We constrain the light extinction properties of Milky Way dust. We investigated the correlations between dust column density as inferred from infrared data and the observed colours of celestial objects at cosmological distances with low levels of colour dispersion. Results derived using colours of quasars, brightest central galaxies, and luminous red galaxies are broadly consistent, indicating a proportionality constant between the reddening E(B-V)=A_B-A_V and the dust column density D^T (given in units of MJy/sr) of p=E(B-V)/D^T=0.02 and a reddening parameter R_V=A_V/E(B-V)=3 with fractional uncertainties of approximately 10%. The data do not provide any evidence for spatial variations in the dust properties, except for a possible hint of scatter in the dust extinction properties at the longest optical wavelengths.
The high cosmological precision offered by the next generation of galaxy surveys hinges on improved corrections for Galactic dust extinction. We explore the possibility of estimating both the dust extinction and large-scale structure from a single photometric galaxy survey, making use of the predictable manner in which Milky Way dust affects the measured brightness and colors of galaxies in a given sky location in several redshift bins. To test our method, we use a synthetic catalog from a cosmological simulation designed to model the Vera C. Rubin Observatory Legacy Survey of Space and Time. …
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…
Estimates of interstellar extinction are essential in a broad range of astronomical research. In the last decades, several maps and models of the large scale interstellar extinction in the Galaxy have been published. However, these maps and models have been developed in different programming languages, with different user interfaces and input/output formats, which makes using and comparing results from these maps and models difficult. To address this issue, we have developed a tool called GALExtin (\url{http://www.galextin.org}) - that estimates interstellar extinction based on both 3D models/…
Windows of low extinction in the Milky Way (MW) have been used along the past decades for the study of the Galactic structure and the stellar population across the inner bulge and disk. Here we report the analysis of another low extinction near-IR window discovered by the VISTA Variables in the Vía Láctea Survey. VVV WIN 1733$-$3349 is about half a degree in size and is conveniently located right in the MW plane, at Galactic coordinates $(l, b) = (-5.2, -0.3)$. The mean extinction of VVV WIN 1733$-$3349 is $A_{Ks} = 0.61\pm0.08$ mag, which is much smaller than the extinction in the surrounding…
We aim to compare variations in the full-UV dust extinction curve (912-3000 Angstrom), with the HI/H$_2$/total H content along diffuse Milky Way sightlines, to investigate possible connections between ISM conditions and dust properties. We combine an existing sample of 75 UV extinction curves based on IUE and FUSE data, with atomic and molecular column densities measured through UV absorption. The H$_2$ column density data are based on existing Lyman-Werner absorption band models from earlier work on the extinction curves. Literature values for the HI column density were compiled, and improved…
We develop a cosmological model for the evolution of dust grains in galaxies with a distribution of sizes in order to understand the origin of the Milky Way dust extinction curve. Our model considers the formation of active dust in evolved stars, growth by accretion and coagulation, and destruction processes via shattering, sputtering, and astration in the ISM of galaxies over cosmic time. Our main results follow. Galaxies in our cosmological model with masses comparable to the Milky Way's at z~0 exhibit a diverse range of extinction laws, though with slopes and bump strengths comparable to th…
Context. Several methods have been proposed to build 3D extinction maps of the Milky Way (MW), most often based on Bayesian approaches. Although some studies employed machine learning (ML) methods in part of their procedure, or to specific targets, no 3D extinction map of a large volume of the MW solely based on a Neural Network method has been reported so far. Aims. We aim to apply deep learning as a solution to build 3D extinction maps of the MW. Methods. We built a convolutional neural network (CNN) using the CIANNA framework, and trained it with synthetic 2MASS data. We used the Besançon G…
