Asociacion ASPID

La Laguna, Spain

Asociacion ASPID

La Laguna, Spain
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Oteo I.,Institute of Astrophysics of Canarias | Oteo I.,University of La Laguna | Bongiovanni A.,Institute of Astrophysics of Canarias | Bongiovanni A.,University of La Laguna | And 12 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

We analyse the rest-frame ultraviolet (UV) to near-infrared (near-IR) spectral energy distribution (SED) of Lyman-break galaxies (LBGs), star-forming (SF) BzK (sBzK) and UV-selected galaxies at 1.5 ≳ z ≳ 2.5 in the COSMOS, GOODS-N and GOODS-S fields. Additionally, we complement the multiwavelength coverage of the galaxies located in the GOODS fields with deep far-infrared (FIR) data taken from the GOODS-Herschel project. According to their best-fitting SED-derived properties we find that, because of their selection criterion involving UV measurements, LBGs tend to be UV-brighter and bluer and have a less prominent Balmer break (i.e. are younger) and higher dust-corrected total star-formation rate (SFR) than sBzK galaxies. In this way, sBzK galaxies represent the general population of SF galaxies at z ̃ 2 better than LBGs. In a colour-mass diagram, LBGs at z ̃ 2 are mostly located over the blue cloud, although galaxies with higher age, higher dust attenuation and redder UV continuum slope deviate to the green valley and red sequence. Furthermore, for a given stellar mass, LBGs tend to have bluer optical colours than sBzK and UV-selected galaxies. We find clean Photodetector Array Camera and Spectrometer (PACS: 100-or 160-μm) individual detections for a subsample of 48 LBGs, 89 sBzK and 91 UV-selected galaxies that measure their dust emission directly. Their SFRtotal = SFRUV + SFRIR cannot be recovered with the dust-correction factors derived from their continuum slope and the infrared excess (IRX)-β relations for local starbursts, similar to what happens at higher redshifts. This might have implications, for example, in the definition of the main sequence (MS) at z ̃ 2, which is sensitive to the dust-correction factors adopted. In an SFR-mass diagram, PACS-detected galaxies are located above the Daddi et al. MS and thus their star formation is probably driven by starbursts. This is in agreement with the shape of their IR SEDs. PACS-detected galaxies with redder UV continuum slope and higher stellar mass are more attenuated. We find that, for a given UV continuum slope, the dustiest galaxies at higher redshifts are more attenuated and that for a given stellar mass the dustiest galaxies at higher redshifts have stronger FIR emission. This suggests an evolution of their dust properties. However, we do not find significant evolution in the relation between dust attenuation and stellar mass with redshift, at least at z ≤ 2.5. There is a subpopulation of 17, 26 and 27 LBGs, sBzK and UV-selected galaxies, respectively, that are detected in any of the Spectral and Photometric Imaging REceiver (SPIRE: 250-, 350-and 500-μm) bands. We speculate that this sample of SPIRE-detected LBGs is the bridging population between submillimetre galaxies and LBGs. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.


Oteo I.,Institute of Astrophysics of Canarias | Oteo I.,University of La Laguna | Bongiovanni A.,Institute of Astrophysics of Canarias | Bongiovanni A.,University of La Laguna | And 37 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

We take advantage of the exceptional photometric coverage provided by the combination of GALEX data in the ultraviolet (UV) and the ALHAMBRA survey in the optical and near-infrared to analyse the physical properties of a sample of 1225 GALEX-selected Lyman break galaxies (LBGs) at 0.8 ≲ z ≲ 1.2 that are located in the COSMOS field. This is the largest sample of LBGs studied in this redshift range to date. According to a spectral energy distribution (SED) fitting with synthetic stellar population templates, we find that LBGs at z ̃ 1 are mostly young galaxies with a median age of 341 Myr and have intermediate dust attenuation, (Es(B - V)) ̃ 0.20. Owing to the selection criterion, LBGs at z ̃ 1 are UV-bright galaxies and have a high dust-corrected total star formation rate (SFR), with a median value of 16.9M⊙ yr-1. Their median stellar mass is log (M*/M⊙) = 9.74. We find that the dustcorrected total SFR of LBGs increases with stellar mass and that the specific SFR is lower for more massive galaxies (downsizing scenario). Only 2 per cent of the galaxies selected through the Lyman break criterion have an active galactic nucleus nature. LBGs at z ̃ 1 are located mostly over the blue cloud of the colour-magnitude diagram of galaxies at their redshift, with only the oldest and/or the dustiest deviating towards the green valley and red sequence. Morphologically, 69 per cent of LBGs are disc-like galaxies, with the fractions of interacting, compact, or irregular systems being much lower, below 12 per cent. LBGs have a median effective radius of 2.5 kpc, and larger galaxies have a higher total SFR and stellar mass. Compared with their high-redshift analogues, we find evidence that LBGs at lower redshifts are larger, redder in the UV continuum, and have a major presence of older stellar populations in their SEDs. However, we do not find significant differences in the distributions of stellar mass or dust attenuation. ©2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Oteo I.,Institute of Astrophysics of Canarias | Oteo I.,University of La Laguna | Cepa J.,Institute of Astrophysics of Canarias | Cepa J.,University of La Laguna | And 14 more authors.
Astronomy and Astrophysics | Year: 2013

