排序方式： 共有16条查询结果，搜索用时 15 毫秒
1.
P. Davoodi F. Pozzi S. Oliver M. Polletta A. Afonso-Luis D. Farrah E. Hatziminaoglou G. Rodighiero S. Berta I. Waddington C. Lonsdale M. Rowan-Robinson D. L. Shupe T. Evans F. Fang H. E. Smith J. Surace 《Monthly notices of the Royal Astronomical Society》2006,371(3):1113-1124
We present the rest-frame optical and infrared colours of a complete sample of 1114 z < 0.3 galaxies from the Spitzer Wide-Area Infrared Extragalactic (SWIRE) Legacy Survey and the Sloan Digital Sky Survey (SDSS). We discuss the optical and infrared colours of our sample and analyse in detail the contribution of dusty star-forming galaxies and active galactic nuclei (AGN) to optically selected red sequence galaxies.
We propose that the optical ( g − r ) colour and infrared log( L24 / L 3.6 ) colour of galaxies in our sample are determined primarily by a bulge-to-disc ratio. The ( g − r ) colour is found to be sensitive to the bulge-to-disc ratio for disc-dominated galaxies, whereas the log( L 24 / L 3.6 ) colour is more sensitive for bulge-dominated systems.
We identify ∼18 per cent (195 sources) of our sample as having red optical colours and infrared excess. Typically, the infrared luminosities of these galaxies are found to be at the high end of star-forming galaxies with blue optical colours. Using emission-line diagnostic diagrams, 78 are found to have an AGN contribution and 117 are identified as star-forming systems. The red ( g − r ) colour of the star-forming galaxies could be explained by extinction. However, their high optical luminosities cannot. We conclude that they have a significant bulge component.
The number densities of optically red star-forming galaxies are found to correspond to ∼13 per cent of the total number density of our sample. In addition, these systems contribute ∼13 per cent of the total optical luminosity density, and 28 per cent of the total infrared luminosity density of our SWIRE/SDSS sample. These objects may reduce the need for 'dry mergers'. 相似文献
We propose that the optical ( g − r ) colour and infrared log( L
We identify ∼18 per cent (195 sources) of our sample as having red optical colours and infrared excess. Typically, the infrared luminosities of these galaxies are found to be at the high end of star-forming galaxies with blue optical colours. Using emission-line diagnostic diagrams, 78 are found to have an AGN contribution and 117 are identified as star-forming systems. The red ( g − r ) colour of the star-forming galaxies could be explained by extinction. However, their high optical luminosities cannot. We conclude that they have a significant bulge component.
The number densities of optically red star-forming galaxies are found to correspond to ∼13 per cent of the total number density of our sample. In addition, these systems contribute ∼13 per cent of the total optical luminosity density, and 28 per cent of the total infrared luminosity density of our SWIRE/SDSS sample. These objects may reduce the need for 'dry mergers'. 相似文献
2.
T. S. R. Babbedge M. Rowan-Robinson M. Vaccari J. A. Surace C. J. Lonsdale D. L. Clements F. Fang D. Farrah A. Franceschini E. Gonzalez-Solares E. Hatziminaoglou C. G. Lacey S. Oliver N. Onyett I. Pérez-Fournon M. Polletta F. Pozzi G. Rodighiero D. L. Shupe B. Siana H. E. Smith 《Monthly notices of the Royal Astronomical Society》2006,370(3):1159-1180
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E. Hatziminaoglou P. Cassata G. Rodighiero I. Pérez-Fournon A. Franceschini A. Hernán-Caballero F. M. Montenegro-Montes A. Afonso-Luis T. Jarrett G. Stacey C. Lonsdale F. Fang S. Oliver M. Rowan-Robinson D. Shupe H. E. Smith J. Surace C. K. Xu E. A. González-Solares 《Monthly notices of the Royal Astronomical Society》2005,364(1):47-58
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E. Hatziminaoglou J. Fritz A. Franceschini A. Afonso-Luis A. Hernán-Caballero I. Pérez-Fournon S. Serjeant C. Lonsdale S. Oliver M. Rowan-Robinson D. Shupe H. E. Smith J. Surace 《Monthly notices of the Royal Astronomical Society》2008,386(3):1252-1264
We derive the properties of dusty tori in active galactic nuclei from the comparison of observed spectral energy distributions (SEDs) of SDSS quasars and a precomputed grid of torus models. The observed SEDs comprise SDSS photometry, Two-Micron All-Sky Survey J , H and K data, whenever available, and mid-infrared (mid-IR) data from the Spitzer Wide-area InfraRed Extragalactic Survey. The adopted model is that of Fritz, Franceschini & Hatziminaoglou. The fit is performed by standard χ2 -minimization; the model, however, can be a multicomponent comprising a stellar and a starburst component, whenever necessary. Models with low equatorial optical depth, τ9.7 , were allowed as well as 'traditional' models with τ9.7 ≥ 1.0 , corresponding to A V ≥ 22 and the results were compared. Fits using high optical depth tori models only produced dust more compactly distributed than in the configuration where all τ9.7 models were permitted. Tori with decreasing dust density with the distance from the centre were favoured while there was no clear preference for models with or without angular variation of the dust density. The computed outer radii of the tori are of some tens of parsecs large but can reach, in a few cases, a few hundreds of parsecs. The mass of dust, M Dust , and IR luminosity, L IR , integrated in the wavelength range between 1 and 1000 μm, do not show significant variations with redshift, once the observational biases are taken into account. Objects with 70-μm detections, representing 25 per cent of the sample, are studied separately and the starburst contribution (whenever present) to the IR luminosity can reach, in the most extreme but very few cases, 80 per cent. 相似文献
7.
