On the dependence between UV luminosity and Lyman-alpha equivalent width in high redshift galaxies

We show that with the simple assumption of no correlation between the Ly-alpha equivalent width and the UV luminosity of a galaxy, the observed distribution of high redshift galaxies in an equivalent width - absolute UV magnitude plane can be reproduced. We further show that there is no dependence between Ly-alpha equivalent width and Ly-alpha luminosity in a sample of Ly-alpha emitters. The test was expanded to Lyman-break galaxies and again no dependence was found. Simultaneously, we show that a recently proposed lack of large equivalent width, UV bright galaxies (Ando et al. 2006) can be explained by a simple observational effect, based on too small survey volumes.Comment: 7 pages, 3 figures, 2 tables, accepted in MNRA

Narrow band imaging in [OIII] and Halpha to search for ICPNe in the Virgo cluster

We have identified intracluster planetary nebulae in a Virgo cluster core field by imaging with the Subaru Suprime-Cam through two narrow band filters centered at the redshifted wavelengths of the [OIII] $\lambda=5007$ \AA and the H$\alpha$ $\lambda = 6563$ \AA lines; broad-band images in V and R were acquired to check for emission in the adjacent continuum. Emission line objects in Virgo are then selected from the two-color diagram ([OIII] -- Halpha) vs. ([OIII] -- (V+R)), which is calibrated using PNe in M84 (Jacoby et al. 1990). Using both [OIII] and Halpha allows us to distinguish bona-fide planetary nebulae from high redshift emission-line galaxies at the bright end of the [OIII] luminosity function. Spectroscopic observations of a subsample of these objects were made at the TNG and at the VLT, in a region around M84 and in an intracluster field respectively. The observations confirm the efficiency of the combined [OIII]+H$\alpha$ imaging to identify true PNe. We also obtained the first spectrum of an intracluster PN which shows the [OIII] doublet with S/N > 10 and its Halpha emission. From the results based on the spectroscopic follow-up, we derive a lower limit to the fraction of the Virgo cluster light contributed by the intracluster stars at the surveyed position in the cluster core: it amounts to 10%.Comment: 32 pages,11 figures, in press on AJ, February 200

The nature of z ~ 2.3 Lyman-alpha emitters

We study the multi-wavelength properties of a set of 171 Ly-alpha emitting candidates at redshift z = 2.25 found in the COSMOS field, with the aim of understanding the underlying stellar populations in the galaxies. We especially seek to understand what the dust contents, ages and stellar masses of the galaxies are, and how they relate to similar properties of Ly-alpha emitters at other redshifts. The candidates here are shown to have different properties from those of Ly-alpha emitters found at higher redshift, by fitting the spectral energy distributions (SEDs) using a Monte-Carlo Markov-Chain technique and including nebular emission in the spectra. The stellar masses, and possibly the dust contents, are higher, with stellar masses in the range log M_* = 8.5 - 11.0 M_sun and A_V = 0.0 - 2.5 mag. Young population ages are well constrained, but the ages of older populations are typically unconstrained. In 15% of the galaxies only a single, young population of stars is observed. We show that the Ly-alpha fluxes of the best fit galaxies are correlated with their dust properties, with higher dust extinction in Ly-alpha faint galaxies. Testing for whether results derived from a light-weighted stack of objects correlate to those found when fitting individual objects we see that stellar masses are robust to stacking, but ages and especially dust extinctions are derived incorrectly from stacks. We conclude that the stellar properties of Ly-alpha emitters at z = 2.25 are different from those at higher redshift and that they are diverse. Ly-alpha selection appears to be tracing systematically different galaxies at different redshifts.Comment: 15 pages, 11 figures, 8 tables, accepted in A&A. Table 6 available in full from the author

Spectroscopy of luminous z>7 galaxy candidates and sources of contamination in z>7 galaxy searches

We present three bright z+ dropout candidates selected from deep Near-Infrared (NIR) imaging of the COSMOS 2 square degree field. All three objects match the 0.8-8um colors of other published z>7 candidates but are three magnitudes brighter, facilitating further study. Deep spectroscopy of two of the candidates covering 0.64-1.02um with Keck-DEIMOS and all three covering 0.94-1.10um and 1.52-1.80um with Keck-NIRSPEC detects weak spectral features tentatively identified as Ly-alpha at z=6.95 and z=7.69 in two of the objects. The third object is placed at z~1.6 based on a 24um and weak optical detection. A comparison with the spectral energy distributions of known z<7 galaxies, including objects with strong spectral lines, large extinction, and large systematic uncertainties in the photometry yields no objects with similar colors. However, the lambda>1um properties of all three objects can be matched to optically detected sources with photometric redshifts at z~1.8, so the non-detection in the i+ and z+ bands are the primary factors which favors a z>7 solution. If any of these objects are at z~7 the bright end of the luminosity function is significantly higher at z>7 than suggested by previous studies, but consistent within the statistical uncertainty and the dark matter halo distribution. If these objects are at low redshift, the Lyman-Break selection must be contaminated by a previously unknown population of low redshift objects with very strong breaks in their broad band spectral energy distributions and blue NIR colors. The implications of this result on luminosity function evolution at high redshift is discussed. We show that the primary limitation of z>7 galaxy searches with broad filters is the depth of the available optical data.Comment: 15 Pages, 15 figures, accepted to Ap

