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Context. The environment of Sagittarius A* (Sgr A*), the central black hole of the Milky Way, is the only place in the Universe where we can currently study the interaction between a nuclear star cluster and a massive black hole and infer the properties of a nuclear cluster from observations of individual stars.Aims. This work aims to explore the star formation history of the nuclear cluster and the structure of the innermost stellar cusp around Sgr A*.Methods. We combined and analysed multi epoch high quality AO observations. For the region close to Sgr A* we apply the speckle holography technique to the AO data and obtain images that are >= 50% complete down to K-s approximate to 19 within a projected radius of 5 '' around Sgr A*. We used H-band images to derive extinction maps.Results. We provide K-s photometry for roughly 39 000 stars and H-band photometry for similar to 11 000 stars within a field of about 40 '' x40 '', centred on Sgr A*. In addition, we provide K-s photometry of similar to 3000 stars in a very deep central field of 10 '' x10 '', centred on Sgr A*. We find that the K-s luminosity function (KLF) is rather homogeneous within the studied field and does not show any significant changes as a function of distance from the central black hole on scales of a few 0.1 pc. By fitting theoretical luminosity functions to the KLF, we derive the star formation history of the nuclear star cluster. We find that about 80% of the original star formation took place 10 Gyr ago or longer, followed by a largely quiescent phase that lasted for more than 5 Gyr. We clearly detect the presence of intermediate-age stars of about 3 Gyr in age. This event makes up about 15% of the originally formed stellar mass of the cluster. A few percent of the stellar mass formed in the past few 100 Myr. Our results appear to be inconsistent with a quasi-continuous star formation history. The mean metallicity of the stars is consistent with being slightly super solar. The stellar density increases exponentially towards Sgr A* at all magnitudes between K-s=15-19. We also show that the precise properties of the stellar cusp around Sgr A* are hard to determine because the star formation history suggests that the star counts can be significantly contaminated, at all magnitudes, by stars that are too young to be dynamically relaxed. We find that the probability of observing any young (non-millisecond) pulsar in a tight orbit around Sgr A* and beamed towards Earth is very low. We argue that typical globular clusters, such as they are observed in and around the Milky Way today, have probably not contributed to the nuclear cluster's mass in any significant way. The nuclear cluster may have formed following major merger events in the early history of the Milky Way. © ESO 2020, The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement no: [614922]. RS, FNL, EGC, ATGC, and BS acknowledge financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709). ATGC, BS, and RS acknowledge financial support from national project PGC2018-095049-B-C21 (MCIU/AEI/FEDER, UE). F. N.-L. gratefully acknowledges funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Project-ID 138713538 - SFB 881 ("The Milky Way System", subproject B8). This work is based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programmes IDs 083.B-0390, 183.B-0100 and 089.B-0162. We thank the staff of ESO for their great efforts and helpfulness.

Context. The distribution of stars around a massive black hole (MBH) has been addressed in stellar dynamics for the last four decades by a number of authors. Because of its proximity, the centre of the Milky Way is the only observational test case where the stellar distribution can be accurately tested. Past observational work indicated that the brightest giants in the Galactic centre (GC) may show a density deficit around the central black hole, not a cusp-like distribution, while we theoretically expect the presence of a stellar cusp. Aims. We here present a solution to this long-standing problem. Methods. We performed direct-summation N-body simulations of star clusters around massive black holes and compared the results of our simulations with new observational data of the GC's nuclear cluster. Results. We find that after a Hubble time, the distribution of bright stars as well as the diffuse light follow power-law distributions in projection with slopes of Γ ≈ 0.3 in our simulations. This is in excellent agreement with what is seen in star counts and in the distribution of the diffuse stellar light extracted from adaptive-optics (AO) assisted near-infrared observations of the GC. Conclusions. Our simulations also confirm that there exists a missing giant star population within a projected radius of a few arcsec around Sgr A∗. Such a depletion of giant stars in the innermost 0.1 pc could be explained by a previously present gaseous disc and collisions, which means that a stellar cusp would also be present at the innermost radii, but in the form of degenerate compact cores.© ESO, 2017., The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no. [614922]. PAS acknowledges support from the Ramon y Cajal Programme of the Ministry of Economy, Industry and Competitiveness of Spain. This work has been partially supported by the CAS President's International Fellowship Initiative.

Context. The existence of dynamically relaxed stellar density cusps in dense clusters around massive black holes is a long-standing prediction of stellar dynamics, but it has so far escaped unambiguous observational confirmation. Aims. In this paper we aim to revisit the problem of inferring the innermost structure of the Milky Way's nuclear star cluster via star counts, to clarify whether it displays a core or a cusp around the central black hole. Methods. We used judiciously selected adaptive optics assisted high angular resolution images obtained with the NACO instrument at the ESO VLT. Through image stacking and improved point spread function fitting we pushed the completeness limit about one magnitude deeper than in previous, comparable work. Crowding and extinction corrections were derived and applied to the surface density estimates. Known young, and therefore dynamically not relaxed stars, are excluded from the analysis. Contrary to previous work, we analyse the stellar density in well-defined magnitude ranges in order to be able to constrain stellar masses and ages. Results. We focus on giant stars, with observed magnitudes K = 12.5-16, and on stars with observed magnitudes K ≈ 18, which may have similar mean ages and masses than the former. The giants display a core-like surface density profile within a projected radius R ≤ 0.3 pc of the central black hole, in agreement with previous studies, but their 3D density distribution is not inconsistent with a shallow cusp if we take into account the extent of the entire cluster, beyond the radius of influence of the central black hole. The surface density of the fainter stars can be described well by a single power-law at R < 2 pc. The cusp-like profile of the faint stars persists even if we take into account the possible contamination of stars in this brightness range by young pre-main sequence stars. The data are inconsistent with a core-profile for the faint stars. Finally, we show that a 3D Nuker law provides a good description of the cluster structure. Conclusions. We conclude that the observed density of the faintest stars detectable with reasonable completeness at the Galactic centre, is consistent with the existence of a stellar cusp around the Milky Way's central black hole, Sagittarius A∗. This cusp is well developed inside the influence radius of Sagittarius A∗and can be described by a single three-dimensional power-law with an exponent γ = 1.43 ± 0.02 ± 0.1. This corroborates existing conclusions from Nbody simulations performed in a companion paper. An important caveat is that the faint stars analysed here may be contaminated significantly by dynamically unrelaxed stars that formed about 100 Myr ago. The apparent lack of giants at projected distances of R ≲ 0.3 pc (R ≲ 8″) of the massive black hole may indicate that some mechanism may have altered their distribution or intrinsic luminosity. We roughly estimate the number of possibly missing giants to about 100.© ESO 2017., The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement No. [614922].PAS acknowledges support from the Ramon y Cajal Programme of the Ministry of Economy, Industry and Competitiveness of Spain. This work has been partially supported by the CAS President's International Fellowship Initiative.

