA Supernovae in Late Type Galaxies: Reddening Correction, Scale Height, and Absolute Maximum Magnitude della Valle, Massimo ; Panagia, Nino Abstract We have collected and analyzed the color excess data for the best photometrically studied type Ia supernovae (SNIa) which occurred in late type galaxies. From these data we find a ratio of the B band to selective extinction in the parent galaxies of R_B_ = A_B_/E(B-V)=3.35+/-0.25 (1σ). This indicates that the extinction curves in latetype galaxies have similar properties to that of our Galaxy. We obtain a new calibration for the absolute magnitude at maximum of SNIa in late type galaxies <M_B_> = - 19.24+/-0.18(1σ) + 5 log(H_0_/75), which is marginally brighter than the recent determinations for type Ia supernovae observed in elliptical (dust-free) galaxies, and appears to confirm the potential of SNIa as standard candles for distance determinations. Studying the distribution of the extinction in the parent galaxies we find an average half-width of selective extinction of {DELTA}[E(B-V)]=0.13+/-0.04 and a dispersion of extinction to SNe of σ[E(B-V)]=0.15+/-0.01. Allowing for extinction biases, the total width of the dust disk turns out to be 2τ_0_= 1.28+/-0.23 mag. These results imply that SNIa have a considerably broader distribution than the dust disk and confirm that they are older than old disk population objects, i.e., age > 1-2 billion years. Also, we conclude that total extinction thickness of late type galaxies is very similar to that of the Milky Way. Publication: The Astronomical Journal Pub Date: August 1992 DOI: 10.1086/116265 Bibcode: 1992AJ....104..696D Keywords: Elliptical Galaxies; Galactic Evolution; Interstellar Extinction; Stellar Magnitude; Supernovae; Computational Astrophysics; Milky Way Galaxy; Astrophysics; SUPERNOVAE: GENERAL; GALAXIES: INTERSTELLAR MATTER full text sources ADS | data products SIMBAD (45) NED (45)

Probable dust counterparts of arching structures are looked for in two cases, (a) the Eridanus expanding shell, Heiles (1976) and (b) the extended Sco-Cen feature, Weaver (1977). Apparently the color excess data may be used to derive distance and dimension estimates of these structures.

view Abstract Citations (14) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopic comparison of open clusters. II. The reddening, blanketing, and metallicity of NGC 2264. Barry, D. C. ; Cromwell, R. H. ; Schoolman, S. A. Abstract The spectral quantification procedure is used to determine the ratios of the metallic line blanketing of selected members of the young open cluster NGC 2264 to that of Hyades and Coma Cluster members. Intrinsic colors are determined by two independent analyses, one involving the Balmer lines and the other involving metallic features. The internal scatter in the determinations of both Fe/H and intrinsic colors is found to be remarkably small. Several interesting correlations are discovered which provide information on the nature of pre-main-sequence stars and demonstrate the value of quantitative spectroscopy even at moderate resolution. Specifically, the results show that: (1) the metallicity of NGC 2264 is the same as that of the Coma Cluster to within a few hundredths dex; (2) there is not evidence of an increase in the heavy-element abundance at the sun's galactocentric distance during the last 5 billion years; and (3) B-V color excesses are correlated with the distance (in magnitude) of an NGC 2264 member above the main sequence. Publication: The Astrophysical Journal Supplement Series Pub Date: September 1979 DOI: 10.1086/190611 Bibcode: 1979ApJS...41..119B Keywords: Early Stars; Interstellar Matter; Metallic Stars; Open Clusters; Red Shift; Stellar Spectra; Abundance; Balmer Series; Iron; Stellar Atmospheres; Stellar Envelopes; Stellar Gravitation; Stellar Luminosity; Ubv Spectra; Astrophysics; Color Excesses:Open Clusters; Interstellar Reddening:Open Clusters; Metal Abundances:Open Clusters full text sources ADS | data products SIMBAD (3)

view Abstract Citations (1) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Density Gradients in the Anticenter Region of the Milky way. McCuskey, S. W. Abstract Star counts to m = 17 in thirteen selected regions of the Milky Way between 1 = 142° and 1 = 184° at galactic latitude ØO have been used to obtain the space-density distribution of the stars in this anticenter portion of the galaxy. The number of stars involved is 42,000. The interstellar absorption has been evaluated from the color-excess data for the B stars published by Stebbiris, Huffer, and Whitford. In all areas an upper limit to the photographic absorption of 1.5-2.0 mag. is indicated. Over most of the region the absorption appears to set in abruptly at about 300-500 parsecs from the sun. In one longitude range, 1600_1730, however, the space is relatively clear by contrast. Here the absorption appears to set in at about 300 parsecs and increases at a rate of 0.4 mag/kpc outward from the sun. The density functions ~esu1ting from a numerical solution based on the standard van Rhijn luminosity function, modified by Luyten's proper-motion results, are indicated in Table 7. The striking features of the galactic structure in this region are: (a) a definite excess of absolutely bright stars at distances of less than 500 parsecs in 1 = 145° to 165°; (b) a high negative gradient in most of the area which reduces the density at 2500 parsecs to about 0.2 of that near the sun; and (c) an extensive region of relatively high density, 0.5-0.8, extending to 3000 parsecs in 1 = 175° to 185° Publication: The Astrophysical Journal Pub Date: July 1945 DOI: 10.1086/144737 Bibcode: 1945ApJ...102...32M full text sources ADS |