Examinando por Autor "Majaess, D."
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Ítem A colour-excess extinction map of the southern Galactic disc from the VVV and GLIMPSE surveys(Monthly Notices of the Royal Astronomical Society, 2019-09-11) Soto, M.; Barba, R.; Minniti, D.; Kunder, A.; Majaess, D.; Nilo-Castellon, J. L.; Alonso-García, J.; Leone, G.; Morelli, L.; Haikala, L.; Firpo, V.; Lucas, P.; Emerson, J. P.; Moni Bidin, C.; Geisler, D.; Saito, R. K.; Gurovich, S.; Contreras Ramos, R.; Rejkuba, M.; Barbieri, M.; Roman-Lopes, A.; Hempel, M.; Alonso, M. V.; Baravalle, L. D.; Borissova, J.; Kurtev, R.; Milla, F.An improved high-resolution and deep AKs foreground dust extinction map is presented for the Galactic disc area within 295◦ ≾ l ≾ 350◦, −1.0◦ ≾ b ≾ +1.0◦. At some longitudes the map reaches up to |b| ~ 2.25◦, for a total of ~148 deg2. The map was constructed via the Rayleigh–Jeans colour excess (RJCE) technique based on deep near-infrared (NIR) and mid-infrared (MIR) photometry. The new extinction map features a maximum bin size of 1 arcmin, and relies on NIR observations from the Two Micron All-Sky Survey (2MASS) and new data from ESO’s Vista Variables in the Vía Láctea (VVV) survey, in concert with MIR observations from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire. The VVV photometry penetrates ~4 mag fainter than 2MASS, and provides enhanced sampling of the underlying stellar populations in this heavily obscured region. Consequently, the new results supersede existing RJCE maps tied solely to brighter photometry, revealing a systematic underestimation of extinction in prior work that was based on shallower data. The new high-resolution and large-scale extinction map presented here is readily available to the community through a web query interface.Ítem A new near-IR window of low extinction in the Galactic plane(EDP Sciences, 2018-08) Minniti, D.; Saito, R.K.; Gonzalez, O.A.; Alonso-García, J.; Rejkuba, M.; Barbá, R.; Irwin, M.; Kammers, R.; Lucas, P.W.; Majaess, D.; Valenti, E.Aims. The windows of low extinction in the Milky Way (MW) plane are rare but important because they enable us to place structural constraints on the opposite side of the Galaxy, which has hither to been done rarely. Methods. We use the near-infrared (near-IR) images of the VISTA Variables in the Vía Láctea (VVV) Survey to build extinction maps and to identify low extinction windows towards the Southern Galactic plane. Here we report the discovery of VVV WIN 1713-3939, a very interesting window with relatively uniform and low extinction conveniently placed very close to the Galactic plane. Results. The new window of roughly 30 arcmin diameter is located at Galactic coordinates (l, b) = (347.4, -0.4) deg. We analyse the VVV near-IR colour-magnitude diagrams in this window. The mean total near-IR extinction and reddening values measured for this window are A Ks = 0.46 and E(J - K s ) = 0.95. The red clump giants within the window show a bimodal magnitude distribution in the K s band, with peaks at K s = 14.1 and 14.8 mag, corresponding to mean distances of D = 11.0 ± 2.4 and 14.8 ± 3.6 kpc, respectively. We discuss the origin of these red clump overdensities within the context of the MW disk structure. © ESO 2018.Ítem Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane(IOP PUBLISHING, 2017-03) Minniti, D.; Dékány, I.; Majaess, D.; Palma, T.; Pullen, J.; Rejkuba, M.; Alonso-García, J.; Catelan, M.; Contreras Ramos, R.; Gonzalez, O.A.; Hempel, M.; Irwin, M.l; Lucas, P.W.; Saito, R.K.; Tissera, P.; Valenti, E.; Zoccali, M.Deep near-IR images from the VISTA Variables in the Via Lactea (VVV) Survey were used to search for RR Lyrae stars in the Southern Galactic plane. A sizable sample of 404 RR Lyrae of type ab stars was identified across a thin slice of the fourth Galactic quadrant (295 degrees < l < 350 degrees, -2 degrees.24 < b < -1 degrees.05). The sample's distance distribution exhibits a maximum density that occurs at the bulge tangent point, which implies that this primarily Oosterhoff type I population of RRab stars does not trace the bar delineated by their red clump counterparts. The bulge RR Lyrae population does not extend beyond l similar to 340 degrees, and the sample's spatial distribution presents evidence of density enhancements and substructure that warrants further investigation. Indeed, the sample may be employed to evaluate Galactic evolution models, and is particularly lucrative since half of the discovered RR Lyrae are within reach of Gaia astrometric observations.