Search

Aims. We want to study the IR (>$8\;\mu$m) emission of galaxies selected on the basis of their rest-frame UV light in a very homogeneous way (wavelength and luminosity) from $z = 0$to $z=1$. We compare their UV and IR rest-frame emission to study the evolution in dust attenuation with zas well as to check if a UV selection is capable of tracking all star formation. This UV selection will also be compared to a sample of Lyman break galaxies selected at $z \simeq 1$.

Aims. We investigate whether the mean star formation activity of star-forming galaxies from $z=0$to $z=0.7$in the GOODS-S field can be reproduced by simple evolution models of these systems. In this case, such models might be used as first-order references for studies at higher zto decipher when and to what extent a secular evolution is sufficient to explain the star formation history in galaxies.

Aims.The total infrared (TIR: 8-1000 μm) and far-ultraviolet (FUV: ~1500 Å) luminosity functions of galaxies and the related luminosity densities $\rho_{\rm TIR}$and $\rho_{\rm FUV}$are known to evolve at differemt rates from $z = 0$to z~1: the galaxy populations appear to be brighter in the past at both wavelengths, but the evolution in the TIR is larger than in the FUV. This leads to an increase of the ratio of TIR to FUV luminosity densities $\rho_{\rm TIR}/\rho_{\rm FUV}$which can be interpreted as a global increase of the dust attenuation from $z = 0$to z~ 1. Our aim is to understand the origin of this increase: is it entirely due to a variation of the dust attenuation with the luminosity of the galaxies as seen as $z = 0$or are properties of galaxies evolving with the redshift?

We investigate the possibility of searching for metal-poor high column density ($\ga$$10^{23}~{\rm cm}^{-2}$) clouds at high redshift (z) by using gamma ray burst afterglows. Such clouds could be related to primeval galaxies that may cause a burst of star formation. We show that a large part of hydrogen is in molecular form in such a high column density environment. Therefore, hydrogen molecules (H2) rather than hydrogen atoms should be searched for. Then we show that infrared H2lines are detectable for metal-poor ($\la$0.01 solar metallicity) high column density ($\log N_{\rm H}~[{\rm cm}^{-2}]\ga 23.5$) systems at high-zwithout suffering dust extinction. The optical properties of dust in infrared could also be constrained by observations of high column density systems. Some possible scenarios for producing high column density systems are finally discussed in the context of galaxy evolution.

Aims.We present the first large, unbiased sample of Lyman Break Galaxies (LBGs) at $z \sim 1$. Far ultraviolet-dropout (1530 Å) galaxies in the Chandra Deep Field South have been selected using GALEXdata. This first large sample in the $z \sim 1$universe provides us with a high quality reference sample of LBGs. Methods.We analyzed the sample from the UV to the IR using GALEX, SPITZER, ESOand HSTdata.Results.The morphology (obtained from GOODS data) of 75% of our LBGs is consistent with a disk. The vast majority of LBGs with an IR detection are also Luminous Infrared Galaxies (LIRGs). As a class, the galaxies not detected at 24 μm are an order of magnitude fainter relative to the UV compared with those detected individually, suggesting that there may be two types of behavior within the sample. For the IR-bright galaxies, there is an apparent upper limit for the UV dust attenuation and this upper limit is anti-correlated with the observed UV luminosity. Previous estimates of dust attenuations based on the ultraviolet slope are compared to new ones based on the FIR/UV ratio (for LBGs detected at 24 μm), which is usually a more reliable estimator. Depending on the calibration we use to estimate the total IR luminosity, β-based attenuations AFUVare larger by 0.2 to 0.6 mag. than the ones estimated from FIR/UV ratio. Finally, for IR-bright LBGs, median estimated β-based SFRs are 2-3 times larger than the total SFRs estimated as ${\it SFR}_{\rm TOT} = {\it SFR}_{\rm UV} + {\it SFR}_{\rm IR}$while IR-based SFRs provide values below ${\it SFR}_{\rm TOT}$by 15-20%. We use a stacking method to statistically constrain the $24~\mu$m flux of LBGs non individually detected. The results suggest that these LBGs do not contain large amounts of dust.