The position of the Sun inside the Milky Way's disc hampers the study of the spiral arm structure. We aim to analyse the spiral arms along the line-of-sight towards the Galactic centre (GC) to determine their distance, extinction, and stellar population. We use the GALACTICNUCLEUS survey, a JHKs high angular resolution photometric catalogue (0.2") for the innermost regions of the Galaxy. We fitted simple synthetic colour-magnitude models to our data via $χ^2$ minimisation. We computed the distance and extinction to the detected spiral arms. We also analysed the extinction curve and the relativ…
The extinction law from $0.9$ to $8$ microns in the inner $3\times3$ deg$^2$ of the Milky Way is measured using data from VISTA Variables in the Via Lactea, GLIMPSE and WISE. Absolute extinction ratios are found by requiring that the observed red clump density peaks at the GRAVITY collaboration distance to the Galactic centre. When combined with selective extinction ratios measured from the bulge giant colour-colour diagrams, we find an extinction law of $A_Z:A_Y:A_J:A_H:A_{K_s}:A_{W1}:A_{[3.6]}:A_{[4.5]}:A_{W2}:A_{[5.8]}:A_{[8.0]} =7.19(0.30):5.11(0.20):3.23(0.11):1.77(0.04):1:0.54(0.02):0.46…
We model dust evolution in Milky Way-like galaxies by post-processing the IllustrisTNG cosmological hydrodynamical simulations in order to predict dust-to-gas ratios and grain size distributions. We treat grain-size-dependent dust growth and destruction processes using a 64-bin discrete grain size evolution model without spatially resolving each galaxy. Our model broadly reproduces the observed dust--metallicity scaling relation in nearby galaxies. The grain size distribution is dominated by large grains at $z\gtrsim 3$ and the small-grain abundance rapidly increases by shattering and accretio…
We measured the mid-infrared (MIR) extinction using Spitzer photometry and spectroscopy (3.6--37 micron) for a sample of Milky Way sightlines (mostly) having measured ultraviolet extinction curves. We used the pair method to determine the MIR extinction that we then fit with a power law for the continuum and modified Drude profiles for the silicate features. We derived 16 extinction curves having a range of A(V) (1.8-5.5) and R(V) values (2.4-4.3). Our sample includes two dense sightlines that have 3 micron ice feature detections and weak 2175 A bumps. The average A(lambda)/A(V) diffuse sightl…
Interstellar dust extinction curves provide valuable information about dust properties, including the composition and size of the dust grains, and are essential to correct observations for the effects of interstellar dust. In this work, we measure a representative sample of near-infrared (NIR; 0.8-5.5 $μ$m) spectroscopic extinction curves for the first time, enabling us to investigate the extinction at wavelengths where it is usually only measured in broad photometric bands. We use IRTF/SpeX spectra of a sample of reddened and comparison stars to measure 15 extinction curves with the pair meth…
Mapping the Milky Way bulge at high resolution: the 3D dust extinction, CO, and X factor maps
三维星际消光图为恒星星族分析提供了有力的工具。我们使用的数据，从VISTA变量在通过Lactea调查与贝桑松恒星星族合成模型的银河系，以确定星际消光作为一个函数的距离在银河系的隆起覆盖$ -10 < l < 10$和$-10 < b <5$。我们采用了最近开发的方法来计算颜色过剩。首先，我们根据与2 MASS匹配的VVV星表构建了H-Ks vs. Ks和J-Ks vs. Ks色星等图。然后，根据M巨星的温度-颜色关系和距离-颜色关系，我们导出了消光系数随距离的变化。观察到的颜色被移动，以匹配贝桑松模型中的固有颜色，作为距离的函数。这就创建了一个三维的灭绝图：两个空间维度和一个距离维度，沿着每一条朝向凸起的视线。我们提出了一个三维消光图，覆盖整个VVV区域的分辨率为6' x 6'，使用距离箱为0.5千秒差距。测光的高分辨率和深度使我们能够推导出距离范围高达10千秒差距和高达30个$A_{V}$消光星等的消光图。综合地图显示了与其他2D地图相同的灰尘特征和一致的值。我们讨论了尘埃特征在视线中的空间分布，这表明在银河系酒吧前面有很多物质，特别是在5-7千秒差距之间。我们比较我们的尘埃消光图与高分辨率$\rm ^{12}CO$地图对银河系的隆起，在那里我们发现一个很好的相关性之间的$\rm ^{12}CO$和$\rm A_{V}$。我们通过结合CO图和尘埃消光图来确定X因子。我们导出的平均…
The 2175 Å ultraviolet (UV) extinction bump in interstellar medium (ISM) of the Milky Way was discovered in 1965. After intensive exploration of more than a half century, however, its exact origin still remains a big conundrum that is being debated. Here we propose a mixture model by which the extinction bump in ISM is argued possibly relevant to the clusters of hydrogenated T-carbon (HTC) molecules (C40H16) that have intrinsically a sharp absorption peak at the wavelength 2175 Å. By linearly combining the calculated absorption spectra of HTC mixtures, graphite, MgSiO3 and Fe2SiO4, we show tha…
Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS II. The complete high resolution extinction map and implications for Bulge studies