P. Padovani D. M. Alexander R. J. Assef B. De Marco P. Giommi R. C. Hickox G. T. Richards V. Smolčić E. Hatziminaoglou V. Mainieri M. Salvato 《Astronomy and Astrophysics Review》2017,25(1):2
Active galactic nuclei (AGN) are energetic astrophysical sources powered by accretion onto supermassive black holes in galaxies, and present unique observational signatures that cover the full electromagnetic spectrum over more than twenty orders of magnitude in frequency. The rich phenomenology of AGN has resulted in a large number of different “flavours” in the literature that now comprise a complex and confusing AGN “zoo”. It is increasingly clear that these classifications are only partially related to intrinsic differences between AGN and primarily reflect variations in a relatively small number of astrophysical parameters as well the method by which each class of AGN is selected. Taken together, observations in different electromagnetic bands as well as variations over time provide complementary windows on the physics of different sub-structures in the AGN. In this review, we present an overview of AGN multi-wavelength properties with the aim of painting their “big picture” through observations in each electromagnetic band from radio to \(\gamma \)-rays as well as AGN variability. We address what we can learn from each observational method, the impact of selection effects, the physics behind the emission at each wavelength, and the potential for future studies. To conclude, we use these observations to piece together the basic architecture of AGN, discuss our current understanding of unification models, and highlight some open questions that present opportunities for future observational and theoretical progress. 相似文献
8.
Multiwavelength observations of the two unidentified EGRET sources 3EG J0616-3310 and 3EG J1249-8330
N. La Palombara R. P. Mignani E. Hatziminaoglou M. Schirmer G. F. Bignami P. Caraveo 《Astrophysics and Space Science》2007,309(1-4):209-213
We report on the X-ray and optical observation of the two unidentified EGRET sources 3EG J0616-3310 and 3EG J1249-8330. The X-ray coverage performed by the ESA space telescope XMM–Newton provided ∼150 X-ray sources within each of the two γ-ray error-circles. The optical follow-up carried on with the Wide Field Imager at the ESO/MPG 2.2 m telescope have found no candidate counterpart for 125 of these X-ray sources. Among these, we have selected
9 sources with f
X/f
opt≥100, which we consider promising INS candidates. 相似文献
9.
Stephen Serjeant Evanthia Hatziminaoglou 《Monthly notices of the Royal Astronomical Society》2009,397(1):265-280
We have used far-infrared data from IRAS , Infrared Space Observatory ( ISO ), Spitzer Wide-Area Infrared Extragalactic (SWIRE), Submillimetre Common User Bolometer Array (SCUBA) and Max-Planck Millimetre Bolometer (MAMBO) to constrain statistically the mean far-infrared luminosities of quasars. Our quasar compilation at redshifts 0 < z < 6.5 and I -band luminosities −20 < I AB < −32 is the first to distinguish evolution from quasar luminosity dependence in such a study. We carefully cross-calibrate IRAS against Spitzer and ISO , finding evidence that IRAS 100-μm fluxes at <1 Jy are overestimated by ∼30 per cent. We find evidence for a correlation between star formation in quasar hosts and the quasar optical luminosities, varying as star formation rate (SFR) ∝ L 0.44±0.07 opt at any fixed redshift below z = 2 . We also find evidence for evolution of the mean SFR in quasar host galaxies, scaling as (1 + z )1.6±0.3 at z < 2 for any fixed quasar I -band absolute magnitude fainter than −28. We find no evidence for any correlation between SFR and black hole mass at 0.5 < z < 4 . Our data are consistent with feedback from black hole accretion regulating stellar mass assembly at all redshifts. 相似文献
10.
Nicola La Palombara Patrizia Caraveo Roberto Mignani Evanthia Hatziminaoglou Giovanni F. Bignami Mischa Schirmer 《Astrophysics and Space Science》2005,297(1-4):335-344
Most counterparts of the identified low-latitude γ-ray sources are isolated neutron stars (INSs). Since INSs are characterized by an extremely high value of f
X/f
opt, a systematic X-ray/optical coverage of the fields of unidentified low-latitude γ-ray sources is the best way to unveil INS
counterparts of unidentified sources. Since the low-latitude sources are heavily affected by the interstellar absorption in
both the X-ray and optical bands, we decided to apply the above strategy to two middle-latitude EGRET sources, which could belong to a local galactic population: 3EG J0616-3310 and 3EG J1249-8330. Here we report on the global
X-ray characterization of about 300 objects, on their candidate optical counterparts and on the preliminary results of their
identification. 相似文献