New HST/STIS optical spectra were obtained for a sample of early type stars with existing IUE UV spectra. These data were used to construct optical extinction curves whose general properties are discussed elsewhere. In this paper, we identify extinction features in the curves that are wider than diffuse interstellar bands (DIBs) but narrower than the well known broad band variability. This intermediate scale structure, or ISS, contains distinct features whose peaks can contribute a few percent to 20% of the total extinction. Most of the ISS variation can be captured by three principal components. We model the ISS with three Drude profiles and show that their strengths and widths vary from one sight line to another, but their central positions are stable, near 4370, 4870 and 6300A. The Very Broad Structure, VBS, in optical curves appears to be a minimum between the 4870 and 6300A absorption peaks. We find relations among the fit parameters and provide a physical interpretation of them in terms of a simplistic grain model. Finally, we note that the strengths of the 4370 and 4870A features are correlated to the strength of the 2175A UV bump, but that the 6300A feature is not, and that none of the ISS features are related to R(V). However, we verify that the broad band curvature of the continuous optical extinction is strongly related to R(V).
The 9.7$μ$m interstellar spectral feature, arising from the Si--O stretch of amorphous silicate dust, is the strongest extinction feature in the infrared (IR). In principle, the spectral profile of this feature could allow one to diagnose the mineralogical composition of interstellar silicate material. However, observationally, the 9.7$μ$m interstellar silicate extinction profile is not well determined. Here we utilize the Spitzer/IRS spectra of five early-type (one O- and four B-type) stars and compare them with that of unreddened stars of the same spectral type to probe the interstellar exti…
Interstellar extinction is investigated in a 1.5 square degree area in the direction of the reflection nebula NGC 7023 at l = 104.1 deg, b = +14.2 deg. The study is based on photometric classification and the determination of interstellar extinctions and distances of 480 stars down to V = 16.5 mag from photometry in the Vilnius seven-color system published in Paper I (2008). The investigated area is divided into five smaller subareas with slightly different dependence of the extinction on distance. The distribution of reddened stars is in accordance with the presence of two dust clouds at 282 …
Line-of-sight extinction estimates to well-studied young T Tauri and Herbig Ae/Be stars are based on many different measurements and analysis methods. This has resulted in wide scatter among the published $A_V$ values for the same star. In this work, we discuss the challenges in measuring extinction to actively accreting and especially outbursting young stellar objects (YSOs). We then explore a method not previously applied to young stars utilizing diffuse interstellar bands (DIBs). In early-type stars, narrow correlations exist between DIB equivalent widths and the column density of interstel…
Using diffuse interstellar bands (DIBs) at 5780 A, 5797 A and 6613 A, visible in the high resolution spectra, and measuring their equivalent widths, we estimate the interstellar extinction toward seven symbiotic stars. We find $E_{B-V}$= $1.28 \pm 0.10$ for AS 289, $E_{B-V}$= $1.55 \pm 0.10$ for BI Cru, $E_{B-V}$= $0.63 \pm 0.10$ for HD330036, $E_{B-V}$= $0.33 \pm 0.05$ for V2756 Sgr, $E_{B-V}$= $0.30 \pm 0.05$ for V2905 Sgr, $E_{B-V}$= $1.52 \pm 0.11$ for V417 Cen, $E_{B-V}$= $0.81 \pm 0.10$ for PN Sa 3-22. The derived values are in agreement with the extinction through the Galaxy.