We constructed a local luminosity function (LF) of galaxies using a flux-limited sample ($S_{170} \ge 0.195~\mbox{Jy}$) of 55 galaxies at $z < 0.3$taken from the ISOFIRBACK survey at 170 μm. The overall shape of the 170-μm LF is found to be different from that of the total 60-μm LF (Takeuchi et al. 2003): the bright end of the LF declines more steeply than that of the 60-μm LF. This behavior is quantitatively similar to the LF of the cool subsample of the IRASPSCzgalaxies. We also estimated the strength of the evolution of the LF by assuming the pure luminosity evolution (PLE): $L(z) \propto (1+z)^Q$. We obtained $Q=5.0^{+2.5}_{-0.5}$which is similar to the value obtained by recent Spitzerobservations, in spite of the limited sample size. Then, integrating over the 170-μm LF, we obtained the local luminosity density at $170\;\mu$m, $\rho_L(170\;\mu\mbox{m})$. A direct integration of the LF gives $\rho_L(170\;\mu\mbox{m}) = 1.1 \times 10^8 h \;L_\odot \;\mbox{Mpc}^{-3}$, whilst if we assume a strong PLE with $Q=5$, the value is $5.2 \times 10^{7} h \; L_\odot \;\mbox{Mpc}^{-3}$. This is a considerable contribution to the local FIR luminosity density. By summing up with other available infrared data, we obtained the total dust luminosity density in the Local Universe, $\rho_L(\mbox{dust})=1.1 \times 10^{8}h\;L_\odot \;\mbox{Mpc}^{-3}$. Using this value, we estimated the cosmic star formation rate (SFR) density hidden by dust in the Local Universe. We obtained $\rho_{\rm SFR}(\mbox{dust}) \simeq 1.1\mbox{--}1.2\, h \times 10^{-2} \; M_\odot \,\mbox{yr}^{-1}\, \mbox{Mpc}^{-3}$, which means that 59% of the star formation is obscured by dust in the Local Universe.

The ratio between far-ultraviolet (FUV) and infrared (IR) luminosity densities from $z=0$to $z=1$is discussed by using the luminosity functions (LFs) of both wavelengths. The FUV LF ($z=0\mbox{--}1$) based on GALEXhas been reported by (Arnouts et al. (2005, ApJ, 619, L43), whilst for the IR LF, we used the IRASPSCz60-μm LF for the local universe and the Spitzer15-μm LF at higher-zas used by Le Floc'h et al. (2005, ApJ, in press). Both luminosity densities show a significant evolutionary trend, but the IR evolves much faster than the FUV. Consequently, the ratio $\rho_{\rm dust}/\rho_{\rm FUV}$increases toward higher-z, from ∼4 (local) to ∼15 ($z\simeq 1$). It is also shown that more than $70\%$of the star formation activity in the universe is obscured by dust at $0.5 \la z \la 1.2$.

The infrared (IR) emission plays a crucial role in understanding the star formation in galaxies hidden by dust. We first examined four estimators of the IR luminosity of galaxies, LFIR[CITE], LTIR[CITE], revised version of LTIR[CITE] (we denote LTIR2), and LIR[CITE] by using the observed SEDs of well-known galaxies. We found that LIRprovides excellent estimates of the total IR luminosity for a variety of galaxy SEDs. The performance of LTIR2was also found to be very good. Using LIR, we then statistically analyzed the IRASPSCzgalaxy sample [CITE] and found useful formulae relating the MIR monochromatic luminosities [ $L(12\,\mu\mbox{m})$and $L(25\,\mu\mbox{m})$] and LIR. For this purpose we constructed a subsample of 1420 galaxies with all four IRASband (12, 25, 60, and $100\,\mu$m) flux densities. We found linear relations between LIRand MIR luminosities, $L(12\,\mu\mbox{m})$and $L(25\,\mu\mbox{m})$. The prediction error with a 95% confidence level is a factor of 4–5. Hence, these formulae are useful for the estimation of the total IR luminosity only from $12\,\mu$m or $25\,\mu$m observations. We further tried to make an “interpolation” formula for galaxies at $0