Context. The Milky Way nuclear star cluster (MWNSC) is a crucial laboratory for studying the galactic nuclei of other galaxies, but its properties have not been determined unambiguously until now.Aims. We aim to study the size and spatial structure of the MWNSC.Methods. This study uses data and methods that address potential shortcomings of previous studies on the topic. We use 0.2 '' angular resolution K-s data to create a stellar density map in the central 86.4 pc x 21 pc at the Galactic center. We include data from selected adaptive-optics-assisted images obtained for the inner parsecs. In addition, we use Spitzer/IRAC mid-infrared (MIR) images. We model the Galactic bulge and the nuclear stellar disk in order to subtract them from the MWNSC. Finally, we fit a Sersic model to the MWNSC and investigate its symmetry.Results. Our results are consistent with previous work. The MWNSC is flattened with an axis ratio of q=0.710.10, an effective radius of R-e=(5.1 +/- 1.0) pc, and a Sersic index of n=2.2 +/- 0.7. Its major axis may be tilted out of the Galactic plane by up to -10 degrees. The distribution of the giants brighter than the Red Clump (RC) is found to be significantly flatter than the distribution of the faint stars. We investigate the 3D structure of the central stellar cusp using our results on the MWNSC structure on large scales to constrain the deprojection of the measured stellar surface number density, obtaining a value of the 3D inner power law of gamma=1.38 +/- 0.06(sys)+/- 0.01(stat).Conclusions. The MWNSC shares its main properties with other extragalactic NSCs found in spiral galaxies. The differences in the structure between bright giants and RC stars might be related to the existence of not completely mixed populations of different ages. This may hint at recent growth of the MWNSC through star formation or cluster accretion.© ESO 2020, The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement n degrees[614922]. This work is based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programmes IDs 195.B-0283 and 091.B-0418. We thank the staff of ESO for their great efforts and helpfulness. N.N. acknowledges support by the Sonderforschungsbereich SFB 881 "The Milky Way System" of the German Research Foundation (DFG). F.N.-L. acknowledges financial support from a MECD pre-doctoral contract, code FPU14/01700. We acknowledge support by the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofisica de Andalucia (CSIC) (SEV-2017-0709).

From the Gaia mission, kinematic and star count data, together with the physical parameters of the stars - ages and metallicities-, will allow to characterise our Galaxy populations and, from that, the overall Galactic gravitational potential. One of the promising procedures to reach such goal will be to optimise the present Population Synthesis models by fitting, through robust statistical techniques, the large and small scale structure and kinematics parameters that best will reproduce Gaia data. As a first step we present here the comparison between the data from the Tycho-2 catalogue and the Besancon Galaxy Model simulations, as well as our present and future work on the model optimization.

Context. Thanks to recent large scale surveys in the near infrared such as 2MASS, the galactic plane that most suffers from extinction is revealed and its overall structure can be studied. Aims. This work aims at constraining the structure of the Milky Way external disc as seen in 2MASS data, and in particular the warp. Methods. We use the Two Micron All Sky Survey (hereafter 2MASS) along with the Stellar Population Synthesis Model of the Galaxy, developed in Besancon, to constrain the external disc parameters such as its scale length, its cutoff radius, and the slope of the warp. In order to properly interpret the observations, the simulated stars are reddened using a three dimensional extinction map. The shape of the stellar warp is then compared with previous results and with similar structures in gas and dust. Results. We find new constraints on the stellar disc, which is shown to be asymmetrical, similar to observations of HI. The positive longitude side is found to be easily modelled with a S shape warp but with a slope significantly smaller than the slope seen in the HI warp. At negative longitudes, the disc presents peculiarities which are not well reproduced by any simple model. Finally, comparing with the warp seen in the dust, it seems to follow a slope intermediate between the gas and the stars., 9 pages. Accepted for publication in Astronomy and Astrophysics

Over the last decade there have been a series of results supporting the hypothesis of the existence of a long thin bar in the Milky Way with a half-length of 4.5 kpc and a position angle of around 45 deg. This is apparently a very different structure from the triaxial bulge of the Galaxy, which is thicker and shorter and dominates the star counts at |l, (8 pages, 14 figures, accepted for publication in A&A)

The gas distribution and dynamics in the inner Galaxy present many unknowns as the origin of the asymmetry of the longitude-velocity (lv) diagram of the Central Molecular Zone (CMZ). On the other hand, there are recent evidences in the stellar component of the presence of a nuclear bar that could be slightly lopsided. Our goal is to characterize the nuclear bar observed in 2MASS maps and to study the gas dynamics in the inner Milky Way taking into account this secondary bar. We have derived a realistic mass distribution by fitting 2MASS star counts maps with three components (disk, bulge and nuclear bar) and we have simulated the gas dynamics, in the deduced gravitational potential, using a sticky-particles code. Our simulations of the gas dynamics reproduce successfully the main characteristics of the Milky Way for a bulge orientation of 20-35 deg with respect to the Sun-Galactic Center (GC) line and a pattern speed of 30-40 km/s/kpc. In our models the Galactic Molecular Ring (GMR) is not an actual ring but the inner parts of the spiral arms, while the 3-kpc arm and its far side counterpart are lateral arms that contour the bar. Our simulations reproduce, for the first time, the parallelogram shape of the lv-diagram of the CMZ as the gas response to the nuclear bar. This bar should be oriented by an angle of ~60-75 deg with respect to the Sun-GC line and its mass amounts to (2-5.5)10e9 Msun. We show that the observed asymmetry of the CMZ cannot be due to lopsidedness of the nuclear bar as suggested by the 2MASS maps. We do not find clear evidences of lopsidedness in the stellar potential. We propose that the observed asymmetry of the central gas layer can be due to the infalling of gas into the CMZ in the l=1.3-complex, 28 pages, 6 tables, 14 figures. To appear in Astronomy and Astrophysics

