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Sanchez S.F.,Centro Astronomico Hispano Aleman | Rosales-Ortega F.F.,University of Cambridge | Kennicutt R.C.,University of Cambridge | Johnson B.D.,University of Cambridge | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2011

We present a wide-field Integral Field Spectroscopy (IFS) survey on the nearby face-on Sbc galaxy NGC 628, comprising 11094 individual spectra, covering a nearly circular field-of-view of ~6 arcmin in diameter, with a sampling of ~2.7 arcsec per spectrum in the optical wavelength range (3700-7000 Å). This galaxy is part of the PPAK IFS Nearby Galaxies Survey (PINGS). To our knowledge, this is the widest spectroscopic survey ever made in a single nearby galaxy. A detailed flux calibration was applied, granting a spectrophotometric accuracy of ~0.2 mag. The spectroscopic data were analysed both as a single integrated spectrum that characterizes the global properties of the galaxy and using each individual spectrum to determine the spatial variation of the stellar and ionized gas components. The spatial distribution of the luminosity-weighted ages and metallicities of the stellar populations was analysed. Using typical strong emission-line ratios we derived the integrated and 2D spatial distribution of the ionized gas, the dust content, star formation rate (SFR) and oxygen abundance.The age of the stellar populations shows a negative gradient from the inner (older) to the outer (younger) regions. We found an inversion of this gradient in the central ~1 kpc region, where a somewhat younger stellar population is present within a ring at this radius. This structure is associated with a circumnuclear star-forming region at ~500 pc, also found in similar spiral galaxies. From the study of the integrated and spatially resolved ionized gas, we found a moderate SFR of ~2.4 M07dot; yr-1. The oxygen abundance shows a clear gradient of higher metallicity values from the inner part to the outer part of the galaxy, with a mean value of 12 + log(O/H) ~ 8.7. At some specific regions of the galaxy, the spatially resolved distribution of the physical properties shows some level of structure, suggesting real point-to-point variations within an individual H ii region. Our results are consistent with an inside-out growth scheme, with stronger star formation at the outer regions, and with evolved stellar populations in the inner ones. © 2010 The Authors. Journal compilation © 2010 RAS.

Rosales-Ortega F.F.,University of Cambridge | Kennicutt R.C.,University of Cambridge | Sanchez S.F.,Centro Astronomico Hispano Aleman | Diaz A.I.,Autonomous University of Madrid | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2010

We present the PPAK Integral Field Spectroscopy (IFS) Nearby Galaxies Survey (PINGS), a two-dimensional spectroscopic mosaicking of 17 nearby disc galaxies in the opticalwavelength range. This project represents the first attempt to obtain continuous coverage spectra of the whole surface of a galaxy in the nearby Universe. The final data set comprises more than 50 000 individual spectra, covering in total an observed area of nearly 80 arcmin2. The observations will be supplemented with broad-band and narrow-band imaging for those objects without publicly available images in order to maximize the scientific and archival values of the data set. In this paper we describe the main astrophysical issues to be addressed by the PINGS project, present the galaxy sample and explain the observing strategy, the data reduction process and all uncertainties involved. Additionally, we give some scientific highlights extracted from the first analysis of the PINGS sample. A companion paper will report on the first results obtained for NGC 628: the largest IFS survey on a single galaxy. © 2010 The Authors. Journal compilation © 2010 RAS.

Covey K.R.,Harvard - Smithsonian Center for Astrophysics | Covey K.R.,Cornell University | Lada C.J.,Harvard - Smithsonian Center for Astrophysics | Roman-Zuniga C.,Centro Astronomico Hispano Aleman | And 4 more authors.
Astrophysical Journal | Year: 2010