The Milky Way's nuclear stellar disc (NSD) and nuclear star cluster (NSC) are the main features of the Galactic centre. Nevertheless, their observation is hampered by the extreme source crowding and high extinction. Hence, their relation and formation scenario are not fully clear yet. We aim at detecting the stellar populations from the NSC and the NSD along the line-of-sight towards the NSC, and assess whether they have different stellar populations and star formation histories. We analysed the colour-magnitude diagram, $K_s$ vs. $H-K_s$, of a region of $8.2'\times2.8'$ centred on the NSC, an…
The nuclear stellar disc (NSD) is a dense stellar structure at the centre of our Galaxy. Given its proximity, it constitutes a unique laboratory to understand other galactic nuclei. Nevertheless, the high crowding and extinction hamper its study, and even its morphology and kinematics are not yet totally clear. In this work we use NSD red clump stars, whose intrinsic properties are well known, to trace the kinematics of the NSD and to compute the distance and extinction towards the edges of the NSD. We used publicly available proper motion and photometric catalogues of the NSD to distinguish r…
A first taste of MEAD (Measuring Extinction and Abundances of Dust) -- I. Diffuse Milky Way interstellar dust extinction features in JWST infrared spectra
Near-Infrared Variability Study of the Central 2.3 arcmin x 2.3 arcmin of the Galactic Centre II. Identification of RR Lyrae Stars in the Milky Way Nuclear Star Cluster
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…
We use two existing molecular cloud catalogs derived from the same CO survey and two catalogs derived from local dust extinction surveys to investigate the nature of the GMC mass-size relation in the Galaxy. We find that the four surveys are well described by $M_{GMC} \sim R^2$ implying a constant mean surface density, $Σ_{GMC}$, for the cataloged clouds. However, the scaling coefficients and scatter differ significantly between the CO and extinction derived relations. We find that the additional scatter seen in the CO relations is due to a systematic variation in $Σ_{GMC}$ with Galactic radiu…
The gas-to-dust ratio of reddened stars in the Milky Way (MW), the Magellanic Clouds, and in general is usually expressed as a linear relation between the hydrogen column density, N(H), and the reddening, E(B-V), or extinction in the V band (A(V)). If the extinction curve was truly universal, the strength of the relationship and the linearity would naturally be maintained for extinction at any wavelength, and also for N(H) vs. E(B-V). However, extinction curves vary within the Milky Way, and there is no reason why, except by chance, either E(B-V) or A(V) would be the most physical measure of d…
Large Variations Seen in First Ultraviolet Spectroscopic M33 Dust Extinction Curves
Space Telescope Science Institute（太空望远镜科学研究所）；Sterrenkundig Observatorium, Universiteit Gent（根特大学天文台）；Institute of Astronomy and NAO, Bulgarian Academy of Sciences（保加利亚科学院天体物理研究所）；University of Sofia, Faculty of Physics（索非亚大学物理学院）；Space Science Institute（空间科学研究所）；Department of Physics & Astronomy, Louisiana State University（路易斯安那州立大学物理与天文学系）；Maria Mitchell Association（玛丽亚·米切尔协会）；European Space Agency (ESA)（欧洲航天局）；Department of Physics & Astronomy, Johns Hopkins University（约翰斯·霍普金斯大学物理与天文学系）
Using photometric and spectroscopic data of Supernova (SN) 2012cu, a fairly reddened type Ia supernova, we derived its color excess curves and probed the dust extinction in its host galaxy, NGC 4772. In order to derive the extinction as a function of wavelength (i.e., $A_λ$), we model the color excess curves of SN 2012cu in terms of dust models consisting of silicate and carbonaceous (graphite or amorphous carbon) dust. The modeled extinction law towards SN 2012cu extends flatly to the far-ultraviolet (UV) bands, which is much flatter than those of the Milky Way and Magellanic Clouds, and the …
Interstellar dust plays a central role in shaping the detailed structure of the interstellar medium, thus strongly influencing star formation and galaxy evolution. Dust extinction provides one of the main pillars of our understanding of interstellar dust while also often being one of the limiting factors when interpreting observations of distant objects, including resolved and unresolved galaxies. The ultraviolet (UV) and mid-infrared (MIR) wavelength regimes exhibit features of the main components of dust, carbonaceous and silicate materials, and therefore provide the most fruitful avenue for…