We have carried out deep R , I , CN, TiO observations of the dwarf irregular galaxy DDO 190. We confirm the existence of an intermediate-age population around this galaxy. The identification of 47 carbon stars seen up to 5 arcmin from the centre of the galaxy implies that the population distribution of DDO 190 is similar to those found in some other Local Group dIrr galaxies. An estimate of the metallicity, [Fe/H] = -1.55 ± 0.12, is obtained based on the observed C/M ratio. From the analysis of star counts, corrected for the radial variation of the incompleteness level, we determine a scale-length α = 40 ± 5'' , in agreement with the recent literature.

e present wide field deep UBVI photometry for the previously unstudied open cluster NGC 4852 down to a limiting magnitude $I\sim24$, obtained from observations taken with the Wide Field Imager camera on-board the MPG/ESO 2.2m telescope at La Silla (ESO, Chile). These data are used to obtain the first estimate of the cluster basic parameters, to study the cluster spatial extension by means of star counts, and to derive the Luminosity (LF) and Mass Function (MF). The cluster radius turns out to be $5.0\pm1.0$ arcmin. The cluster emerges clearly from the field down to V=20 mag. At fainter magnitud es, it is completely confused with the general Galactic disk field. The stars inside this region define a young open cluster (200 million years old) 1.1 kpc far from the Sun (m-M = 11.60, E(B-V) = 0.45). The Present Day Mass Functions (PDMF) from the $V$ photometry is one of the most extended in mass insofar obtained, and can be represented as a power-law with a slope $\alpha = 2.3\pm0.3$ and (the Salpeter (1955) MF in this notation has a slope $\alpha = 2.35$), in the mass range $3.2 \leq \frac{m}{m_{\odot}} \leq 0.6$. Below this mass, the MF cannot be considered as representative of the cluster MF, as the cluster merges with the field and therefore the MF is the result of the combined effect of strong irregularities in the stellar background and interaction of the cluster with the dense Galactic field. The cluster total mass at the limiting magnitude results to be 2570$\pm$210 M$_{\odot}$., Comment: 9 pages, 10 eps figures (some degraded in resolution), accepted for publication in A&A

This paper presents a critical reassessment of the C/M ratio in the Local Group galaxies that have been surveyed by us in the last few years. We update distances, reddenings and metallicities with particular care to obtain coherent values for each galaxy. A new equation for the bolometric correction of M stars in terms of their (R − I) colours is obtained from Bessell et al. (1998) data. We present a critical discussion on the colour - spectral type relation for M stars which reveals a dramatic lack of reliable data for late M stars. Finally, we show that - when homogeneous data are used - the log(C/M0+) is well correlated to the (Fe/H) of the parent galaxy. Early objective prism surveys of the Milky Way revealed that C stars and late M stars were not spatially distributed in the same way. Blanco (1965) showed that M stars are found pref- erentially inside the Sun's orbit while C stars favor the anti- center region. Westerlund (1965) also noticed that late M stars are much more numerous toward the Galactic center. More than ten years later, when deep late-type star surveys of the Magellanic Clouds were initiated, a pronounced difference be- tween galaxies was discovered. Blanco et al. (1978) were the first to point out the tremendous differences between the ratio of the number of C stars and of late M stars in the Galactic bulge, in the Large Magellanic Cloud (LMC) and in the Small Magellanic Cloud (SMC). They rightly suggested that the ra- tios were anti-correlated with the metal abundance. Iben & Renzini (1983) gave two reasons to explain the trend of the C/M ratio with the abundance of the parent pop- ulation. First, the effect of the carbon dredge-up on the stellar spectrum is more pronounced for stars of low metallicity: it is easier to transform an O-rich star into a C-rich star when there is little oxygen to start with. Second, the giant branch of metal- poor systems is steeper, therefore bluer than the metal-rich one, thus there are few if any M or late M stars in very metal-poor systems.

We present a large-scale study of the IC1396 region using new deep NIR and optical images, complemented by 2MASS data. For ten globules in IC1396 we determine (H-K, J-H) colour-colour diagrams and identify the young stellar population. Five of these globules contain a rich population of reddened objects, most of them probably young stellar objects. Two new HH objects (HH865 and HH864) could be identified by means of [SII] emission, one of them a parsec-scale flow. Using star counts based on 2MASS data we create an extinction map of the whole region. This map is used to identify 25 globules and to estimate their mass. The globule masses show a significant increase with the distance from the exciting O6.5V star HD206267. We explain this correlation by the enhanced radiation pressure close to this star, leading to evaporation of the nearby clouds and hence smaller globule masses. We see evidence that the radiation from HD206267 has a major impact on the star formation activity in these globules., Comment: 13 pages, 14 figures, A&A accepted, version with high resolution figures at http://www.dias.ie/~df/

In this article we study the N83-84-85 region of the inner wing of the SMC. Direct and low-dispersion objective prism plates taken with the 1.2 m UK Schmidt Telescope have been digitized by the SuperCOSMOS machine. Star counts have been performed for our region in selected luminosity slices in the U filter and isodensity contours have been used to identify the structures with enhanced stellar number density. We find evidence of triggered star formation from massive stars of older to more recent OB associations. Circular arcs constructed by O and B stars have been detected. A study of the population places stars with more recent ages in the groups of the arcs than of their centers. These effects can be explained by supernova explosions. A catalogue of the non-saturated detected OB stars in this region is given.