Lyman-break galaxies (LBGs) represent one of the kinds of star-forming galaxies that are found in the high-redshift universe. The detection of LBGs in the far-infrared (FIR) domain can provide very important clues on their dust attenuation and total star-formation rate (SFR), allowing a more detailed study than has been performed so far. In this work we explore the FIR emission of a sample of 16 LBGs at z ∼ 3 in the GOODS-North and GOODS-South fields that are individually detected in PACS-100 μm or PACS-160 μm. These detections demonstrate the possibility of measuring the dust emission of LBGs at high redshift. We find that PACS-detected LBGs at z ∼ 3 are highly obscured galaxies which belong to the ultra-luminous or hyper-luminous IR galaxy class. Their total SFR cannot be recovered with the dust attenuation factors obtained from their UV continuum slope or their SED-derived dust attenuation employing Bruzual & Charlot (2003) templates. Both methods underestimate the results for most of the galaxies. Comparing with a sample of PACS-detected LBGs at z ∼ 1, we find evidence that the FIR emission of LBGs might have changed with redshift, in the sense that the dustiest LBGs found at z ∼ 3 have more prominent FIR emission, are dustier for a given UV slope, and have higher SFR for a given stellar mass than the dustiest LBGs found at z ∼ 1. © 2013 ESO.


Oteo I.,Institute of Astrophysics of Canarias | Oteo I.,University of La Laguna | Magdis G.,University of Oxford | Bongiovanni A.,Institute of Astrophysics of Canarias | And 62 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

In this work, we report the Photodetector Array Camera and Spectrometer (PACS) 100 μm/160 μm detections of a sample of 42 GALEX-selected and far-infrared (FIR)-detected Lyman break galaxies (LBGs) at z ~ 1 located in the Cosmic Evolution Survey (COSMOS) field and analyse their ultraviolet (UV) to FIR properties. The detection of these LBGs in the FIR indicates that they have a dust content high enough so that its emission can be directly detected. According to a spectral energy distribution (SED) fitting with stellar population templates to their UV-to-near-IR observed photometry, PACS-detected LBGs tend to be bigger (Reff ~ 4.1 kpc), more massive [log (M*/M⊙) ~ 10.7], dustier [Es(B - V) ~ 0.40], redder in the UV continuum (β ~ -0.60) and UV-brighter [log (LUV/L⊙) ~ 10.1] than PACSundetected LBGs. PACS-detected LBGs at z ~ 1 are mostly disc-like galaxies and are located over the green valley and red sequence of the colour-magnitude diagram of galaxies at their redshift. By using their UV and IR emission, we find that PACS-detected LBGs tend to be less dusty and have slightly higher total star formation rates (SFRs) than other PACS-detected UV-selected galaxies within the same redshift range. As a consequence of the selection effect due to the depth of the FIR observations employed, all our PACS-detected LBGs have total IR luminosities, LIR, higher than 1011 L⊙ and thus are luminous IR galaxies. However, none of the PACS-detected LBGs are in the ultra-luminous IR galaxy (ULIRG) regime, LIR =1012 L⊙, where the FIR observations are complete. The finding of ULIRGs-LBGs at higher redshifts (z ~ 3) suggests an evolution of the FIR emission of LBGs with cosmic time. In an IRX-β diagram, PACS-detected LBGs at z~1 tend to be located around the relation for local starburst similarly to other UV-selected PACS-detected galaxies at the same redshift. Consequently, the dust-correction factors obtained with theirUVcontinuum slope allowus to determine their total SFR, unlike at higher redshifts. However, the dust attenuation derived from UV to NIR SED fitting overestimates the total SFR for most of our PACS-detected LBGs in an age-dependent way: the overestimation factor is higher in younger galaxies. This is likely due to the typical degeneracy between dust attenuation and age in the SED fitting with synthetic templates and highlights the importance of the FIR measurements in the analysis of star-forming galaxies at intermediate redshifts. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Povic M.,Institute of Astrophysics of Canarias | Povic M.,Institute Astrofisica Of Andalucia Iaa Csic | Perez Garcia A.M.,Institute of Astrophysics of Canarias | Sanchez-Portal M.,Asociacion ASPID | And 17 more authors.
Astronomische Nachrichten | Year: 2013

Luminosity functions are one of the most important observational clues when studying galaxy evolution over cosmic time. In this paper we present the X-ray luminosity functions for X-ray detected AGN in the SXDS and GWS fields. The limiting fluxes of our samples are 9.0 ×10-15 and 4.8 ×10-16 erg cm-2 s-1 in the 0.5-7.0 keV band in the two fields, respectively. We carried out analysis in three X-ray bands and in two redshift intervals up to z ≤ 1.4. Moreover, we derive the luminosity functions for different optical morphologies and X-ray types. We confirm strong luminosity evolution in all three bands, finding the most luminous objects at higher redshift. However, no signs of density evolution are found in any tested X-ray band. We obtain similar results for compact and early-type objects. Finally, we observe the "Steffen effect", where X-ray type-1 sources are more numerous at higher luminosities in comparison with type-2 sources. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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