Stellar properties of z ~ 1 Lyman-break galaxies from ACS slitless grism spectra

Lyman-break galaxies are now regularly found in the high redshift Universe by searching for the break in the galaxy spectrum caused by the Lyman-limit redshifted into the optical or even near-IR. At lower redshift, this break is covered by the GALEX UV channels and small samples of z ~ 1 LBGs have been presented in the literature. Here we give results from fitting the spectral energy distributions of a small sub-set of low redshift LBGs and demonstrate the advantage of including photometric points derived from HST ACS slitless grism observations. The results show these galaxies to have very young, star forming populations, while still being massive and dusty. LBGs at low and high redshift show remarkable similarities in their properties, indicating that the LBG selection method picks similar galaxies throughout the Universe.Comment: 7 pages, 3 figures, 2 tables, accepted in A&

Organic Anion Transporter 5 (Oat5) Urinary Excretion Is a Specific Biomarker of Kidney Injury: Evaluation of Urinary Excretion of Exosomal Oat5 after N-Acetylcysteine Prevention of Cisplatin Induced Nephrotoxicity

Cisplatin is a commonly used chemotherapeutic agent. Its main side-effect is nephrotoxicity. It was reported that the organic anion transporter 5 (Oat5) urinary excretion is elevated, implying renal perturbation, when no modifications of traditional markers of renal damage are still observed in cisplatin-induced acute kidney injury (AKI). It was also demonstrated that Oat5 is excreted in urine by the exosomal pathway. This study was designated to demonstrate the specific response of the urinary excretion of exosomal Oat5 to kidney injury independently of other cisplatin toxic effects, in order to strengthen Oat5 urinary levels as a specific biomarker of AKI. To accomplish that aim, we evaluated if urinary excretion of exosomal Oat5 returns to its basal levels when cisplatin renal damage is prevented by the coadministration of the renoprotective compound N-acetylcysteine. Four days after cisplatin administration, AKI was induced in cisplatin-treated male Wistar rats (Cis group), as it was corroborated by increased urea and creatinine plasma levels. Tubular damage was also observed. In cotreated animals (Cis + NAC group), plasma urea and creatinine concentrations tended to return to their basal values, and tubular damage was improved. Urinary excretion of exosomal Oat5 was notably increased in the Cis group, but when renal injury was ameliorated by N-acetylcysteine coadministration, that increase was undetected. So, in this work we observed that urinary excretion of exosomal Oat5 was only increased if renal insult is produced, demonstrating its specificity as a renal injury biomarker.Fil: Bulacio, Romina Paula. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Anzai, Naohiko. Dokkyo Medical University; JapónFil: Ouchi, Motoshi. Dokkyo Medical University; JapónFil: Torres, Adriana Monica. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

The Interstellar Medium In Galaxies Seen A Billion Years After The Big Bang

Evolution in the measured rest frame ultraviolet spectral slope and ultraviolet to optical flux ratios indicate a rapid evolution in the dust obscuration of galaxies during the first 3 billion years of cosmic time (z>4). This evolution implies a change in the average interstellar medium properties, but the measurements are systematically uncertain due to untested assumptions, and the inability to measure heavily obscured regions of the galaxies. Previous attempts to directly measure the interstellar medium in normal galaxies at these redshifts have failed for a number of reasons with one notable exception. Here we report measurements of the [CII] gas and dust emission in 9 typical (~1-4L*) star-forming galaxies ~1 billon years after the big bang (z~5-6). We find these galaxies have >12x less thermal emission compared with similar systems ~2 billion years later, and enhanced [CII] emission relative to the far-infrared continuum, confirming a strong evolution in the interstellar medium properties in the early universe. The gas is distributed over scales of 1-8 kpc, and shows diverse dynamics within the sample. These results are consistent with early galaxies having significantly less dust than typical galaxies seen at z<3 and being comparable to local low-metallicity systems.Comment: Submitted to Nature, under review after referee report. 22 pages, 4 figures, 4 Extended Data Figures, 5 Extended Data table

The Star Formation Rate Density and Dust Attenuation Evolution over 12 Gyr with the VVDS Surveys

[Abridged] We investigate the global galaxy evolution over 12 Gyr (0.05<z<4.5), from the star formation rate density (SFRD), combining the VVDS Deep (17.5<=I<=24.0) and Ultra-Deep (23.00<=i<=24.75) surveys. We obtain a single homogeneous spectroscopic redshift sample, totalizing about 11000 galaxies. We estimate the rest-frame FUV luminosity function (LF) and luminosity density (LD), extract the dust attenuation of the FUV radiation using SED fitting, and derive the dust-corrected SFRD. We find a constant and flat faint-end slope alpha in the FUV LF at z1.7, we set alpha steepening with (1+z). The absolute magnitude M*_FUV brightens in the entire range 02 it is on average brighter than in the literature, while phi* is smaller. Our total LD shows a peak at z=2, present also when considering all sources of uncertainty. The SFRD history peaks as well at z=2. It rises by a factor of 6 during 2 Gyr (from z=4.5 to z=2), and then decreases by a factor of 12 during 10 Gyr down to z=0.05. This peak is mainly produced by a similar peak within the population of galaxies with -21.5<=M_FUV<=-19.5 mag. As times goes by, the total SFRD is dominated by fainter and fainter galaxies. The presence of a clear peak at z=2 and a fast rise at z>2 of the SFRD is compelling for models of galaxy formation. The mean dust attenuation A_FUV of the global galaxy population rises by 1 mag during 2 Gyr from z=4.5 to z=2, reaches its maximum at z=1 (A_FUV=2.2 mag), and then decreases by 1.1 mag during 7 Gyr down to z=0. The dust attenuation maximum is reached 2 Gyr after the SFRD peak, implying a contribution from the intermediate-mass stars to the dust production at z<2.Comment: 23 pages, 15 figures, accepted for publication in A&