We present CCD photometry in the Washington system C and T1 passbands down to T1 ∼ 18.5 mag in the field of Tombaugh 1, a little studied open cluster located in the third Galactic quadrant. We measured T1 magnitudes and C −T1 colours for a total of 1351 stars distributed throughout an area of 13. 6 × 13. 6. A cluster radius of 4. 3 ± 0. 3 was estimated from star counts in 100-pixel a side boxes distributed throughout the entire observed field. Based on the best fits of isochrones computed by the Geneva group for Z = 0.008 to the T1 vs. C − T1 colour–magnitude diagram, we derive a colour excess E(C − T1) = 0.55 ± 0.10, equivalent to E(B − V) = 0.30 ± 0.05, a distance of (2.2 ± 0.5) kpc from the Sun and an age of 1.3 +0.1 −0.2 Gyr. The latter value is in good agreement with that derived from the independent metallicity δT1 index defined in Geisler et al. (1997, AJ, 114, 1920). An independent metallicity estimation using the [MT1 , (C − T1)0] plane with the standard giant branches of Geisler & Sarajedini (1999, AJ, 117, 308) yields [Fe/H] = −0.30 ± 0.25 dex, a value which lends support to the one obtained from the isochrone fit. Tombaugh 1 is then found to be a relatively metal-poor intermediate-age open cluster. Fil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina Fil: Claria Olmedo, Juan Jose. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina Fil: Ahumada, Andrea Veronica. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina

We have obtained CCD photometry in the Johnson V, Kron-Cousins I and CT1 Washington systems for NGC 2324, a rich open cluster located ∼35 ◦ from the Galactic anticentre direction. We measured V magnitudes and V − I colours for 2865 stars and T1 magnitudes and C − T1 colours for 1815 stars in an area of 13. 6 × 13. 6. The comparison of the cluster colour-magnitude diagrams with isochrones of the Geneva group yield E(V − I) = 0.33 ± 0.07 and V − MV = 13.70 ± 0.15 for log t = 8.65 (t = 440 Myr) and Z = 0.008 ((Fe/H) = −0.40), and E(C − T1) = 0.40 ± 0.10 and T1 − MT 1 = 13.65 ± 0.15 for the same age and metallicity level. The resulting E(V − I) reddening value implies E(B − V) = 0.25 ± 0.05 and a distance from the Sun of (3.8 ± 0.5) kpc. Star counts carried out within and outside the cluster region allowed us to estimate the cluster angular radius as 5. 3 ± 0. 3 (5.9 pc). When using the E(B − V) reddening value here derived and the original Washington photometric data of Geisler et al. (1991) for the stars confirmed as red cluster giants from Coravel radial velocities, we found (Fe/H) = −0.31 ± 0.04, which is in good agreement with the best fits of isochrones. Therefore, NGC 2324 is found to be a relatively young, metal-poor and distant open cluster located beyond the Perseus spiral arm. A comparison of NGC 2324 with 10 well-known open clusters of nearly the same age shows that the cluster metal abundance and its position in the Galaxy are consistent with the existence of a radial abundance gradient of −0.07 dex kpc −1 in the Galactic disc.

We used the CFH12K wide field camera to survey the carbon star population of NGC 185 using the CN-TiO technique. 145 C stars are identified with a mean $\langle I \rangle = 19.99\pm0.05$, corresponding to $\langle M_I\rangle = -4.41\pm0.05$, a mean luminosity similar to what was recently found for the C star population of NGC 147. The stellar surface density profile of NGC 185 follows a power law with an exponential scale length of 2.53 ± 0.07 ' . The surface density of C stars follows also a power law but with a smaller scale length, $1.56 \pm 0.06$, demonstrating that the intermediate-age population of NGC 185 is more concentrated than its old population. A tidal radius, $r_{\rm t} = 22.5\pm2.2'$ is determined from red giant star counts. The C/M ratio of NGC 185 is $0.17 \pm 0.02$ with no apparent sign of a radial gradient. We compare the carbon star populations of NGC 185 and NGC 147 to conclude that it is unlikely that they form a close pair.

We have cross-correlated 2MASS and DENIS point sources in 17 galactic fields in order to find systematic astrometric or photometric shifts between the surveys. No significant differences have been found between the data of the two filters in common ( J and K s ). This allows to combine data from the two surveys for a further analysis of galactic structure via star counts.

The fundamental integral equation of stellar statistics represents a direct, model-independent approach to calculating stellar densities. Many techniques exist for its solution, but some of these require assumptions, such as a Gaussian luminosity function or a specific form for the density function, that may be unrealistic. To solve the equation as an undeterdetermined total least squares system with Tikhanov regularization recognizes that the problem is ill-posed and generally ill-conditioned as well and oers decided advantages: it is unnecessary to assume a Gaussian luminosity function nor a specific form for the density function; discretization error in the kernel of the integral equation as well as the Poisson error in the star counts are accounted for; mean errors for the densities are calculated; the densities are constrained to be both continuous and positive. The greatest drawback to the method comes from the selection of the ridge parameter, but the drawback becomes surmountable. The method is first applied to three examples, general star counts, the distribution of K0 giants, and the distribution of M 2-M 4 dwarfs, and compared with densities calculated from methods such as Malmquist's and the ( m ,l og) table. Regularized total least squares competes well with these methods. Then the method is applied to a new data set from the AC2000.2 catalog to calculate the densities of M giants and supergiants in the directions of the north and south galactic poles. The densities decrease exponentially to near zero at 2000 pc, with half-density points near 550 pc: No evidence for asymmetry between the two hemispheres can be seen.

We have pursued two different methods to analyze the old stellar population near the Galactic plane, using data from the 2MASS survey. The first method is based on the isolation of the red clump giant population in the color-magnitude diagrams and the inversion of its star counts to obtain directly the density distribution along the line of sight. The second method fits the parameters of a disc model to the star counts in 820 regions. Results from both independent methods are consistent with each other. The qualitative conclusions are that the disc is well fitted by an exponential distribution in both the galactocentric distance and height. There is not an abrupt cut-off in the stellar disc (at least within R6 kpc) that: the scale-height in the solar circle is h_z(R_sun)=3.6e-2 R_sun, the scale-length of the surface density is h_R=0.42 R_sun and the scale-length of the space density in the plane (i.e. including the effect of the flare) is H=0.25 R_sun. The variation of the scale-height due to the flare follows roughly a law h_z(R) =~ h_z(R_sun) exp [(R-R_\odot)/([12-0.6R(kpc)] kpc)] (for R, Comment: LaTEX, 20 pages, 23 figures, accepted to be published in A&A

We present the results of optical and near-IR spectroscopic and broadband multicolour photometric observations of the emission-line star AS 381. Its properties were found to be similar to those of Be stars with warm dust, a group of galactic objects recently defined by Sheikina et al. (2000). The spectrum of AS 381 indicates the presence of both a hot (early B-type) and a cool (K-type) star in the system.

