Browsing by Author "Surot, F."

Now showing 1 - 10 of 10
  • No Thumbnail Available
    Item
    A new distance to the Brick, the dense molecular cloud G0.253+0.016
    (2021) Zoccali, M.; Valenti, E.; Surot, F.; Gonzalez, O. A.; Renzini, A.; Valenzuela Navarro, A.
    We analyse the near-infrared colour-magnitude diagram of a field including the giant molecular cloud G0.253+0.016 (a.k.a. The Brick) observed at high spatial resolution, with HAWK-I@VLT. The distribution of red clump stars in a line of sight crossing the cloud, compared with that in a direction just beside it, and not crossing it, allow us to measure the distance of the cloud from the Sun to be 7.20, with a statistical uncertainty of +/- 0.16 and a systematic error of +/- 0.20 kpc. This is significantly closer than what is generally assumed, i.e. that the cloud belongs to the near side of the central molecular zone, at 60 pc from the Galactic centre. This assumption was based on dynamical models of the central molecular zone, observationally constrained uniquely by the radial velocity of this and other clouds. Determining the true position of the Brick cloud is relevant because this is the densest cloud of the Galaxy not showing any ongoing star formation. This puts the cloud off by one order of magnitude from the Kennicutt-Schmidt relation between the density of the dense gas and the star formation rate. Several explanations have been proposed for this absence of star formation, most of them based on the dynamical evolution of this and other clouds, within the Galactic centre region. Our result emphasizes the need to include constraints coming from stellar observations in the interpretation of our Galaxy's central molecular zone.
  • Thumbnail Image
    Item
    Galactic bulge population II Cepheids in the VVV survey: period-luminosity relations and a distance to the Galactic centre
    (2017) Bhardwaj, A.; Rejkuba, M.; Minniti, D.; Surot, F.; Valenti, E.; Zoccali, Manuela; Gonzalez, O.; Romaniello, M.; Kanbur, S.; Singh, H.
  • Thumbnail Image
    Item
    M dwarfs in the b201 tile of the VVV survey : Colour-based selection, spectral types and light curves
    (2014) Rojas-Ayala, B.; Iglesias, D.; Minniti, D.; Saito, R.; Surot, F.
  • Thumbnail Image
    Item
    Mapping the stellar age of the Milky Way bulge with the VVV I. The method
    (2019) Surot, F.; Valenti, E.; Hidalgo, S.L.; Zoccali, Manuela; Sokmen, E.; Rejkuba, M.; Minniti, D.; Gonzalez, O.A.; Cassisi, S.; Renzini, O.; Weiss, A.
  • No Thumbnail Available
    Item
    Mapping the stellar age of the Milky Way bulge with the VVV II. Deep JKs catalog release based on PSF photometry
    (2019) Surot, F.; Valenti, E.; Hidalgo, S. L.; Zoccali, M.; Gonzalez, O. A.; Sokmen, E.; Minniti, D.; Rejkuba, M.; Lucas, P. W.
    Context. The bulge represents the best compromise between old and massive Galactic components, and as such its study is a valuable opportunity to understand how the bulk of the Milky Way formed and evolved. In addition, being the only bulge in which we can individually resolve stars in all evolutionary sequences, the properties of its stellar content provide crucial insights into the formation of bulges.
  • No Thumbnail Available
    Item
    Mapping the stellar age of the Milky Way bulge with the VVV III. High-resolution reddening map
    (2020) Surot, F.; Valenti, E.; Gonzalez, O. A.; Zoccali, M.; Sokmen, E.; Hidalgo, S. L.; Minniti, D.
    Context. A detailed study of the Galactic bulge stellar population necessarily requires an accurate representation of the interstellar extinction, particularly toward the Galactic plane and center, where severe and differential reddening is expected to vary on sub-arcmin scales. Although recent infrared surveys have addressed this problem by providing extinction maps across the whole Galactic bulge area, dereddened color-magnitude diagrams near the plane and center appear systematically undercorrected, prompting the need for higher resolution. These undercorrections affect any stellar study sensitive to color (e.g., star formation history analyses via color-magnitude diagram fitting), either making them inaccurate or limiting them to small and relatively stable extinction windows where this value is low and better constrained.Aims. This study is aimed at providing a high-resolution (2 arcmin to similar to 10 arcsec) color excess map for the VVV bulge area in J-K-s color.Methods. We used the MW-BULGE-PSFPHOT catalogs, sampling similar to 300 deg(2) across the Galactic bulge (|l| < 10 degrees and -10 degrees< b< 5 degrees) to isolate a sample of red clump and red giant branch stars, for which we calculated the average J-K-s color in a fine spatial grid in (l, b) space.Results. We obtained an E(J-K-s) map spanning the VVV bulge area of roughly 300 deg(2), with the equivalent of a resolution between similar to 1 arcmin for bulge outskirts (l< 6 degrees) to below 20 arcsec within the central |l| < 1 degrees, and below 10 arcsec for the innermost area (|l| < 1 degrees and |b| < 3 degrees).
