Context. Three dimensional interstellar extinction maps provide a powerful tool for stellar population analysis. However, until now, these 3D maps were rather limited by sensitivity and spatial resolution. Aims. We use data from the VISTA Variables in the Via Lactea survey together with the Besançon stellar population synthesis model of the Galaxy to determine interstellar extinction as a function of distance in the Galactic bulge covering −10 • < l < 10 • and −10 • < b < 5 • . Methods. We adopted a recently developed method to calculate the colour excess. First we constructed the H − Ks vs. Ks and J − Ks vs. Ks colour−magnitude diagrams based on the VVV catalogues that matched 2MASS. Then, based on the temperature−colour relation for M giants and the distance-colour relations, we derived the extinction as a function of distance. The observed colours were shifted to match the intrinsic colours in the Besançon model as a function of distance iteratively. This created an extinction map with three dimensions: two spatial and one distance dimension along each line of sight towards the bulge. Results. We present a 3D extinction map that covers the whole VVV area with a resolution of 6 × 6 for J − Ks and H − Ks using distance bins of 0.5 kpc. The high resolution and depth of the photometry allows us to derive extinction maps for a range of distances up to 10 kpc and up to 30 mag of extinction in A V (3.0 mag in A Ks ). Integrated maps show the same dust features and consistent values as other 2D maps. We discuss the spatial distribution of dust features in the line of sight, which suggests that there is much material in front of the Galactic bar, specifically between 5−7 kpc. We compare our dust extinction map with the high-resolution 12 CO maps (NANTEN2) towards the Galactic bulge, where we find a good correlation between 12 CO and A V . We determine the X factor by combining the CO map and our dust extinction map. Our derived average value X = 2.5 ± 0.47 × 10 20 cm −2 K −1 km −1 s is consistent with the canonical value of the Milky Way. The X-factor decreases with increasing extinction.

Whether the near-infrared (NIR) extinction law is universal has been a long debated topic. Based on the APOGEE H-band spectroscopic survey as a key project of SDSS-III, the intrinsic colors of a large number of giant stars are accurately determined from the stellar effective temperature. Taking this advantage and using a sample of 5942 K-type giants, the NIR extinction law is carefully re-visited. The color excess ratiorepresentative of the NIR extinction law, shows no dependence on the color excess when E(J − K S ) changes from ∼0.3 to ∼4.0, which implies a universal NIR extinction law from diffuse to dense regions. The constant value of E(J − H)/E(J − K S ), 0.64, corresponds to a power law index of 1.95. The other two ratios, E(H − K S )/E(J − K S ) and E(J − H)/E(H − K S ), are 0.36 and 1.78 respectively. The results are consistent with the MRN dust size distribution.

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We present a three dimensional extinction map in r band. The map has a spatial angular resolution, depending on latitude, between 3 -9 arcmin and covers the entire XSTPS-GAC survey area of over 6,000 deg 2 for Galactic longitude 140 ď l ď 220 deg and latitude´40 ď b ď 40 deg. By cross-matching the photometric catalog of the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anticentre (XSTPS-GAC) with those of 2MASS and WISE, we have built a multi-band photometric stellar sample of about 30 million stars and applied spectral energy distribution (SED) fitting to the sample. By combining photometric data from the optical to the near-infrared, we are able to break the degeneracy between the intrinsic stellar colours and the amounts of extinction by dust grains for stars with high photometric accuracy, and trace the extinction as a function of distance for low Galactic latitude and thus highly extincted regions. This has allowed us to derive the best-fit extinction and distance information of more than 13 million stars, which are used to construct the three dimensional extinction map. We have also applied a Rayleigh-Jeans colour excess (RJCE) method to the data using the 2MASS and WISE colour pH´W2q. The resulting RJCE extinction map is consistent with the integrated two dimensional map deduced using the best-fit SED algorithm. However for individual stars, the amounts of extinction yielded by the RJCE method suffer from larger errors than those given by the best-fit SED algorithm.