Carina is a small and faint classical dwarf spheroidal galaxy in the halo of the Milky Way with a highly episodic star formation history (e.g., Hurley-Keller et al. 1998). Using VLT/FLAMES in high resolution mode, we significantly increase the sample of stars with abundance determinations in Carina, adding to earlier work with UVES. Here we present our preliminary abundances for Fe, Mg, Ca and Ba in 23 red giant branch stars in the centre of Carina.

We report the discovery of a new conspicuous flare star coincident with the position of the IRAS PSC source 18456-0223 that is located in or projected on a dark cloud. In the immediate vicinity of the source, a very faint nebula and a small group of stars are detected in the optical. We carried out rough red band photometry and accurate astrometry of those stellar objects. In addition, near-infrared images were obtained with the DENIS survey instrument in I (0.8), J (1.25) and K s (2.15 μ m) that show an increasing number of stars which appear to constitute a small cluster around the position of the IRAS source; the flare star itself ($R_{\rm MAX} \approx$ 15 fraction of minute55, $R_{\rm MIN} > $ 22 fraction of minute5) however, could not be traced. We assume that the flare star is enshrouded in a dust cloud of $A_{V}> 10^{\rm m}$. By using a K vs. $J-K$ diagram we were able to detect a new star forming region around IRAS 18456-0223 by identifying a number of YSO candidates. The distance estimate is $1600\pm400$ pc and that of the foreground extinction $A_{V} = 2\pm0.5$ mag.

An analysis of the Hipparcos photometry of HD 115071 shows that it is an ellipsoidal variable with a period of 2.73126 days, twice that suggested previously. Modelling the light curve combined with the available radial velocities suggests that the more massive, hotter component is smaller and less luminous than the cooler component, which is probably filling its Roche lobe. The likely age of the system indicates that it is a MS + MS blue straggler, created by Case A mass exchange.

We discuss star count and three-color data for the two inner-Galaxy elds SA 107 and NGC 6171 observed in the new Basel RGU high-latitude eld star survey. Our analysis is based on the structural models of the Galactic population components that were derived from the previous studies of seven elds mainly in the outer Galaxy (Buser et al. 1998, 1999, hereafter Papers I and II, respectively). Apart from the canonical structural parameters, we here explore some of the special conditions prevailing in the transition region from high to low latitudes approaching the Galactic bulge, such as interstellar reddening, preponderant sampling of giants, and pos- sible large-scale radial metallicity gradients. We show that the data are consistent on a high condence level with a model incorporating an old-thin disk with local mean metallicityh(M=H)i = 0:13 0:21 dex at galactocentric distance R 7:3 kpc and radial abundance gradient @(M=H)=@x = 0:078 0:016 dex/kpc, and a thick disk with mean metallicityh(M=H)i = 0:730:15 dex and vertical metallicity gradient@(M=H)=@z = 0:070:03 dex/kpc. Any radial gradient of the thick disk is shown to be marginal, 0 @(M=H)=@x 0:02 dex/kpc. For the inner halo, we nd a gradient-less metal-weak component with mean metallicity h(M=H)i 1:8 0:3 dex but also evidence of a { possibly localized { metal-rich component havingh(M=H)i = 1:0 0:2 dex. These results provide an important further step toward a comprehensive and detailed mapping of the larger-scale density and metallicity structures of the Galaxy, to be derived from the full-survey data in 14 elds.

We present ground-based multi-colour Geneva photometry and high-resolution high S/N spectra of the variable B-type star HD 105382. We provide evidence that this star is not a Be star, as indicated in the literature. The monoperiodic variability found in the Hipparcos data is confirmed in our ground-based follow-up observations. All existing data give rise to the detection of the period of 1.295 days. We try to interpret the variability of the star in terms of a non-radial g-mode pulsation model and of a rotational modulation model. None of these two is able to explain the observed line-profile variations in full detail.

We present uvby - β photometry of 116 X-ray flux-selected active stars in the directions of the Orion (40), Taurus-Auriga (58) and Scorpius OB2-2 (18) star forming regions. Additionally, we give near IR JHK photometry of 20 active stars in the Taurus-Auriga direction. The program stars were selected from the ROSAT All Sky Survey and EINSTEIN X-ray surveys and are spectroscopically confirmed weak-line T Tauri stars and weak-line T Tauri star candidates. The photometry confirms the young nature of the program stars and also indicates that a significant fraction of the sample could be foreground objects. The data given here probably represent the largest homogeneous uvby - β photometric sample of new WTTS and WTTS candidates. Many objects in the sample are observed photometrically for the first time.

Strmgren and H photometry of 130 stars in the Carina section of the Milky Way is presented. The color excesses and the distances of all stars are obtained. A good agreement is found between the CM and HR dia- grams and the spatial distribution of these stars.

We reanalyze deep star counts in five CADIS fields. The data are presented as vertical density distributions of stars perpendicular to the Galactic plane. In three fields the profiles are consistent with each other, while in two fields significant overdensities of stars are found. The overdensity in one field can be associated with the Virgo overdensity which can be traced right into the disk of the Milky Way. Using this detection we estimate the mass of the Virgo overdensity and show that this is equivalent to the stellar content of a Local Group dwarf spheroidal galaxy. The overdensity in the second field is more difficult to associate with a previously known overdensity. We suggest that it is related both to the Monoceros stream and the recently discovered Orphan stream., 4 pages, 3 figures, accepted as Research Note by Astron. Astrophys

Using absolute proper motions derived from APM measurements of Tautenburg, Palomar and UK Schmidt plates (cf. Scholz et al. 1996) we determined membership probabilities of the globular cluster M 5 in a four-dimensional space of proper motions and coordinates. The solution for 19 unknown parameters was obtained by the maximum likelyhood method. Dierent mean absolute proper motions and dispersions were found for three dis- tribution functions of the cluster stars, near eld stars and distant eld stars. In addition to the four-dimensional dis- tribution functions, we also investigated two-dimensional distribution functions including either only the proper mo- tions or only the coordinates. We compared the results with the colour-magnitude diagram obtained from a B;V photographic photometry using two of the Tautenburg plates and with the membership determination of Rees (1993). In comparison to the last work based on observa- tions with larger epoch dierences and better astrometric scale, our results are less accurate but extend the mem- bership investigation of M 5 to fainter stars (B = 19) and to the outer regions of the cluster. The full APM scans of the dierent Schmidt plates were also used for star counts applying a crowding correction in the central cluster re- gion based on the area of crowded images and on the stel- lar luminosity function in the outer cluster region. The tidal radii from tting King proles to the counts of all objects on the plates and of the cluster members are dis- cussed. From the deep counts of the full scans we found an indication of a tidal tail around M 5 (cf. Grillmair et al. 1995). However, this eect was not conrmed by the member counts.

