We present ISOCAM 15 μm and MIPS 24 μm photometry of a sample of 16 distant Luminous Infrared Galaxies (LIRGs) characterized by a median luminosity $L_{\rm IR} \sim$ 2 $\times$ 10$^{11}~L_{\odot}$ ...and redshift $z = 0.7$ (distributed from $z = 0.1$ to 1.2). While some sources display 24/15 μm flux ratios also consistent with a featureless continuum dominating their mid-infrared (MIR) spectral energy distributions (SEDs), the presence of prominent emission features such as the Polycyclic Aromatic Hydrocarbons is clearly required to explain the observed colors for more than half of the sample. As a result, a general good agreement is observed between the data and predictions from the local starburst-dominated SEDs that have been used so far to constrain IR galaxy evolution. This is consistent with the star-forming nature of LIRGs derived from previous works, even though our approach cannot rule out the dominance of an AGN in some cases. Our study also supports the possibility of tracing the total IR luminosity of distant galaxies (up to $z\sim$ 1) from their MIR emission.
We investigate the environment of infrared-luminous galaxies image . We focus on the redshift range image, where these galaxies dominate the star formation activity and play a significant role in ...galaxy evolution. We employ MIPS 24 mum data to identify infrared galaxies in the Extended Groth Strip (EGS). We use a local density indicator to probe the environment on a few Mpc scales and a group member catalog, both of which make use of the DEEP2 spectroscopic redshift catalog, to quantify the environment of these galaxies. We find that the local environment of LIRGs and ULIRGs is intermediate between that of blue and red galaxies. LIRGs and ULIRGs avoid underdense environments and inhabit local environments that are more dense on average than those of other DEEP2 galaxies at similar redshifts. However, when the comparison sample of the non-IR DEEP2 galaxies is restricted to have the same range of stellar mass, color, or luminosity as the IR galaxies, there is no longer any significant difference in environment: the IR galaxies follow the same trends in the color-environment and luminosity-environment relations observed at image. We also find that about 30% of the LIRGs and ULIRGs belong to groups, associated with a minimum dark matter halo of image M sub(image) h super(-1). The group members constitute 20% of the sources responsible for the IR star formation rate density and comoving energy density at image.
We study the infrared (IR) properties of high-redshift galaxies using deep Spitzer 24, 70, and 160 km data. Our primary interest is to improve the constraints on the total IR luminosities, Lir, of ...these galaxies. We combine the Spitzer data in the southern Extended Chandra Deep Field with a K(s-band-selected galaxy sample and photometric redshifts from the Multiwavelength Survey by Yale-Chile. We used a stacking analysis to measure the average 70 and 160 km flux densities of 1.5 < z < 2.5 galaxies as a function of 24 km flux density, X-ray activity, and rest-frame near-IR color. Galaxies with 1.5 < z < 2.5 and unk = 53-250 kJy have Lir derived from their average 24-160 km flux densities within factors of 2-3 of those inferred from the 24 km flux densities only. However, Lir derived from the average 24-160 km flux densities for galaxies with S(24) > 250 kJy and 1.5 < z < 2.5 are lower than those Inferred using only the 24 km flux density by factors of 2-10. Galaxies with S(24) > 250 kJy have S(70)/S(24) flux ratios comparable to sources with X-ray detections or red rest-frame IR colors, suggesting that warm dust possibly heated by AGNs may contribute to the high 24 km emission. Based on the average 24-160 kum flux densities, nearly all 24 km-selected galaxies at 1.5 < z < 2.5 have Lir < 6 x 10(12) L unk, which, if attributed to star formation, corresponds to unk < 1000 M unk yr(-1). This suggests that high-redshift galaxies may have star formation efficiencies and feedback processes similar to those of local analogs. Objects with Lir > 6 x 10(12) L unk are quite rare, with a surface density 630 c 10 deg(-2), corresponding to 62 c 1 x 10(-6) Mpc(-3) over 1.5 < z < 2.5.
We describe two peculiar galaxies falling into the massive galaxy clusters Abell 1689 (z≈ 0.18) and Abell 2667 (z≈ 0.23), respectively. Hubble Space Telescope (HST) images show extraordinary trails ...composed of bright blue knots (−16.5 < M < −11.5 mag) and stellar streams associated with each of these systems. Combining optical, near- and mid-infrared and radio observations we prove that while both galaxies show similar extended trails of star-forming knots, their recent star formation histories are different. One (≈L*) is experiencing a strong burst of star formation, appearing as a rare example of a luminous infrared cluster galaxy. In comparison, the other (≈0.1L*) has recently ceased its star formation activity. Our model suggests that the morphologies and star formation in these galaxies have been influenced by the combined action of tidal interaction (likely with the cluster potential) and of ram pressure with the intracluster medium (ICM). These results can be used to gain more insights to the origin of S0s, dwarf and ultracompact dwarf (UCD) cluster galaxies.