From previous samples of Red Supergiants (RSGs) by various groups, 191 objects are assembled to compose a large sample of RSG candidates in LMC. For 189 of them, the identity as a RSG is verified by their brightness and color indexes in several nearand mid-infrared bands related to the 2MASS JHKs bands and the Spitzer /IRAC and Spitzer /MIPS bands. From the visual time-series photometric observations by the ASAS and MACHO projects which cover nearly 8-10 years, the period and amplitude of light variation are analyzed carefully using both the PDM and Period04 methods. According to the properties of light variation, these objects are classified into five categories: (1) 20 objects are saturated in photometry or located in crowded stellar field with poor photometric results, (2) 35 objects with too complex variation to have any certain period, (3) 23 objects with irregular variation, (4) 16 objects with semi-regular variation, and (5) 95 objects with Long Secondary Period (LSP) among which 31 have distinguishable short period, and 51 have a long period shorter than 3000 days that can be determined with reasonable accuracy. For the semi-regular variables and the LSP variables with distinguishable short period, the period-luminosity relation is analyzed in the visual, near-infrared and mid-infrared bands. It is found that the P-L relation is tight in the infrared bands such as the 2MASS JHKs bands and the Spitzer /IRAC bands, in particular in the Spitzer /IRAC [3.6] and [4.5] bands; meanwhile, the P-L relation is relatively sparse in the V band which may be caused by the inhomogeneous interstellar extinction. The results are compared with others' P-L relationships for RSGs and the P-L sequences of red giants in LMC.

Context. Studies of the properties of the inner Galactic bulge strongly depend on the assumptions made about interstellar extinction. Most of the extinction maps available in the literature lack the information about the distance. Aims. We combine observations with the Besançon model of the Galaxy to investigate the variations of extinction along different lines of sight toward the inner Galactic bulge as a function of distance. In addition we study the variations in the extinction law in the bulge. Methods. We constructed color-magnitude diagrams with the following sets of colors: H-Ks and J-Ks from the VVV catalog and Ks- [3.6], , from GLIMPSE-II catalog matched with 2MASS. Using the newly derived temperature−color relation for M giants that match the observed color-magnitude diagrams better we then used the distance−color relations to derive the extinction as a function of distance. The observed colors were shifted to match the intrinsic colors in the Besançon model as a function of distance, thereby iteratively creating an extinction map with three dimensions: two spatial and one distance dimension along each line of sight toward the bulge. Results. Color excess maps are presented at a resolution of 15 × 15 for six different combinations of colors in distance bins of 1 kpc. The high resolution and depth of the photometry allows us to derive extinction maps to 10 kpc distance and up to 35 mag of extinction in A V (3.5 mag in A Ks ). Integrated maps show the same dust features and consistent values with the other 2D maps. Starting from the color excess between the observations and the model, we investigate the extinction law in near-infrared and its variation along different lines of sight.

The extinction laws at 7 µm and 15 µm are derived for more than 120 sightlines in the inner Galactic plane based on the ISOGAL survey data and the near-infrared data from DENIS and 2MASS. The tracers are the ISOGAL point sources with

A large number of carbon-rich evolved objects (asymptotic giant branch stars, protoplanetary nebulae, and planetary nebulae) in both the Milky Way galaxy and the Magellanic Clouds exhibit an enigmatic broad emission feature at ∼ 30 µm. This feature, extending from ∼ 24 µm to ∼ 45 µm, is very strong and accounts for up to ∼ 30% of the total infrared luminosity of the object. In literature it is tentatively attributed to magnesium sulfide (MgS) dust. Using the prototypical protoplanetary nebula around HD 56126 for illustrative purpose, however, in this work we show that in order for MgS to be responsible for the 30 µm feature, one would require an amount of MgS mass substantially exceeding what would be available in this source. We therefore argue that MgS is unlikely the carrier of the 30 µm feature seen in this source and in other sources as well.