Lyman-break galaxies (LBGs) contain a non-negligible amount of dust. Takeuchi (2003a, MNRAS, 343, 839) (T03) constructed a model of the infrared spectral energy distribution (SED) for very young galaxies by taking into account the dust size distribution in the early stage of galaxy evolution, which can be different from that of present-day evolved galaxies. We applied the T03 model to LBGs and constructed their expected SED. In order to examine the grain size distribution of dust, we calculated the SEDs based on two distinct types of the distribution models: a single-sized distribution and a power-law distribution with a slope of ${\rm d}N/{\rm d}a \propto a^{-3.5}$. We found that the single-sized and power-law dust size distributions yield a very similar detectability of LBGs at submillimetres (submm). We also found that galaxies with a power-law dust distribution have much less flux in the mid-infrared (MIR) than the other type. By making use of this fact we will be able to explore the dust grain size distribution in high-redshift galaxies through (observer-frame) FIR observations in future observations. We then applied the model to a gravitationally lensed LBG MS 1512-cB58(cB58), a unique probe of the dust emission from LBGs. Observations by SCUBA suggest that the galaxy has hot dust. Our model well reproduced the hot dust temperature under natural physical assumptions for the star formation rate (SFR), starburst age, and the radius of the star forming region in this galaxy. We also examined the detectability of LBGs at submm wavelengths in an eight-hour deep survey by ALMA. The LBG population with an age ${\ga} 10^8\,{\rm yr}$and a ${\rm SFR} \ga 10\,M_\odot ~{\rm yr}^{-1}$can be detected in such a survey. By integrating over their redshifted SEDs with the observed luminosity functions, we obtained the contribution of LBGs to the cosmic infrared background radiation (CIRB). Although they have a non-negligible amount of dust, their contribution was found to be small, especially in the ${\rm FIR} \sim 200\,\mu$m. Thus, we need a strongly obscured population of galaxies which contains a large amount of star formation, at some epoch in the history of the universe.

Using a graph-theoretical approach, we compared the galaxy distributions in a flux-limited galaxy sample extracted from the Lyon-Meudon Extragalactic Database (”the LEDA subsample”) with those in cosmological $N$-body simulations. To derive information on the density parameter of our Universe, we used CDM simulations with ($\Omega_{\rm 0}$, $\lambda_{\rm 0}) = (0.1$, 0.9), (0.5, 0.5), (1.0, 0.0), and prepared artificial samples. Constellation graphs were constructed from the galaxy distributions in the LEDA subsample and those in these artificial samples, and graph theory was applied. For statistical comparison, the mean absolute deviations of the distribution functions of the eigenvalues of the adjacency matrices were calculated. From our analysis we found that a low-density parameter is preferable, although the LEDA subsample we used in this study is not deep enough to provide a definite estimate of the cosmological parameter set of the Universe.

Context.The nearby universe remains the best laboratory to understand the physical properties of galaxies and is a reference for any comparison with high redshift observations. The all sky (or very large) surveys that have been performed from the ultraviolet (UV) to the far-infrared (far-IR) provide us with large datasets of very large wavelength coverage to perform a reference study.

Aims. We aim to reveal environmental dependence of infrared luminosity functions (IR LFs) of galaxies at z~ 0.8 using the AKARI satellite. AKARI's wide field of view and unique mid-IR filters help us to construct restframe 8 μm LFs directly without relying on SED models. Methods. We construct restframe 8 μm IR LFs in the cluster region RXJ1716.4+6708 at z= 0.81, and compare them with a blank field using the AKARI north ecliptic pole deep field data at the same redshift. AKARI's wide field of view (10'× 10') is suitable to investigate wide range of galaxy environments. AKARI's 15 μm filter is advantageous here since it directly probes restframe 8 μm at z~ 0.8, without relying on a large extrapolation based on a SED fit, which was the largest uncertainty in previous work. Results. We have found that cluster IR LFs at restframe 8 μm have a factor of 2.4 smaller $L^*$and a steeper faint-end slope than that of the field. Confirming this trend, we also found that faint-end slopes of the cluster LFs becomes flatter and flatter with decreasing local galaxy density. These changes in LFs cannot be explained by a simple infall of field galaxy population into a cluster. Physics that can preferentially suppress IR luminous galaxies in high density regions is required to explain the observed results.