S. Gallozzi

The GOODS-MUSIC sample: a multicolour catalog of near-IR selected galaxies in the GOODS-South field ,

Aims. We present a high quality multiwavelength (from 0.3 to 8.0 µm) catalog of the large and deep area in the GOODS Southern Field covered by the deep near-IR observations obtained with the ESO VLT. Methods. The catalog is entirely based on public data: in our analysis, we have included the F435W, F606W, F775W and F850LP ACS images, the JHKs VLT data, the Spitzer data provided by IRAC instrument (3.6, 4.5, 5.8 and 8.0 µm), and publicly available U-band data from the 2.2ESO and VLT-VIMOS. We describe in detail the procedures adopted to obtain this multiwavelength catalog. In particular, we developed a specific software for the accurate “PSF-matching” of space and ground-based images of different resolution and depth (ConvPhot), of which we analyse performances and limitations. We have included both z-selected, as well as Ks-selected objects, yielding a unique, self-consistent catalog. The largest fraction of the sample is 90% complete at z � 26 or Ks � 23.8 (AB scale). Finally, we cross-correlated our data with all the spectroscopic catalogs available to date, assigning a spectroscopic redshift to more than 1000 sources. Results. The final catalog is made up of 14 847 objects, at least 72 of which are known stars, 68 are AGNs, and 928 galaxies with spectroscopic redshift (668 galaxies with reliable redshift determination). We applied our photometric redshift code to this data set, and the comparison with the spectroscopic sample shows that the quality of the resulting photometric redshifts is excellent, with an average scatter of only 0.06. The full catalog, which we named GOODS-MUSIC (MUltiwavelength Southern Infrared Catalog), including the spectroscopic information, is made publicly available, together with the software specifically designed to this end.

Star formation and mass assembly in high redshift galaxies

Aims. The goal of this work is to infer the star formation properties and the mass assembly process of high redshift (0.3 ≤ z 0.3, the star formation rate is correlated well with stellar mass, and this relationship seems to steepen with redshift if one relies on IR-based estimates of the SFR; b) the contribution to the global SFRD by massive galaxies increases with redshift up to � 2.5, more rapidly than for galaxies of lower mass, but appears to flatten at higher z; c) despite this increase, the most important contributors to the SFRD at any z are galaxies of about, or immediately lower than, the characteristic stellar mass;

The evolving slope of the stellar mass function at 0.6 ≤ z < 4.5 from deep WFC3 data

We used Early Release Science (ERS) observations taken with the Wide Field Camera 3 (WFC3) in the GOODS-S field to study the galaxy stellar mass function (GSMF) at 0.6 ≤ z 2. However, we confirm that there appears to be an excess of integrated star formation with respect to the SMD at z < 2, by a factor of ∼2−3. Our comparison of the observations with theoretical predictions shows that the models forecast a greater abundance of low mass galaxies, at least up to z ∼ 3, as well as a dearth of massive galaxies at z ∼ 4 with respect to the data, and that the predicted SMD is generally overestimated at z < 2.

A comparison of LBGs, DRGs, and BzK galaxies: their contribution to the stellar mass density in the GOODS-MUSIC sample

Context. The classification scheme for high redshift galaxies is complex at the present time, with simple colour selection criteria (i.e. EROs, IEROs, LBGs, DRGs, BzKs), resulting in ill-defined properties regarding stellar mass and star formation rate for these distant galaxies. Aims. The goal of this work is to investigate the properties of different classes of high-z galaxies, focusing in particular on the Stellar Masses of LBGs, DRGs and BzKs, in order to derive their contribution to the total mass budget of the distant Universe. Methods. We have used the GOODS-MUSIC catalog, containing ∼3000 Ks–selected (∼10000 z–selected) galaxies with multiwavelength coverage extending from the U band to the Spitzer 8μm band, with spectroscopic or accurate photometric redshifts. We have selected samples of BM/BX/LBGs, DRGs and BzK galaxies, discussed the overlap and the limitations of these criteria, which can be overcome with a selection criterion based on physical parameters. We have then measured the stellar masses of these galaxies and computed the Stellar Mass Density (SMD) for the different samples up to redshift ≃ 4. Results. We show that the BzK-PE criterion is not optimal to select early type galaxies at the faint end. BzK-SF, on the other hand, is highly contaminated by passively evolving galaxies at red z − Ks colours. We find that LBGs and DRGs contribute almost equally to the global SMD at z ≥ 2 and in general that star forming galaxies form a substantial fraction of the universal SMD. Passively evolving galaxies show a strong negative density evolution from redshift 2 to 3, indicating that we are witnessing the epoch of mass assembly of such objects. Finally we find indications that pushing the selection to deeper magnitudes, the contribution of less massive DRGs could overcome that of LBGs. Deeper surveys, like the HUDF, are required to confirm this

Evidence for a fast evolution of the UV luminosity function beyond redshift 6 from a deep HAWK-I survey of the GOODS-S field.

Aims. We perform a deep search for galaxies in the redshift range 6.5�z�7.5, to measure the evolution of the number density of luminous galaxies in this redshift range and derive useful constraints on the evolution of their Luminosity Function. Methods. We present here the first results of an ESO Large Program, that exploits the unique combination of area and sensitivity provided in the near‐IR by the camera Hawk-I at the VLT. We have obtained two Hawk-I pointings on the GOODS South field for a total of�32 observing hours, covering�90 arcmin 2 . The images reach Y = 26.7 mags for the two fields. We have used public ACS images in the z band to select z-dropout galaxies with the colour criteria Z− Y �1, Y− J < 1.5 and Y− K < 2. The other public data in the UBVRIJK bands are used to reject possible low redshift interlopers. The output has been compared with extensive Monte Carlo simulations to quantify the observational effects of our selection criteria as well as the effects of photometric errors.