We present the results of monitoring of a sample of T Tauri stars. The method of differential CCD photometry was applied. The observations span a range of ten days and show that eleven out of twelve sources varied during this time interval. These variations are correlated in all bands. Periods were detected (confidence level 99.99%) for eight out of eleven variable stars; one additional period was found at the 99.9% confidence level. Of those, one (BP Tau) agrees with previously published periods; two, GM Aur and IQ Tau, do not; six are new detections of periodicities. The sample is drawn from the Taurus-Auriga and Cepheus IV star-forming regions.

Galactic structure studies involve the manipulation of star catalogues and their global comparison with sophisticated synthesis models. In this paper, we present a detailed multivariate star count analysis algorithm. By combining the photometric and kinematic information, it performs a global analysis of the multivariate star counts including magnitude, colours, and proper motions. The method allows us to constrain galactic structure parameters and derive the relative densities of different components and populations in the Galaxy. Monte Carlo simulations have been carried out to demonstrate the viability of the method. A simple example of application to real star count data is given. We found the asymmetric drift of the thick disk to be 80 f 10 km s-l at a 3 sigma level. Detailed investigations from a complete survey of several galactic directions are in preparation.

We present a self-consistent vertical disc model of thin and thick disc in the solar vicinity. The model is optimized to fit the local kinematics of main sequence stars by varying the star formation history and the dynamical heating function. The star formation history and the dynamical heating function are not uniquely determined by the local kinematics alone. For four different pairs of input functions we calculate star count predictions at high galactic latitude as a function of colour. The comparison with North Galactic Pole data of SDSS/SEGUE leads to significant constraints of the local star formation history. In (2) we published a self-consistent vertical disc model of thin and thick disc in the solar cylinder. The thin disc model is based on a series of stellar subpopulations with surface densities and velocity dispersions according to an adopted star formation history (SFR) and a dynamical heating function (AVR). An isothermal thick disc component is included self-consistently. The discs are in dynamical equilibrium including the gravitational forces of the gas component and the dark matter halo. A simple chemical enrichment model is included to reproduce the metallicity distribution of the G-dwarfs in the solar neighbourhood. The SFR and AVR are varied in order to fit the local kinematics of main sequence (MS) stars and to match other constraints of the local stellar disc. We selected four models fitting the local kinematics equally well, but the SFR cannot be determined by the local kinematics alone (top panels of Fig. 1).

International audience; From the Gaia mission, kinematic and star count data, together with the physical parameters of the stars - ages and metallicities-, will allow to characterise our Galaxy populations and, from that, the overall Galactic gravitational potential. One of the promising procedures to reach such goal will be to optimise the present Population Synthesis models by fitting, through robust statistical techniques, the large and small scale structure and kinematics parameters that best will reproduce Gaia data. As a first step we present here the comparison between the data from the Tycho-2 catalogue and the Besançon Galaxy Model simulations, as well as our present our work on the model optimization.

For some time the Milky Way has been understood as a barred disk galaxy. Star count observations have provided evidence for two bars at apparently different orientations, the boxy bulge and a long planar bar. We report recent work in which we argued for a scenario where these observations can be reproduced with a single boxy bulge/bar: an evolved bar from the stellar disk and the corresponding boxy bulge generated from it through secular evolution and buckling instability. We calculated the star count distributions along different lines-of-sight for a simulated barred galaxy and an observer at the Sun position, and compared them with observations of red clump magnitude distributions. We found a good agreement between the model and the observations, even though the simulation has a single boxy bulge/bar. In this model, the different apparent orientations of the boxy bulge and planar bar are partially due to the volume effect and partially to the leading ends of the bar.

New data on the periods of Ap stars with references are presented. 161 further stars are introduced for which a periodic variability has recently been discovered or it was known before but it was not reported in previous issues of this catalogue. For many stars also present in previous issues of the catalogue new determinations of the periods are given. Recently attributed variable star names are also quoted.

Aims. We present CCD photometry in the Washington system C and T1 passbands down to T1 ∼ 22.5 in the fields of NGC 1697, SL 133, NGC 1997, SL 663, and OHSC 28, five mostly unstudied star clusters in the LMC. Methods. Cluster radii were estimated from star counts in appropriate-sized boxes distributed throughout the entire observed fields. We perform a detailed analysis of the field star contamination and derive cluster colour-magnitude diagrams (CMDs). Based on the best fits of isochrones computed by the Padova group to the (T1, C − T1) CMDs, the δ(T1) index and the Standard Giant Branch procedure, we derive metallicities and ages for the five clusters. We combine our sample with clusters with ages and metallicities on a similar scale and examine relationships between position in the LMC, age and metallicity. Results. With the exception of NGC 1697 (age = 0.7 Gyr, [Fe/H] = 0.0 dex), the remaining four clusters are of intermediate-age (from 2.2 to 3.0 Gyr) and relatively metal-poor ([Fe/H] = –0.7 dex). The cluster and field age-metallicty realtions show evidence for a metallicity offset but do overlap, particularly on the upper envelope side of the cluster age-metallicity relation. Conclusions. We confirm previous results that clusters younger than ∼1 Gyr were formed during an outside-in process; this occurred after a burst of cluster formation that took place mainly in the outer disk and peaked at ∼2 Gyr ago. Fil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina Fil: Geisler, D.. Universidad de Concepción; Chile Fil: Sarajedini, A.. University of Florida; Estados Unidos Fil: Gallart, C.. Instituto de Astrofísica de Canarias,; España

A database of published Stromgren four-color uvby photoelectric photometry for objects in the Stephenson-Sanduleak Luminous Stars in the Southern Milky Way catalog has been compiled from the literature. Of 5132 stars in the catalog, 817 have uvby colors and magnitudes available; altogether, the database incorporates 1181 observations from 41 references. The database is available electronically at CDS, and lists LS number, HD or CD number, , m 1 , c 1 , number of observations, numeric codes for notes and references, galactic and b coordinates, and aliases for named or variable stars.