Emmanuel Levinas et Michel Serres commentent et réécrivent deux épisodes de L'Odyssée d'Homère où Ulysse est confronté à l'animal : le premier s'attache à la reconnaissance d'Ulysse par son chien ...Argos dans Difficile liberté, tandis que le second se centre sur la transformation des compagnons d'Ulysse en pourceaux dans Récits d'humanisme. Ces deux philosophes contemporains inscrivent leur usage du texte antique dans les débats actuels portant sur la crise du sujet, ainsi que l'articulation de l'homme et de l'animal. En effet, les philosophes transforment ces épisodes en fables philosophiques qui rendent ces rencontres particulièrement signifiantes : avec Ulysse, elles refondent la personne en interrogeant d'un point de vue éthique les frontières séparant d'ordinaire l'homme de l'animal. Emmanuel Levinas and Michel Serres both comment and rewrite two episodes from Homer's Odyssey where Ulysses is confronted with an animal : the first concentrates in Difficile liberté – Difficult freedom on Argos' – Ulysses'dog – recognition of his master, while the latter focuses, in Récits d'humanisme, on the transformation of Ulysses'companions into swine. Both these contemporary philosophers insert their use of the texts from Antiquity into contemporary debates regarding the crisis of the subject and the relationship between humanity and animality. Both the philosophers indeed transform these episodes into philosophical tales which render these encounters particularly significant : they use Ulysses to renew the foundation of personhood by exploring from an ethical point of view the usual frontiers between man and animal.
The Hubble Ultra Deep Field source JD2 presented in Mobasher et al. is an unusual galaxy that is very faint at all wavelengths shortward of 1.1 mu m. Photometric redshift fits to data between 0.4 and ...8 mu m yield a significant probability that It is an extremely massive galaxy at z similar to 6.5. In this paper we present new photometry at 16 and 22 mu m from Spitzer Infrared Spectrograph (IRS) peak-up imaging of the Great Observatories Origins Deep Survey (GOODS) fields. We find that the spectral energy distribution shows a factor of similar to 4 rise in flux density between the 16 and 22 mu m bandpass, which is most likely due to the entrance of polycyclic aromatic hydrocarbon emission features into the 22 and 24 mu m passbands. The flux ratio between these bandpasses can be best fit by a z = 1.7 luminous infrared galaxy with a bolometric luminosity of (2-6) x 10 super(11) L unk corresponding to a star formation rate of 80 M unk yr super(-1). The predicted flux density values at other longer wavelengths are below the detection limits of current instrumentation, but such sources could potentially be detected in tensed submillimeter surveys. Reevaluation of the optical/near-infrared photometry continues to favor z > 6 photometric redshift solutions, but we argue that the consistency of the multiwavelength parameters of this galaxy with other dusty starbursts favor the z similar to 2 mid-infrared photometric redshift. The data presented here provide evidence that optically undetected near-infrared sources that are detected at 24 mu m are most likely dusty, starburst galaxies at a redshift of z similar to 2 with stellar masses >10 super(10) M unk.
We report the discovery of two peculiar galaxies infalling into the lensing clusters of galaxies Abell 1689 (z~ 0.18) and 2667 (z~ 0.23). Hubble Space Telescope images show extraordinary trails ...composed by blue bright knots and stellar streams associated with both these systems, an ~L* and ~0.1L* galaxy. Under the combined action of tidal interaction with the cluster potential and of ram pressure by the intra-cluster medium the morphologies and star formation histories of these two galaxies are strongly perturbed. While in the massive system tidal interactions are the dominant effect and are able to produce a sinking of gas towards the galaxy center triggering a strong burst of star formation and changing galaxy's morphology, in the smaller galaxy the effects of gravitation are reduced by ram pressure stripping which blows away the neutral hydrogen from the galactic disk, quenching the star formation activity and transforming a gas rich late type spiral into quiescent disk dominated early type system. This result is a new additional evidence that galaxy mass represents the main driver of galaxy evolution, even during their dive into the harsh cluster environment and can give additional insights on the origin of S0s and dwarf cluster galaxies.
A sample of distant ($z>0.4$) luminous infrared galaxies (LIRGs) selected from ISOCAM deep survey fields (CFRS, UDSR, UDSF) have been studied on the basis of their high-quality optical spectra from ...VLT/FORS2 (R=5Å). Robust estimates of dust extinction can be considered via the energy balance between the infrared and H$\beta$ luminosities, after correcting the underlying Balmer absorption properly. Oxygen abundances 12+log(O/H) in the interstellar medium of the sample galaxies estimated from the “strong-line” method show a range from 8.36 to 8.93, with a median value of 8.67, which is 0.5 lower than that of local bright disks (i.e. $L^*$) at the given magnitude. The timescale to double the stellar masses of such LIRGs can be very short, 0.1-1 Gyr. A significant fraction of distant large disks are indeed LIRGs. Such massive disks could have formed $\sim50$% of their metals and stellar masses since $z\sim1$.
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 z to decipher when and to what extent a secular evolution is sufficient to explain the star formation history in galaxies. Methods. We selected star-forming galaxies at $z=0$ and at $z=0.7$ in IR and in UV to have access to all the recent star formation. We focused on galaxies with a stellar mass ranging between 1010 and $10^{11}~M_{\odot}$ for which the results are not biased by the selections. We compared the data to chemical evolution models developed for spiral galaxies and originally built to reproduce the main characteristics of the Milky Way and nearby spirals without fine-tuning them for the present analysis. Results. We find a shallow decrease in the specific star formation rate (SSFR) when the stellar mass increases. The evolution of the SSFR characterizing both UV and IR selected galaxies from $z=0$ to $z=0.7$ is consistent with the models built to reproduce the present spiral galaxies. There is no need to strongly modify of the physical conditions in galaxies to explain the average evolution of their star formation from $z=0$ to $z=0.7$. We use the models to predict the evolution of the star formation rate and the metallicity on a wider range of redshift and we compare these predictions with the results of semi-analytical models.
PDF