We have investigated the stellar content of Barnard 59 (B59), the most active star-forming core in the Pipe Nebula. Using the SpeX spectrograph on the NASA Infrared Telescope Facility, we obtained moderate resolution, nearinfrared (NIR) spectra for 20 candidate young stellar objects (YSOs) in B59 and a representative sample of NIR and mid-IR bright sources distributed throughout the Pipe. Measuring luminosity and temperature sensitive features in these spectra, we identified likely background giant stars and measured each star's spectral type, extinction, and NIR continuum excess. To measure B59's age, we place its candidate YSOs in the Hertzsprung-Russell diagram and compare their location to YSOs in several well-studied star-forming regions, as well as predictions of pre-main-sequence (PMS) evolutionary models. We find that B59 is composed of late-type (K4-M6) low-mass (0.9-0.1 M⊙) YSOs whose median stellar age is comparable to, if not slightly older than, that of YSOs within the ρ Oph, Taurus, and Chameleon star-forming regions. Deriving absolute age estimates from PMS models computed by D'Antona et al., and accounting only for statistical uncertainties, we measure B59's median stellar age to be 2.6 ± 0.8 Myr. Including potential systematic effects increases the error budget for B59's median (DM98) stellar age to 2.6+4.1 -2.6 Myr. We also find that the relative age orderings implied by PMS evolutionary tracks depend on the range of stellar masses sampled, as model isochrones possess significantly different mass dependences. The maximum likelihood median stellar age we measure for B59, and the region's observed gas properties, suggests that the B59 dense core has been stable against global collapse for roughly six dynamical timescales and is actively forming stars with a star formation efficiency per dynamical time of ∼6%. While the ∼150% uncertainties associated with our age measurement propagate directly into these derived star formation timescales, the maximum likelihood values nonetheless agree well with recent star formation simulations that incorporate various forms of support against collapse, such as subcritical magnetic fields, outflows, and radiative feedback from protostellar heating. Copyright is not claimed for this article. All rights reserved. Printed in the U.S.A.

Miralles-Caballero D.,Autonomous University of Madrid | Diaz A.I.,Autonomous University of Madrid | Rosales-Ortega F.F.,National Institute of Astrophysics, Optics and Electronics | Perez-Montero E.,Institute Astrofisica Of Andalucia | And 2 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

Numerical simulations of minor mergers predict little enhancement in the global star formation activity. However, it is still unclear the impact they have on the chemical state of the whole galaxy and on the mass build-up in the galaxy bulge and disc. We present a two-dimensional analysis of NCG 3310, currently undergoing an intense starburst likely caused by a recent minor interaction, using data from the PPAK Integral Field Spectroscopy Nearby Galaxies Survey (PINGS). With data from a large sample of about a hundred HII regions identified throughout the disc and spiral arms, we derive, using strong-line metallicity indicators and direct derivations, a rather flat gaseous abundance gradient. Thus, metal mixing processes occurred, as in observed galaxy interactions. Spectra from PINGS data and additional multiwavelength imaging were used to perform a spectral energy distribution fitting to the stellar emission and a photoionization modelling of the nebulae. The ionizing stellar population is characterized by single populations with a narrow age range (2.5-5 Myr) and a broad range of masses (104-6 × 106 M Ȯ). The effect of dust grains in the nebulae is important, indicating that 25-70 per cent of the ultraviolet photons can be absorbed by dust. The ionizing stellar population within the HII regions represents typically a few per cent of the total stellar mass. This ratio, a proxy to the specific star formation rate, presents a flat or negative radial gradient. Therefore, minor interactions may indeed play an important role in the mass build-up of the bulge. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Chilingarian I.V.,University of Strasbourg | Chilingarian I.V.,Moscow State University | Bergond G.,Centro Astronomico Hispano Aleman | Bergond G.,Institute Astrofisica Of Andalucia Csic
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2010

We report the discovery of the second compact elliptical (cE) galaxy SDSS J150634.27 + 013331.6 in the nearby NGC 5846 group by the Virtual Observatory (VO) workflow. This object (M B = -15.98 mag, R e = 0.24 kpc) becomes the fifth cE where the spatially resolved kinematics and stellar populations can be obtained. We used archival HST WFPC2 images to demonstrate that its light profile has a two-component structure, and integrated photometry from GALEX, SDSS, UKIDSS and Spitzer to build the multiwavelength spectral energy distribution to constrain the star formation history (SFH). We observed this galaxy with the PMASIFU spectrograph at the Calar-Alto 3.5-m telescope and obtained two-dimensional maps of its kinematics and stellar population properties using the full-spectral fitting technique. Its structural, dynamical and stellar population properties suggest that it had a massive progenitor heavily tidally stripped by NGC 5846. © 2010 The Authors. Journal compilation © 2010 RAS.

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