  • Thumbnail Image
    Item
    New variable stars towards the Galactic Bulge - I. The bright regime
    (2019) Kains, N.; Calamida, A.; Rejkuba, M.; Bhardwaj, A.; Inno, L.; Sahu, K.C.; Zoccali, Manuela; Bono, G.; Surot, F.; Anderson, J.; Casertano, S.
  • Thumbnail Image
    Item
    The central velocity dispersion of the milky way bulge
    (2018) Valenti, E.; Zoccali, Manuela; Mucciarelli, A.; Gonzalez, O.A.; Surot, F.; Minniti, D.; Rejkuba, M.; Pasquini, L.; Fiorentino, G.; Bono, G.; Rich, R.M.; Soto, M.
  • Thumbnail Image
    Item
    The diffuse interstellar band around 8620 Å : I. Methods and application to the GIBS data set
    (2021) Zhao, H.; Schultheis, M.; Recio-Blanco, A.; Kordopatis, G.; De Laverny, P.; Rojas Arriagada, Alvaro; Zoccali, Manuela; Surot, F.; Valenti, E.
  • No Thumbnail Available
    Item
    The diffuse interstellar band around 8620 Å II. Kinematics and distance of the DIB carrier
    (2021) Zhao, H.; Schultheis, M.; Rojas-Arriagada, A.; Recio-Blanco, A.; de Laverny, P.; Kordopatis, G.; Surot, F.
    Context. Diffuse interstellar bands (DIBs) are important interstellar absorption features of which the origin is still debated. With the large data sets from modern spectroscopic surveys, background stars are widely used to show how the integrated columns of DIB carriers accumulate from the Sun to great distances. To date, studies on the kinematics of the DIB carriers are still rare. Aims. We aim to make use of the measurements from the Giraffe Inner Bulge Survey (GIBS) and the Gaia-ESO survey (GES) to study the kinematics and distance of the carrier of DIB lambda 8620, as well as other properties. Methods. The DIBs were detected and measured following the same procedures as in Zhao et al. (2021, A&A, 645, A14; hereafter Paper I), assuming a Gaussian profile. The median radial velocities of the DIB carriers in 38 GIBS and GES fields were used to trace their kinematics, and the median distances of the carriers in each field were estimated by the median radial velocities and two applied Galactic rotation models. Results. We successfully detected and measured DIB lambda 8620 in 760 of 4117 GES spectra with |b| <= 10 degrees and signal-to-noise ratio (S/N) > 50. Combined with the DIBs measured in GIBS spectra (Paper I), we confirmed a tight relation between EW and E(J - K-S) as well as A(V), with similar fitting coefficients to those found by previous works. With a more accurate sample and the consideration of the solar motion, the rest-frame wavelength of DIB lambda 8620 was redetermined as 8620.83 A, with a mean fit error of 0.36 A. We studied the kinematics of the DIB carriers by tracing their median radial velocities in each field in the local standard of rest (V-LSR) and into the galactocentric frame (V-GC), respectively, as a function of the Galactic longitudes. Based on the median V-LSR and two Galactic rotation models, we obtained valid kinematic distances of the DIB carriers for nine GIBS and ten GES fields. We also found a linear relation between the DIB lambda 8620 measured in this work and the near-infrared DIB in APOGEE spectra at 1.5273 mu m, and we estimated the carrier abundance to be slightly lower compared to the DIB lambda 15273. Conclusions. We demonstrate that the DIB carriers can be located much closer to the observer than the background stars based on the following arguments: (i) qualitatively, the carriers occupy in the Galactic longitude-velocity diagram typical rotation velocities of stars in the local Galactic disk, while the background stars in the GIBS survey are mainly located in the Galactic bulge; (ii) quantitatively, all the derived kinematic distances of the DIB carriers are smaller than the median distances to background stars in each field. A linear correlation between DIB lambda 8620 and DIB lambda 15273 has been established, showing similar carrier abundances and making them both attractive for future studies of the interstellar environments.