Browsing by Author "Cepa, J."
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- ItemEnhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations(2012) Santini, P.; Rosario, D. J.; Shao, L.; Lutz, D.; Maiolino, R.; Alexander, D. M.; Altieri, B.; Andreani, P.; Aussel, H.; Bauer, F. E.; Berta, S.; Bongiovanni, A.; Brandt, W. N.; Brusa, M.; Cepa, J.; Cimatti, A.; Daddi, E.; Elbaz, D.; Fontana, A.; Schreiber, N. M. Foerster; Genzel, R.; Grazian, A.; Le Floc'h, E.; Magnelli, B.; Mainieri, V.; Nordon, R.; Garcia, A. M. Perez; Poglitsch, A.; Popesso, P.; Pozzi, F.; Riguccini, L.; Rodighiero, G.; Salvato, M.; Sanchez-Portal, M.; Sturm, E.; Tacconi, L. J.; Valtchanov, I.; Wuyts, S.We compare the average star formation (SF) activity in X-ray selected AGN hosts with a mass-matched control sample of inactive galaxies, including both star forming and quiescent sources, in the 0.5 < z < 2.5 redshift range. Recent observations carried out by PACS, the 60-210 mu m photometric camera on board the Herschel Space Observatory, in GOODS-S, GOODS-N and COSMOS allow us to obtain an unbiased estimate of the far-IR luminosity, and hence of the SF properties, of the two samples. Accurate AGN host stellar mass estimates are obtained by decomposing their total emission into the stellar and the nuclear components. We report evidence of a higher average SF activity in AGN hosts with respect to the control sample of inactive galaxies. The level of SF enhancement is modest (similar to 0.26 dex at similar to 3 sigma confidence level) at low X-ray luminosities (L-X less than or similar to 10(43.5) erg s(-1)) and more pronounced (0.56 dex at >10 sigma confidence level) in the hosts of luminous AGNs. However, when comparing to star forming galaxies only, AGN hosts are found broadly consistent with the locus of their "main sequence". We investigate the relative far-IR luminosity distributions of active and inactive galaxies, and find a higher fraction of PACS detected, hence normal and highly star forming systems among AGN hosts. Although different interpretations are possible, we explain our findings as a consequence of a twofold AGN growth path: faint AGNs evolve through secular processes, with instantaneous AGN accretion not tightly linked to the current total SF in the host galaxy, while the luminous AGNs co-evolve with their hosts through periods of enhanced AGN activity and star formation, possibly through major mergers. While an increased SF activity with respect to inactive galaxies of similar mass is expected in the latter, we interpret the modest SF offsets measured in low-L-X AGN hosts as either a) generated by non-synchronous accretion and SF histories in a merger scenario or b) due to possible connections between instantaneous SF and accretion that can be induced by smaller scale (non-major merger) mechanisms. Far-IR luminosity distributions favour the latter scenario.
- ItemHerschel FIR counterparts of selected Lyα emitters at z ∼ 2.2 Fast evolution since z ∼ 3 or missed obscured AGNs?(2010) Bongiovanni, A.; Oteo, I.; Cepa, J.; Perez Garcia, A. M.; Sanchez-Portal, M.; Ederoclite, A.; Aguerri, J. A. L.; Alfaro, E. J.; Altieri, B.; Andreani, P.; Aparicio-Villegas, M. T.; Aussel, H.; Benitez, N.; Berta, S.; Broadhurst, T.; Cabrera-Cano, J.; Castander, F. J.; Cava, A.; Cervino, M.; Chulani, H.; Cimatti, A.; Cristobal-Hornillos, D.; Daddi, E.; Dominguez, H.; Elbaz, D.; Fernandez-Soto, A.; Schreiber, N. Foerster; Genzel, R.; Gomez, M. F.; Gonzalez Delgado, R. M.; Grazian, A.; Gruppioni, C.; Herreros, J. M.; Iglesias Groth, S.; Infante, L.; Lutz, D.; Magnelli, B.; Magdis, G.; Maiolino, R.; Marquez, I.; Martinez, V. J.; Masegosa, J.; Moles, M.; Molino, A.; Nordon, R.; del Olmo, A.; Perea, J.; Poglitsch, A.; Popesso, P.; Pozzi, F.; Prada, F.; Quintana, J. M.; Riguccini, L.; Rodighiero, G.; Saintonge, A.; Sanchez, S. F.; Santini, P.; Shao, L.; Sturm, E.; Tacconi, L.; Valtchanov, I.Ly alpha emitters (LAEs) are