I review the literature covering the issue of interstellar extinction toward the Milky Way bulge, with emphasis placed on findings from planetary nebulae, RR Lyrae, and red clump stars. I also report on observations from HI gas and globular clusters. I show that there has been substantial progress in this field in recent decades, most particularly from red clump stars. The spatial coverage of extinction maps has increased by a factor $\sim 100 \times$ in the past twenty years, and the total-to-selective extinction ratios reported have shifted by $\sim$20-25\%, indicative of the improved accura…
For more than 5000 stars with accurate parallaxes from the Hipparcos and Gaia DR1 Tycho-Gaia astrometric solution (TGAS), Tycho-2 photometry, interstellar polarization from eight catalogues and interstellar extinction from eight 3D maps the largest up to date comparison of the polarization and extinction is provided. The extinction maps give different estimations of the extinction and of the polarization efficiency as the polarization divided into extinction $P/A_V$ as well as of the percentage of the stars with the polarization efficiency higher than the limit of Serkowski $P/A_V>0.03$. Using…
A new analytical 3D model of interstellar extinction within 500 pc of the Sun as a function of the Galactic spherical coordinates is suggested. This model is physically more justified than the widely used Arenou model, since it takes into account the presence of absorbing matter both in the layer along the equatorial Galactic plane and in the Gould Belt. The extinction in the equatorial layer varies as the sine of the Galactic longitude and in the Gould Belt as the sine of twice the longitude in the Belt plane. The extinction across the layers varies according to a barometric law. It has been …
We produce a set of 72 NIR through UV extinction curves by combining new HST/STIS optical spectrophotometry with existing IUE spectrophotometry (yielding gapless coverage from 1150 to 10000 Angstroms) and NIR photometry. These curves are used to determine a new, internally consistent, NIR through UV Milky Way Mean Curve and to characterize how the shapes of the extinction curves depend on R(V). We emphasize that while this dependence captures much of the curve variability, there remains considerable variation which is independent of R(V). We use the optical spectrophotometry to verify the pres…
Spectropolarimetry is a powerful tool for diagnostic of interstellar matter and gives information on the geometry of the ejected material after the novae outbursts. In this paper are presented spectropolarimetric observations of the recurrent nova T CrB at quiescence obtained with FoReRo2 attached to the Cassegrain focus of the 2.0m RCC telescope of the Bulgarian Rozhen National Astronomical Observatory. The interstellar polarization toward T CrB was estimated using the field stars method. The spectropolarimetric observations were obtained from February 2018 to August 2021. In the wavelength r…
This review describes our current understanding of interstellar extinction. This differ substantially from the ideas of the 20th century. With infrared surveys of hundreds of millions of stars over the entire sky, such as 2MASS, SPITZER-IRAC, and WISE, we have looked at the densest and most rarefied regions of the interstellar medium at distances of a few kpc from the sun. Observations at infrared and microwave wavelengths, where the bulk of the interstellar dust absorbs and radiates, have brought us closer to an understanding of the distribution of the dust particles on scales of the Galaxy a…
A composite dust grain model which simultaneously explains the observed interstellar extinction, polarization, IR emission and the abundance constraints, is required. We present a composite grain model, which is made up of a host silicate oblate spheroid and graphite inclusions. The interstellar extinction curve is evaluated in the spectral region 3.4-0.1$μm$ using the extinction efficiencies of the composite spheroidal grains for three axial ratios. Extinction curves are computed using the discrete dipole approximation (DDA). The model curves are subsequently compared with the average observe…
Interstellar reddening corrections are necessary to reconstruct the intrinsic spectral energy distributions (SEDs) of accreting protostellar systems. The stellar SED determines the heating and chemical processes that can occur in circumstellar disks. Measurement of neutral hydrogen absorption against broad Lyman-$α$ emission profiles in young stars can be used to obtain the total H I column density (N(H I)) along the line of sight. We measure N(H I) with new and archival ultraviolet observations from the Hubble Space Telescope ($HST$) of 31 classical T Tauri and Herbig Ae/Be stars. The H I col…
We study the extinction properties of the composite dust grains, consisting of host silicate spheroids and graphite as inclusions, using discrete dipole approximation (DDA). We calculate the extinction cross sections of the composite grains in the ultraviolet spectral region, 1200Å-3200Åand study the variation in extinction as a function of the volume fraction of the inclusions. We compare the model extinction curves with the observed interstellar extinction curves obtained from the data given by the International Ultraviolet Explorer (IUE) satellite. Our results for the composite grains show …
Multicolor photometry from the Tycho-2 and 2MASS catalogues for 11 990 OB and 30 671 K-type red giant branch stars is used to detect systematic large-scale variations of the interstellar extinction law within the nearest kiloparsec. The characteristic of the extinction law, the total-to-selective extinction ratio $R_V$, which also characterizes the size and other properties of interstellar dust grains, has been calculated for various regions of space by the extinction law extrapolation method. The results for the two classes of stars agree: the standard deviation of the "red giants minus OB" $…