We present the results of CCD BVI Johnson-Cousins photometry down to V = 19 mag in the regions of the unstudied stellar groups Pismis 23 and BH 222, both projected close to the direction to the Galactic centre. We measured V magnitudes and B-V and V-I colours for a total of 928 stars in fields of 4'x4'. Pismis 23 is conclusively a physical system, since a clear main sequence and other meaningful features can be seen in the colour-magnitude diagrams. The reality of this cluster is also supported by star counts carried out within and outside the cluster field. For Pismis 23 we derive colour excesses E(B-V) = 2.0 +/- 0.1 and E(V-I) = 2.6 +/- 0.1, a distance from the Sun of 2.6 +/- 0.6 kpc (Z = -0.19 pc) and an age of 300 +/- 100 Myr (assuming solar metal content). BH 222 appears to be a young open cluster formed by a vertical main sequence and by a conspicuous group of luminous, typically red supergiant stars. We derived for this cluster a colour excess E(V-I) = 2.4 +/- 0.2, a distance from the Sun of 6.0 +/- 0.7 kpc (Z = -0.46 pc) and an age of 60 +/- 30 Myr. The resulting reddening and distance estimates place these two young objects among the most reddened and distant open clusters known in the direction towards the Galactic centre. They are located beyond the Sagiattarius arm, close to the direction where this arm probably bifurcates into two arms. Fil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina Fil: Claria Olmedo, Juan Jose. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

We present CCD BVI observations obtained for 1759 stars in 4'x4' regions around the unstudied southern stellar aggregates Ruprecht 103, 124, 129, 146 and 166, which are described as open clusters in several catalogues. Our analysis shows that none of these stellar groups are genuine open clusters since no clear main sequences or meaningful features can be seen in their colour-magnitude diagrams. Star counts carried out within and outside the cluster candidate fields not only support these results but also show that the studied objects do not appear candidate late stages of star cluster dynamical evolution. Fil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina Fil: Claria Olmedo, Juan Jose. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Aims. To constrain the Initial Mass Function (IMF) of the Galactic young ( Methods. We have optimized the flexibility of the new Besancon Galaxy Model (Czekaj 2014) to simulate magnitude and distance complete samples of young intermediate mass stars assuming different IMFs and Star Formation Histories (SFH). Comparing the simulated synthetic catalogues with the observational data we studied which IMF reproduces better the observational number of Cepheids in the Galactic thin Disc. We analysed three different IMF: (1) Salpeter, (2) Kroupa-Haywood and (3) Haywood-Robin IMFs with a decreasing SFH from Aumer & Binney (2009). Results. For the first time the Besancon Galaxy Model is used to characterize the galactic Cepheids. We found that for most of the cases the Salpeter IMF overestimates the number of observed Cepheids and Haywood-Robin IMF underestimates it. The Kroupa-Haywood IMF, with a slope α = 3.2, is the one that best reproduces the observed Cepheids. From the comparison of the predicted and observed number of Cepheids up to V = 12, we point that the model might underestimate the scale height of the young population. Conclusions. In agreement with Kroupa & Weidner (2003) our study shows that the Salpeter IMF (α = 2.35) overestimates the star counts in the range 4 ≤ M / M ⊙ ≤ 10 and supports the idea that the slope of the intermediate and massive stars IMF is steeper than the Salpeter IMF. The poster can be found online at: https://gaia.ub.edu/Twiki/pub/GREATITNFC/ProgramFinalconference/Poster_R._Mor_Great.pdf .

Context. High-velocity halo stars provide important information about the properties of the extreme Galactic halo. The study of Population II unbound and bound stars enables us better estimate the mass of the halo. Aims. We carried out a detailed spectroscopic and kinematic study of two red horizontal branch stars, CD-41 15048 and HD 214362. Methods. The atmospheric parameters, chemical abundances, and kinematical properties were determined using high-resolution optical spectroscopy and employing the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code moog. Results. We found that CD-41 15048 and HD 214362 are metal-poor red horizontal branch stars. Their abundance patterns are similar to other metal-poor halo stars already investigated. Our kinematic analysis of the 3D space motions shows that HD 214362 has a highly eccentric (e = 0:95) orbit and passes at 2 kpc from the Galactic center. CD-41 15048, for an adopted distance of 1.3 kpc, has an extreme retrograde motion and travels with very high velocity relative to the Galactocentric reference frame (VGRF = 583 km s 1 ). Conclusions. CD-41 15048 is a bound or an unbound star, depending on the adopted Galactic potential. We also show that the red horizontal branch star BD+09 3223 is another example of a hypervelocity star. Whether it is bound or unbound to the Galaxy depends on the assumed mass and adopted Galactic potential. Possible origins of these two high-velocity stars are briefly discussed. CD-41 15048 and BD+09 3223 are further examples of evolved stars to join the restricted group of hypervelocity stars. Finally, our results seem to contradict the idea that a passage of a star very close to the Galactic center is the only possible origin of hypervelocity stars.

To enlarge our growing sample of well-studied star clusters in the Large Magellanic Cloud (LMC), we present CCD Washington CT1 photometry to T1 ~ 23 in the fields of twenty-three mostly unstudied clusters located in the inner disc and outer regions of the LMC. We estimated cluster radii from star counts. Using the cluster Washington (T1,C-T1) colour-magnitude diagrams, statistically cleaned from field star contamination, we derived cluster ages and metallicities from a comparison with theoretical isochrones of the Padova group. Whenever possible, we also derived ages using delta_T1 - the magnitude difference between the red giant clump and the main sequence turn off - and estimated metallicities from the standard giant branch procedure. We enlarged our sample by adding clusters with published ages and metallicities determined on a similar scale by applying the same methods. We examined relationships between their positions in the LMC, ages and metallicities. We find that the two methods for age and metallicity determination agree well with each other. Fourteen clusters are found to be intermediate-age clusters (1-2 Gyr), with [Fe/H] values ranging from -0.4 to -0.7. The remaining nine clusters turn out to be younger than 1 Gyr, with metallicities between 0.0 and -0.4. Our 23 clusters represent an increase of ~ 30% in the current total amount number of well-studied LMC clusters using Washington photometry. In agreement with previous studies, we find no evidence for a metallicity gradient. We also find that the younger clusters were formed closer to the LMC centre than the older ones., Comment: 11 pages, 10 figures. A&A, in press