Ítem Discovery of a pair of classical cepheids in an invisible cluster beyond the galactic bulge(Institute of Physics Publishing, 2015-01) Dékány, I.; Minniti, D.; Alonso-García, J.; Hempel, M.; Palma, T.; Catelan, M.; Gieren, W.; Majaess, D.We report the discovery of a pair of extremely reddened classical Cepheid variable stars located in the Galacticplane behind the bulge, using near-infrared (NIR) time-series photometry from the VISTA Variables in the VaLáctea Survey. This is the first time that such objects have ever been found in the opposite side of the Galacticplane. The Cepheids have almost identical periods, apparent brightnesses, and colors. From the NIR Leavitt law,we determine their distances with ∼1.5% precision and ∼8% accuracy. We find that they have a same totalextinction of A(V) ? 32 mag, and are located at the same heliocentric distance of ádn = 11.4 ± 0.9 kpc, and lessthan 1 pc from the true Galactic plane. Their similar periods indicate that the Cepheids are also coeval, with an ageof ∼48 ± 3Myr, according to theoretical models. They are separated by an angular distance of only 18?.3,corresponding to a projected separation of ∼1 pc. Their position coincides with the expected location of the Far 3kpc Arm behind the bulge. Such a tight pair of similar classical Cepheids indicates the presence of an underlyingyoung open cluster that is both hidden behind heavy extinction and disguised by the dense stellar field of the bulge.All our attempts to directly detect this invisible cluster have failed, and deeper observations are needed.Ítem The Emergence of the Infrared Transient VVV-WIT-06(Institute of Physics Publishing, 2017-11) Minniti, D.; Saito, R.K.; Forster, F.; Pignata, G.; Ivanov, V.D.; Lucas, P.W.; Beamin, J.C.; Borissova, J.; Catelan, M.; Gonzalez, O.A.; Hempel, M.; Hsiao, E.; Kurtev, R.; Majaess, D.; Masetti, N.; Morrell, N.I.; Phillips, M.M.; Pullen, J.B.; Rejkuba, M.; Smith, L.; Surot, F.; Valenti, E.; Zoccali, M.We report the discovery of an enigmatic large-amplitude (ΔKs >10.5 mag) transient event in near-IR data obtained by the VISTA Variables in the Via Lactea (VVV) ESO Public Survey. The object (designated VVV-WIT- 06) is located at R.A.=17:07:18.917, decl.=-39:06:26.45 (J2000), corresponding to Galactic coordinates l=347.14539, b=0.88522. It exhibits a clear eruption, peaking at Ks=9 mag during 2013 July and fading to Ks ∼ 16.5 in 2017. Our late near-IR spectra show post-outburst emission lines, including some broad emission lines (upward of FWHM ∼ 3000 km s-1). We estimate a total extinction of AV = 10-15 mag in the surrounding field, and no progenitor was observed in ZYJHKs images obtained during 2010-2012 (down to Ks > 18.5mag). Subsequent deep near-IR imaging and spectroscopy, in concert with the available multiband photometry, indicate that VVV-WIT-06 may be either: (i) the closest Type I SN observed in about 400 years, (ii) an exotic highamplitude nova that would extend the known realm of such objects, or (iii) a stellar merger. In all of these cases, VVV-WIT-06 is a fascinating and curious astrophysical target under any of the scenarios considered.Ítem THE VVV SURVEY REVEALS CLASSICAL CEPHEIDS TRACING A YOUNG and THIN STELLAR DISK ACROSS the GALAXY'S BULGE(Institute of Physics Publishing, 2015-10) Dékány, I.; Minniti, D.; Majaess, D.; Zoccali, M.; Hajdu, G.; Alonso-García, J.; Catelan, M.; Gieren, W.; Borissova, J.Solid insight into the physics of the inner Milky Way is key to understanding our Galaxy's evolution, but extreme dust obscuration has historically hindered efforts to map the area along the Galactic mid-plane. New comprehensive near-infrared time-series photometry from the VVV Survey has revealed 35 classical Cepheids, tracing a previously unobserved component of the inner Galaxy, namely a ubiquitous inner thin disk of young stars along the Galactic mid-plane, traversing across the bulge. The discovered period (age) spread of these classical Cepheids implies a continuous supply of newly formed stars in the central region of the Galaxy over the last 100 million years. © 2015. The American Astronomical Society. All rights reserved.