We probe the role of carbon in the ultraviolet (UV) extinction by examining the relations between the amount of carbon required to be locked up in dust [C/H]_dust with the 2175 Angstrom extinction bump and the far-UV extinction rise, based on an analysis of the extinction curves along 16 Galactic sightlines for which the gas-phase carbon abundance is known and the 2175 Angstrom extinction bump exhibits variable strengths and widths. We derive [C/H]_dust from the Kramers-Kronig relation which relates the wavelength-integrated extinction to the total dust volume. This approach is less model-depe…
There is growing observational evidence of dust coagulation in the dense filaments within molecular clouds. Infrared observations show that the dust grains size distribution gets shallower and the relative fraction of small to large dust grains decreases as the local density increases. Ultraviolet (UV) observations show that the strength of the 2175 Å feature, the so-called UV bump, also decreases with cloud density. In this work, we apply the technique developed for the Taurus study to the Orion molecular cloud and confirm that the UV bump decreases over the densest cores of the cloud as well…
The product of the previously constructed 3D maps of stellar reddening (Gontcharov 2010) and $R_V$ variations (Gontcharov 2012) has allowed us to produce a 3D interstellar extinction map within the nearest kiloparsec from the Sun with a spatial resolution of 50 pc and an accuracy of $0.2^m$. This map is compared with the 2D reddening map by Schlegel et al. (1998), the 3D extinction map at high latitudes by Jones et al. (2011), and the analytical extinction models by Arenou et al. (1992) and Gontcharov (2009). In all cases, we have found good agreement and show that there are no systematic erro…
Diffuse interstellar bands (DIBs) are broad absorption features measured in sightlines probing the diffuse interstellar medium. Although large carbon-bearing molecules have been proposed as the carriers producing DIBs, their identity remains unknown. The sight line to the young massive star-forming region M17 shows anomalous extinction in the sense that the total-to-selective extinction parameter differs significantly from the average Galactic value and may reach values $R_{V} > 4$. Given the high $R_V$ values, we investigate whether the DIBs in sight lines towards young OB stars in M17 show a…
We have applied the method of star counts with Wolf diagrams to determine the interstellar extinction in five Galactic cirri in Sloan Digital Sky Survey (SDSS) Stripe 82. For this purpose, we have used the photometry of stars in the GALEX NUV filter and the photometry of red dwarfs in five SDSS bands and four SkyMapper Southern Sky Survey DR2 bands. We have identified the cirri as sky regions with an enhanced infrared emission from the Schlegel+1998 map. The extinction in them has been calculated relative to the nearby comparison regions with a reduced emission. The results for different filte…
We have detected a broad interstellar absorption band centred close to 7700 Å and with a FWHM of 176.6$\pm$3.9 Å. This is the first such absorption band detected in the optical range and is significantly wider than the numerous diffuse interstellar bands (DIBs). It remained undiscovered until now because it is partially hidden behind the A telluric band produced by O$_2$. The band was discovered using STIS@HST spectra and later detected in a large sample of stars of diverse type (OB stars, BA supergiants, red giants) using further STIS and ground-based spectroscopy. The EW of the band is measu…
Based on the data obtained from the Spitzer/GLIPMSE Legacy Program and the 2MASS project, we derive the extinction in the four IRAC bands, [3.6], [4.5], [5.8] and [8.0] micron, relative to the 2MASS Ks band (at 2.16 micron) for 131 GLIPMSE fields along the Galactic plane within |l|<65 deg, using red giants and red clump giants as tracers. As a whole, the mean extinction in the IRAC bands (normalized to the 2MASS Ks band), A_[3.6]/A_Ks=0.63, A_[4.5]/A_Ks=0.57, A_[5.8]/A_Ks=0.49, A_[8.0]/A_Ks=0.55, exhibits little variation with wavelength (i.e. the extinction is somewhat flat or gray). This is …
We present a new version of our analytical model of the spatial interstellar extinction variations within the nearest kiloparsec. This model treats the 3D dust distribution as a superposition of three overlapping layers: (1) the layer along the Galactic midplane, (2) the layer in the Gould Belt, and (3) the layer passing through the Cepheus and Chamaeleon dust cloud complexes. In each layer the dust density decreases exponentially with increasing distance from the midplane of the layer. In addition, there are sinusoidal longitudinal extinction variations along the midplane of each layer. We ha…
The dust extinction laws and dust properties in M31 are explored with a sample of reddened O-type and B-type supergiants obtained from the LGGS. The observed spectral energy distributions (SEDs) for each tracer are constructed with multiband photometry from the LGGS, PS1 Survey, UKIRT, PHAT Survey, Swift/UVOT and XMM-SUSS. We model the SED for each tracer in combination with the intrinsic spectrum obtained from the stellar model atmosphere extinguished by the model extinction curves. Instead of mathematically parameterizing the extinction functions, the model extinction curves in this work are…