seen everywhere in the redshift domain from local to z similar to 7. Far-infrared (FIR) counterparts of LAEs at different epochs could provide direct clues on dust content, extinction, and spectral energy distribution (SED) for these galaxies. We search for FIR counterparts of LAEs that are optically detected in the GOODS-North field at redshift z similar to 2.2 using data from the Herschel Space Telescope with the Photodetector Array Camera and Spectrometer (PACS). The LAE candidates were isolated via color-magnitude diagram using the medium-band photometry from the ALHAMBRA Survey, ancillary data on GOODS-North, and stellar population models. According to the fitting of these spectral synthesis models and FIR/optical diagnostics, most of them seem to be obscured galaxies whose spectra are AGN-dominated. From the analysis of the optical data, we have observed a fraction of AGN or composite over source total number of similar to 0.75 in the LAE population at z similar to 2.2, which is marginally consistent with the fraction previously observed at z = 2.25 and even at low redshift (0.2 < z < 0.45), but significantly different from the one observed at redshift similar to 3, which could be compatible either with a scenario of rapid change in the AGN fraction between the epochs involved or with a non detection of obscured AGN in other z = 2-3 LAE samples due to lack of deep FIR observations. We found three robust FIR (PACS) counterparts at z similar to 2.2 in GOODS-North. This demonstrates the possibility of finding dust emission in LAEs even at higher redshifts.
- ItemStellar populations of galaxies in the ALHAMBRA survey up to z ∼ 1 III. The stellar content of the quiescent galaxy population during the last 8 Gyr(2019) Diaz-Garcia, L.A.; Cenarro, A.J.; Lopez-Sanjuan, C.; Ferreras, I.; Fernandez-Soto, A.; Delgado, R.M.G.; Marquez, I.; Masegosa, J.; San Roman, I.; Infante Lira, Leopoldo; Viironen, K.; Bonoli, S.; Cerviño, M.; Moles, M.; Cristóbal-Hornillos, D.; Alfaro, E.; Aparicio-Villegas, T.; Benítez, N.; Broadhurst, T.; Cabrera-Caño, J.; Castander, F.J.; Cepa, J.; Husillos, C.; Aguerri, J.A.L.; Martínez, V.J.; Molino, A.; del Olmo, A.; Perea, J.; Prada, F.; Quintana, J.M.
- ItemStellar populations of galaxies in the ALHAMBRA survey up to z∼1 II. Stellar content of quiescent galaxies within the dust-corrected stellar mass–colour and the UVJ colour–colour diagrams(2019) Diaz-Garcia, L.A.; Cenarro, A.J.; Lopez-Sanjuan, C.; Ferreras, I.; Cervino, M.; Fernandez-Soto, A.; Delgado, R.M.G.; Marquez, I.; Povic, M.|Infante Lira, Leopoldo; San Roman, I.; Viironen, K.; Moles, M.; Cristobal-Hornillos, D.; Lopez-Comazzi, A.; Alfaro, E.; Aparicio-Villegas, T.; Benitez, N.; Broadhurst, T.; Cabrera-Cano, J.; Castander, F.J.; Cepa, J.; Husillos, César; Aguerri, J.A.L.; Martínez, V.J.; Masegosa, Josefa; Molino, A.; Olmo, Ascensión del; Perea, Jaime; Prada, Francisco; Quintana, José María
- ItemThe ALHAMBRA survey(2008) Moles, M.; Benitez, N.; Aguerri, J. A. L.; Alfaro, E. J.; Broadhurst, T.; Cabrera-Cano, J.; Castander, F. J.; Cepa, J.; Cervino, M.; Cristobal-Hornillos, D.; Fernandez-Soto, A.; Delgado, R. M. Gonzalez; Infante, L.; Marquez, I.; Martinez, V. J.; Masegosa, J.; del Olmo, A.; Perea, J.; Prada, F.; Quintana, J. M.; Sanchez, S. F.Here we describe the first results of the Advanced Large Homogeneous Area Medium-Band Redshift Astronomical (ALHAMBRA) survey, which provides cosmic tomography of the evolution of the contents of the universe overmost of cosmic history. Our novel approach employs 20 contiguous, equal-width, medium-band filters covering from 3500 angstrom to 9700 angstrom, plus the standard JHK(s) near-infrared (NIR) bands, to observe a total area of 4 deg(2) on the sky. The optical photometric system has been designed to maximize the number of objects with accurate classification by spectral energy distribution type and redshift, and to be sensitive to relatively faint emission