International audience; Faint high-latitude carbon stars (FHLCs) are distant, luminous giants. For this reason, they are often used to study the dynamical and chemical properties of the Galactic Halo. However, a more accurate investigation of photometric and spectroscopic surveys has revealed an increasing number of such objects with luminosities of main sequence stars. We report the first results of a systematic search of FHLCs using the Digitized First Byurakan Survey (DFBS) low-resolution spectral database. The DFBS low-resolution spectral plates are analysed to find new faint early and late-type carbon star candidates. Twenty new faint high-latitude carbon star candidates have been detected in an area of ∼4030 sq. deg. Moderate-resolution slit spectroscopy was carried out for all candidates, confirming the carbon star nature for thirteen of them (nine are new discoveries), while the remaining objects are M-type stars. The carbon star sample consists of five N-type carbon stars, for which the estimated mass-loss rates agree well with the typical ones found for such carbon stars; five comparatively bright CH-type carbon stars; and three are probably dwarf carbon (dC) stars. The distance determination indicates that the dwarf carbon stars belong to the thin disk, while the other stars belong the Galactic halo. These results demonstrate that one can efficiently find new faint high-latitude carbon star in the Digitized First Byurakan Survey database.

Aims. We use the surface brightness fluctuation (SBF) technique to derive the distances and analyse the radial behaviour of stellar populations in a sample of 12 elliptical galaxies. The data are I-band images collected with the FORS1 camera at the Very Large Telescope (VLT), drawn from the ESO archive. The main purpose of our analysis is to carry out the study of SBF magnitudes without relying on additional colour information that is normally required in SBF studies. Methods. We measure I-band SBF magnitudes and SBF variations with galaxy radii, which is useful for stellar population studies. Unlike typical applications of the SBF technique, the absolute SBF magnitudes needed to evaluate the distance moduli are derived using the fluctuation star count, ¯ N. Results. The distances obtained using the ¯ N calibration taken from the literature show a good agreement with available estimates. We find a median ∼0.2 mag difference between our and literature distance moduli, with the only exception of NGC 5090, which shows the I-band SBF ∼1 mag brighter than expected. The median statistical and systematic errors are ∼0.2 and ∼0.1 mag, respectively. On these grounds we consider the test of deriving SBF distances based on the ¯ N calibration to be successful. Taking into account that some of the previously estimated distances were made as long as 15 years ago, the new measurements provide an updated sketch on distances for a set of galaxies towards the region of the Great Attractor. Furthermore, gauging the SBF of the unresolved stellar systems has returned negative SBF radial gradients in the inner regions of five galaxies: a feature already known and explained by lower metallicity at larger galactic radii. Somehow unexpectedly, though, we detect positive SBF gradients at large radii (>20 kpc) in nine targets. This behaviour, if it is not caused by some unaccounted observational bias, could be explained at least partly as a statistical effect on the stellar counts at these radii. Additional (near-IR) observations are necessary to confirm the real existence of this feature and to allow us to reach more robust conclusions.

We present a detailed study of the dwarf galaxy VV124, recently recognized as a isolated member of the Local Group. We have obtained deep (r=26.5) wide-field g,r photometry of individual stars with the LBT under sub-arcsec seeing conditions. The Color-Magnitude Diagram suggests that the stellar content of the galaxy is dominated by an old, metal-poor population, with a significant metallicity spread. A very clean detection of the RGB tip allows us to derive an accurate distance of D=1.3 +/- 0.1 Mpc. Combining surface photometry with star counts, we are able to trace the surface brightness profile of VV124 out to ~ 5' = 1.9 kpc radius (where mu_r=30 mag/arcsec^2), showing that it is much more extended than previously believed. Moreover, the surface density map reveals the presence of two symmetric flattened wings emanating from the central elongated spheroid and aligned with its major axis, resembling a stellar disk seen nearly edge-on. We also present HI observations obtained with the WSRT, the first ever of this object. A total amount of 10^6 M_sun of HI gas is detected in VV124. Compared to the total luminosity, this gives a value of M_HI/L_V=0.11, which is particularly low for isolated Local Group dwarfs. The spatial distribution of the gas does not correlate with the observed stellar wings. The systemic velocity of the HI in the region superposed to the stellar main body of the galaxy is V_h=-25 km/s. The velocity field shows substructures typical of galaxies of this size but no sign of rotation. The HI spectra indicates the presence of a two-phase interstellar medium, again typical of many dwarf galaxies., Comment: Accepted for publication in A&A. 19 pages, 20 reduced-resolution figures, pdflatex, A&A style. The full resolution pdf file can be be downloaded from http://www.bo.astro.it/SGR/

The \Catalogue of Stars in the Northern Milky Way Having H-alpha in Emission" appears in Abhandlungen aus der Hamburger Sternwarte, Band XI in the year 1997. It contains 4174 stars, range 32 l II < 214; 10

We present an extinction map of the Polaris molecular cirrus cloud derived from star counts and compare it with the Schlegel et al. [13] extinction map derived from the far-infrared dust opacity. We find that, within the Polaris cloud, the Schlegel et al. [13] AV values are, on average, a factor 2 higher than the star count values. We propose that this discrepancy results from a difference in τFIR/AV between the diffuse atomic medium and the Polaris cloud. We use the difference in spectral energy distribution, warm for the diffuse atomic medium, cold for the Polaris cloud, to separate their respective contribution to the line of sight integrated infrared emission and find that the τFIR/AV of cold dust in Polaris is on average 4 times higher than the Schlegel et al. [13] value for dust in atomic cirrus. This change in dust property could be interpreted by a growth of fluffy particles within low opacity molecular cirrus clouds such as Polaris. Our work suggests that variations in dust emissivity must be taken into account to estimate AV from dust emission wherever cold infrared emission is present (i.e. molecular clouds).