We investigate interstellar extinction curve variations toward $\sim$4 deg$^{2}$ of the inner Milky Way in $VIJK_{s}$ photometry from the OGLE-III and $VVV$ surveys, with supporting evidence from diffuse interstellar bands and $F435W,F625W$ photometry. We obtain independent measurements toward $\sim$2,000 sightlines of $A_{I}$, $E(V-I)$, $E(I-J)$, and $E(J-K_{s})$, with median precision and accuracy of 2%. We find that the variations in the extinction ratios $A_{I}/E(V-I)$, $E(I-J)/E(V-I)$ and $E(J-K_{s})/E(V-I)$ are large (exceeding 20%), significant, and positively correlated, as expected. H…
Traditionally, the effects of interstellar extinction on binary star light curves have been treated as a uniform reduction in the observed brightness of the system that is independent of orbital phase. However, unless the orbital plane of the system coincides with the plane of the sky, or if the two stars are completely identical and present with minimal mutual irradiation and tidal/rotational distortions, then this is unlikely to be an accurate representation of the effect of interstellar extinction. Here, we present an updated treatment of interstellar extinction as incorporated in the PHOEB…
We have studied the interstellar extinction in a field of 3' x 3' located about 6' SW of 30 Doradus in the Large Magellanic Cloud (LMC). Hubble Space Telescope observations in the U, B, V, I and Halpha bands reveal patchy extinction in this field. The colour-magnitude diagram (CMD) shows an elongated stellar sequence, almost parallel to the main sequence (MS), which is in reality made up of stars of the red giant clump (RC) spread across the CMD by the uneven levels of extinction in this region. Since these objects are all at the same distance from us and share very similar physical properties…
Supernova remnants (SNRs) embody the information of the influence on dust properties by the supernova explosion. Based on the color indexes from the 2MASS photometric survey and the stellar parameters from the SDSS$-$DR12$/$APOGEE and LAMOST$-$DR2$/$LEGUE spectroscopic surveys, the near-infrared extinction law and the distance of the Monoceros SNR are derived together with its nearby two nebulas -- the Rosette Nebula and NGC 2264. The distance is found at the position of the sharp increase of interstellar extinction with distance and the nebular extinction is calculated by subtracting the fore…
Depletion studies provide a way to understand the chemical composition of interstellar dust grains. We here examine 23 gamma-ray bursts (GRB) optical afterglow spectra (spanning 0.6<z<5.0) and compare their silicon and iron dust-phase column densities with different extinction curve parameters to study the composition of the interstellar dust grains in these high-redshift GRB host galaxies. The majority of our sample (87%) show featureless extinction curves and only vary in shape. We observe strong correlations (with >96% significance) between the total-to-selective extinction, R_V, and the du…
We present a three-dimensional (3D) extinction map of the southern sky. The map covers the SkyMapper Southern Survey (SMSS) area of $\sim$ 14,000 ${\rm deg^{2}}$ and has spatial resolutions between 6.9 and 27 arcmin. Based on the multi-band photometry of SMSS, the Two Micron All Sky Survey, the Wide-Field Infrared Survey Explorer Survey and the Gaia mission, we have estimated values of the $r$-band extinction for $\sim$ 19 million stars with the spectral energy distribution (SED) analysis. Together with the distances calculated from the Gaia data release 2 (DR2) parallaxes, we have constructed…
The Gaia GSP-Spec catalogue of interstellar extinctions, and stellar luminosities, radii, and masses
Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange（蔚蓝海岸大学、蔚蓝海岸天文台、法国国家科学研究中心、拉格朗日实验室）；I.N.A.F., Osservatorio Astronomico di Trieste（意大利国家天体物理研究所、的里雅斯特天文台）
We analyse an all-sky compilation of thirteen data sources with optical interstellar linear polarisation for 3871 {\it Gaia} DR2 and {\it Hipparcos} stars within 500 pc, which do not exhibit a considerable intrinsic polarisation. These data are analysed together with five 3D maps and models of the reddening $E(B-V)$. We consider variations of the polarisation degree $P$, position angle $θ$, and polarisation efficiency $P/E(B-V)$ with Galactic coordinates, distance $R$, and dereddened colour. $P$ shows a maximum at the Gould Belt mid-plane. $P/R$ drops in the Local Bubble by several times defin…
Extinction Distributions in Nearby Star-resolved Galaxies. II. M33
Qilu Normal University（齐鲁师范学院）；Shandong Key Laboratory of Space Environment and Exploration Technology（山东省空间环境与探月技术重点实验室）；Beijing Normal University（北京师范大学）；Yunnan University（云南大学）
The colour evolution of reddened Type Ia supernovae can place strong constraints on the location of dust and help address the question of whether the observed extinction stems from the interstellar medium or from circumstellar material surrounding the progenitor. Here we analyse BV photometry of 48 reddened Type Ia supernovae from the literature and estimate the dust location from their $B-V$ colour evolution. We find a time-variable colour excess $E(B-V)$ for 15 supernovae in our sample and constrain dust to distances between 0.013 and 45 pc ($4\times10^{16}-10^{20}$ cm). For the remaining su…
High-dispersion observations of the Na I D 5890, 5896 and K I 7665, 7699 interstellar lines, and the diffuse interstellar band at 5780 Angstroms in the spectra of 32 Type Ia supernovae are used as an independent means of probing dust extinction. We show that the dust extinction of the objects where the diffuse interstellar band at 5780 Angstroms is detected is consistent with the visual extinction derived from the supernova colors. This strongly suggests that the dust producing the extinction is predominantly located in the interstellar medium of the host galaxies and not in circumstellar mate…