features in the spectrum. The observations are being carried out with the Calar Alto 3.5 m telescope using the wide-field cameras in the optical, Large Area Imager for Calar Alto, and in the NIR, Omega-2000. The first data confirm that we are reaching the expected magnitude limits (for a total of 100 ks integration time per pointing) of AB <= 25 mag (for an unresolved object, signal-to-noise ratio = 5) in the optical filters from the blue to 8300 angstrom, and from AB = 24.7 to 23.4 for the redder ones. The limit in the NIR, for a total of 15 ks exposure time per pointing, is (in the Vega system) K-s approximate to 20 mag, H approximate to 21 mag, J approximate to 22 mag. Some preliminary results are presented here to illustrate the capabilities of the ongoing survey. We expect to obtain accurate redshift values, Delta z/(1+z) <= 0.03 for about five x 10(5) galaxies with 1 <= 25 (60% completeness level), and z(med) = 0.74. This accuracy, together with the homogeneity of the selection function, will allow for the study of the redshift evolution of the large-scale structure, the galaxy population and its evolution with redshift, the identification of clusters of galaxies, and many other studies, without the need for any further follow-up. It will also provide targets for detailed studies with 10 m class telescopes. Given its area, spectral coverage, and its depth, apart from those main goals, the ALHAMBRA survey will also produce valuable data for galactic studies.
- ItemThe ALHAMBRA survey: Discovery of a faint QSO at z=5.41 (Research Note)(2013) Matute, I.; Masegosa, J.; Marquez, I.; Fernandez-Soto, A.; Husillos, C.; del Olmo, A.; Perea, J.; Povic, M.; Ascaso, B.; Alfaro, E. J.; Moles, M.; Aguerri, J. A. L.; Aparicio-Villegas, T.; Benitez, N.; Broadhurst, T.; Cabrera-Cano, J.; Castander, F. J.; Cepa, J.; Cervino, M.; Cristobal-Hornillos, D.; Infante, L.; Gonzalez Delgado, R. M.; Martinez, V. J.; Molino, A.; Prada, F.; Quintana, J. M.Aims. We aim to illustrate the potentiality of the Advanced Large, Homogeneous Area, Medium-Band Redshift Astronomical (ALHAMBRA) survey to investigate the high-redshift universe through the detection of quasi stellar objects (QSOs) at redshifts higher than 5.
- ItemThe mean star formation rate of X-ray selected active galaxies and its evolution from z ∼ 2.5: results from PEP-Herschel(2012) Rosario, D. J.; Santini, P.; Lutz, D.; Shao, L.; Maiolino, R.; Alexander, D. M.; Altieri, B.; Andreani, P.; Aussel, H.; Bauer, F. E.; Berta, S.; Bongiovanni, A.; Brandt, W. N.; Brusa, M.; Cepa, J.; Cimatti, A.; Cox, T. J.; Daddi, E.; Elbaz, D.; Fontana, A.; Schreiber, N. M. Foerster; Genzel, R.; Grazian, A.; Le Floch, E.; Magnelli, B.; Mainieri, V.; Netzer, H.; Nordon, R.; Garcia, I. Perez; Poglitsch, A.; Popesso, P.; Pozzi, F.; Riguccini, L.; Rodighiero, G.; Salvato, M.; Sanchez-Portal, M.; Sturm, E.; Tacconi, L. J.; Valtchanov, I.; Wuyts, S.We study relationships between star-formation rate (SFR) and the accretion luminosity and nuclear obscuration of X-ray selected active galactic nuclei (AGNs) using a combination of deep far-infrared (FIR) and X-ray data in three key extragalactic survey fields (GOODS-South, GOODS-North and COSMOS), as part of the PACS Evolutionary Probe (PEP) program. The use of three fields with differing areas and depths enables us to explore trends between the global FIR luminosity of the AGN hosts and the luminosity of the active nucleus across 4.5 orders of magnitude in AGN luminosity (L-AGN) and spanning redshifts from the Local Universe to z = 2.5. Using imaging from the Herschel/PACS instrument in 2-3 bands, we combine FIR detections and stacks of undetected objects to arrive at mean fluxes for subsamples in bins of redshift and X-ray luminosity. We constrain the importance of AGN-heated dust emission in the FIR and confirm that the majority of the FIR emission of AGNs is produced by cold dust heated by star-formation in their host galaxies.