The bright end of the z ~ 7 UV luminosity function from a wide and deep HAWK-I survey

Aims. We perform a deep search for galaxies in the redshift range 6: 5�z�7: 5, to measure the evolution of the number density of luminous galaxies in this redshift range and derive useful constraints on the evolution of their luminosity function. Methods. We present here the second half of an ESO Large Programme, which exploits the unique combination of area and sensitivity provided in the near‐IR by the camera Hawk-I at the VLT. We have obtained�30 observing hours with Hawk-I in the Y-band of two high galactic latitude fields. We combined the Y-band data with deep J and K Hawk-I observations, and with FORS1/FORS2 U, B, V, R, I, and Z observations to select z-drop galaxies having Z− Y> 1, no optical detection and flat Y− J and Y− K colour terms. Results. We detect 8 high-quality candidates in the magnitude range Y = 25: 5− 26: 5 that we add to the z-drop candidates selected in two Hawk-I pointings over the GOODS-South field. We use thi s full sample of 15 objects found in�161 arcmin 2 of our survey to constrain the average physical properties and the evolut ion of the number density of z �7 LBGs. A stacking analysis yields a

A LOW ESCAPE FRACTION OF IONIZING PHOTONS OF L > L* LYMAN BREAK GALAXIES AT z = 3.3

We present an upper limit for the relative escape fraction (f rel esc) of ionizing radiation at z ~ 3.3 using a sample of 11 Lyman break galaxies (LBGs) with deep imaging in the U band obtained with the Large Binocular Camera, mounted on the prime focus of the Large Binocular Telescope. We selected 11 LBGs with secure redshifts in the range 3.27 < z < 3.35, from three independent fields. We stacked the images of our sources in the R and U bands, which correspond to an effective rest-frame wavelength of 1500 A and 900 A, respectively, obtaining a limit in the U band image of ≥30.7 mag (AB) at 1σ. We derive a 1σ upper limit of f rel esc ~ 5%, which is one of the lowest values found in the literature so far at z ~ 3.3. Assuming that the upper limit for the escape fraction that we derived from our sample holds for all galaxies at this redshift, the hydrogen ionization rate that we obtain (Γ–12 < 0.3 s–1) is not enough to keep the intergalactic medium ionized and a substantial contribution to the UV background by faint active galactic nuclei is required. Since our sample is clearly still limited in size, larger z ~ 3 LBG samples at similar or even greater depths are necessary to confirm these results on a more firm statistical basis.

Physical properties of z ~ 4 LBGs: differences between galaxies with and without Lyα emission

Aims. We analysed the physical properties of z ∼ 4 Lyman Break Galaxies observed in the GOODS-S survey, in order to investigate possible differences between galaxies where the Lyα is present in emission, and those where the line is absent or in absorption. Methods. The objects were selected from their optical color and then spectroscopically confirmed by Vanzella et al. (2005). From the public spectra we assessed the nature of the Lyα emission and divided the sample into galaxies with Lyα in emission and objects without a Lyα line (i.e. either absent or in absorption). We then used complete photometry, from U band to mid-infrared from the GOODS-MUSIC database, to study the observational properties of the galaxies, such as UV spectral slopes and optical to mid-infrared colors, and the possible differences between the two samples. Lastly, we used standard spectral fitting techniques to determine the physical properties of the galaxies, such as total stellar mass, stellar ages and so on, and again we looked at the possible differences between the two samples. Results. Our results indicate that LBG with Lyα in emission are on average a much younger and less massive population than the LBGs without Lyα emission. Both populations are forming stars very actively and are relatively dust free, although those with line emission seem to be even less dusty on average. We briefly discuss these results in the context of recent models for the evolution of Lyman break galaxies and Lyα emitters.

The clustering evolution of distant red galaxies in the GOODS-MUSIC sample

Aims. We study the clustering properties of Distant Red Galaxies (DRGs) to test whether they are the progenitors of local massive galaxies. Methods. We use the GOODS-MUSIC sample, a catalog of ∼3000 Ks-selected galaxies based on VLT and HST observation of the GOODS-South field with extended multi-wavelength coverage (from 0.3 to 8 μm) and accurate estimates of the photometric redshifts to select 179 DRGs with J - Ks > 1.3 in an area of 135 sq. arcmin. Results. We first show that the J - Ks > 1.3 criterion selects a rather heterogeneous sample of galaxies, going from the targeted high-redshift luminous evolved systems, to a significant fraction of lower redshift (1 < z < 2) and less luminous dusty starbursts. These low-redshift DRGs are significantly less clustered than higher-z DRGs. With the aid of extreme and simplified theoretical models of clustering evolution, we show that it is unlikely that the two samples are drawn from the same population observed at two different stages of evolution. Conclusions. High-z DRGs likely represent the progenitors of the more massive and more luminous galaxies in the local Universe and might mark the regions that will later evolve into structures of intermediate mass, like groups or small galaxy clusters. Low-z DRGs, on the other hand, will likely evolve into slightly less massive field galaxies.

The end of the white dwarf cooling sequence in M 67

In this paper, we present for the first time a proper-motion-selected white dwarf (WD) sample of the old Galactic open cluster M 67, down to the bottom of the WD cooling sequence (CS). The color-magnitude diagram is based on data collected with the LBC-Blue camera at the prime-focus of LBT. As first epoch data, we used CFHT-archive images collected 10 years before LBC data. We measured proper motions of all the identified sources. Proper motions are then used to separate foreground and background objects from the cluster stars, including WDs. Finally, the field-object cleaned WD CS in the V vs. B-I color-magnitude diagram is compared with the models. We confirm that the age derived from the location of the bottom of the WD CS is consistent with the turn off age.