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Register a new userModelling High-z Galaxies from the far-UV to the far-IR
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Added by
Julien E. G. Devriendt
Publication date
1998
fields
Physics
and research's language is
English
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In this paper, we report on a first estimate of the contribution of galaxies to the diffuse extragalactic background from the far-UV to the submm, based on semi--analytic models of galaxy formation and evolution. We conclude that the global multi--wavelength picture seems to be consistent provided a quite important fraction of star--formation be hidden in dust--enshrouded systems at intermediate and high--redshift. We show that, according to such models, galaxies cannot stand as important contributors to the background hydrogen-ionizing flux at high-redshift unless neutral hydrogen absorption sites are clumpy and uncorrelated with star forming regions.We briefly discuss the robustness of such a result.
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We combine wide and deep galaxy number-count data from GAMA, COSMOS/G10, HST ERS, HST UVUDF and various near-, mid- and far- IR datasets from ESO, Spitzer and Herschel. The combined data range from the far-UV (0.15microns) to far-IR (500microns), and in all cases the contribution to the integrated galaxy light (IGL) of successively fainter galaxies converges. Using a simple spline fit, we derive the IGL and the extrapolated-IGL in all bands. We argue undetected low surface brightness galaxies and intra-cluster/group light is modest, and that our extrapolated-IGL measurements are an accurate representation of the extra-galactic background light. Our data agree with most earlier IGL estimates and with direct measurements in the far-IR, but disagree strongly with direct estimates in the optical. Close agreement between our results and recent very high-energy experiments (H.E.S.S. and MAGIC), suggest that there may be an additional foreground affecting the direct estimates. The most likely culprit could be the adopted Zodiacal light model. Finally we use a modified version of the two-component model to integrate the EBL and obtain measurements of the Cosmic Optical Background (COB) and Cosmic Infrared Background (CIB) of: $24^{+4}_{-4}$nWm$^{-2}$sr$^{-1}$ and $26^{+5}_{-5}$nWm$^{-2}$sr$^{-1}$ respectively (48:52%). Over the next decade, upcoming space missions such as Euclid and WFIRST, have the capacity to reduce the COB error to $<1%$, at which point comparisons to the very high energy data could have the potential to provide a direct detection and measurement of the reionisation field.
We present first insights into the far-IR properties for a sample of IRAC and MIPS-24um detected Lyman Break Galaxies (LBGs) at z ~ 3, as derived from observations in the northern field of the Great Observatories Origins Survey (GOODS-N) carried out with the PACS instrument on board the Herschel Space Observatory. Although none of our galaxies are detected by Herschel, we employ a stacking technique to construct, for the first time, the average spectral energy distribution of infrared luminous LBGs from UV to radio wavelengths. We derive a median IR luminosity of L_{IR} = 1.6 x 10^12 Lo, placing the population in the class of ultra luminous infrared galaxies (ULIRGs). Complementing our study with existing multi-wavelength data, we put constraints on the dust temperature of the population and find that for their L_{IR}, MIPS-LBGs are warmer than submm-luminous galaxies while they fall in the locus of the L_{IR}-T_{d} relation of the local ULIRGs. This, along with estimates based on the average SED, explains the marginal detection of LBGs in current sub-mm surveys and suggests that these latter studies introduce a bias towards the detection of colder ULIRGs in the high-z universe, while missing high-z ULIRGS with warmer dust.
We present the GAMA Panchromatic Data Release (PDR) constituting over 230deg$^2$ of imaging with photometry in 21 bands extending from the far-UV to the far-IR. These data complement our spectroscopic campaign of over 300k galaxies, and are compiled from observations with a variety of facilities including: GALEX, SDSS, VISTA, WISE, and Herschel, with the GAMA regions currently being surveyed by VST and scheduled for observations by ASKAP. These data are processed to a common astrometric solution, from which photometry is derived for 221,373 galaxies with r<19.8 mag. Online tools are provided to access and download data cutouts, or the full mosaics of the GAMA regions in each band. We focus, in particular, on the reduction and analysis of the VISTA VIKING data, and compare to earlier datasets (i.e., 2MASS and UKIDSS) before combining the data and examining its integrity. Having derived the 21-band photometric catalogue we proceed to fit the data using the energy balance code MAGPHYS. These measurements are then used to obtain the first fully empirical measurement of the 0.1-500$mu$m energy output of the Universe. Exploring the Cosmic Spectral Energy Distribution (CSED) across three time-intervals (0.3-1.1Gyr, 1.1-1.8~Gyr and 1.8---2.4~Gyr), we find that the Universe is currently generating $(1.5 pm 0.3) times 10^{35}$ h$_{70}$ W Mpc$^{-3}$, down from $(2.5 pm 0.2) times 10^{35}$ h$_{70}$ W Mpc$^{-3}$ 2.3~Gyr ago. More importantly, we identify significant and smooth evolution in the integrated photon escape fraction at all wavelengths, with the UV escape fraction increasing from 27(18)% at z=0.18 in NUV(FUV) to 34(23)% at z=0.06. The GAMA PDR will allow for detailed studies of the energy production and outputs of individual systems, sub-populations, and representative galaxy samples at $z<0.5$. The GAMA PDR can be found at: http://gama-psi.icrar.org/
Photometric data of galaxies covering the rest-frame wavelength range from far-UV to far-IR make it possible to derive galaxy properties with a high reliability by fitting the attenuated stellar emission and the related dust emission at the same time. For this purpose we wrote the code CIGALE (Code Investigating GALaxy Emission) that uses model spectra composed of the Maraston (or PEGASE) stellar population models, synthetic attenuation functions based on a modified Calzetti law, spectral line templates, the Dale & Helou dust emission models, and optional spectral templates of obscured AGN. Depending on the input redshifts, filter fluxes are computed for the model set and compared to the galaxy photometry by carrying out a Bayesian-like analysis. CIGALE was tested by analysing 39 nearby galaxies selected from SINGS. The reliability of the different model parameters was evaluated by studying the resulting expectation values and their standard deviations in relation to the input model grid. Moreover, the influence of the filter set and the quality of photometric data on the code results was estimated. For up to 17 filters between 0.15 and 160 mum, we find robust results for the mass, star formation rate, effective age of the stellar population at 4000 A, bolometric luminosity, luminosity absorbed by dust, and attenuation in the far-UV. A study of the mutual relations between the reliable properties confirms the dependence of star formation activity on morphology in the local Universe and indicates a significant drop in this activity at about 10^11 M_sol towards higher total stellar masses. The dustiest sample galaxies are present in the same mass range. [abridged]
The far-ultraviolet (UV) counts and the deep optical spectroscopic surveys have revealed an unexpected number of very blue galaxies (vBG). Using constraints from the UV and optical, we apply the galaxy evolution model PEGASE (Fioc & Rocca-Volmerange 1997, hereafter FRV) to describe this population with a cycling star formation. When added to normally evolving galaxy populations, vBG are able to reproduce UV number counts and color distributions as well as deep optical redshift distributions fairly well. Good agreement is also obtained with optical counts (including the Hubble Deep Field). The number of vBG is only a small fraction of the number of normal galaxies, even at faintest magnitudes. In our modelling, the latter explain the bulk of the excess of faint blue galaxies in an open Universe. The problem of the blue excess remains in a flat Universe without cosmological constant.
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