We present measurements of the Hubble diagram for 103 Type Ia supernovae (SNe) with redshifts 0.04 < z < 0.42, discovered during the first season (Fall 2005) of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. These data fill in the redshift "desert" between low-and high-redshift SN Ia surveys. Within the framework of the mlcs2k2 light-curve fitting method, we use the SDSS-II SN sample to infer the mean reddening parameter for host galaxies, R V = 2.18 ± 0.14 stat ± 0.48 syst , and find that the intrinsic distribution of host-galaxy extinction is well fitted by an exponential function, P (A V) = exp(−A V /τ V), with τ V = 0.334 ± 0.088 mag. We combine the SDSS-II measurements with new distance estimates for published SN data from the ESSENCE survey, the Supernova Legacy Survey (SNLS), the Hubble Space Telescope (HST), and a compilation of Nearby SN Ia measurements. A new feature in our analysis is the use of detailed Monte Carlo simulations of all surveys to account for selection biases, including those from spectroscopic targeting. Combining the SN Hubble diagram with measurements of baryon acoustic oscillations from the SDSS Luminous Red Galaxy sample and with cosmic microwave background temperature anisotropy measurements from the Wilkinson Microwave Anisotropy Probe, we estimate the cosmological parameters w and Ω M , assuming a spatially flat cosmological model (FwCDM) with constant dark energy equation of state parameter, w. We also consider constraints upon Ω M and Ω Λ for a cosmological constant model (ΛCDM) with w = −1 and non-zero spatial curvature. For the FwCDM model and the combined sample of 288 SNe Ia,
We present a measurement of the evolution of the stellar mass function (MF) of galaxies and the evolution of the total stellar mass density at 0 < z < 5, extending previous measurements to higher redshift and fainter magnitudes (and lower masses). We use deep multicolor data in the Fors Deep Field (FDF; I-selected reaching I AB ∼ 26.8) and the GOODS-S/CDFS region (K-selected reaching K AB ∼ 25.4) to estimate stellar masses based on fits to composite stellar population models for 5557 and 3367 sources, respectively. The MF of objects from the K-selected GOODS-S sample is very similar to that of the I-selected FDF down to the completeness limit of the GOODS-S sample. Near-IR selected surveys hence detect the more massive objects of the same principal population as do I-selected surveys. We find that the most massive galaxies harbor the oldest stellar populations at all redshifts. At low z, our MF follows the local MF very well, extending the local MF down by a decade to 10 8 M ⊙ . Furthermore, the faint end slope is consistent with the local value of α ∼ 1.1 at least up to z ∼ 1.5. Our MF also agrees very well with the MUNICS and K20 results at z 2. The MF seems to evolve in a regular way at least up to z ∼ 2 with the normalization decreasing by 50% to z = 1 and by 70% to z = 2. Objects with M > 10 10 M ⊙ which are the likely progenitors of todays L > L * galaxies are found in much smaller numbers above z ∼ 2. However, we note that massive galaxies with M > 10 11 M ⊙ are present even to the largest redshift we probe. Beyond z ∼ 2 the evolution of the mass function becomes more rapid. We find that the total stellar mass density at z = 1 is 50% of the local value. At z = 2, 25% of the local mass density is assembled, and at z = 3 and z = 5 we find that at least 15% and 5% of the mass in stars is in place, respectively. The number density of galaxies with M > 10 11 M ⊙ evolves very similarly to the evolution at lower masses. It decreases by 0.4 dex to z ∼ 1, by 0.6 dex to z ∼ 2, and by 1 dex to z ∼ 4.
The Sloan Digital Sky Survey-II (SDSS-II) has embarked on a multi-year project to identify and measure light curves for intermediate-redshift (0.05 < z < 0.35) Type Ia supernovae (SNe Ia) using repeated five-band (ugriz) imaging over an area of 300 sq. deg. The survey region is a stripe 2.5• wide centered on the celestial equator in the Southern Galactic Cap that has been imaged numerous times in earlier years, enabling construction of a deep reference image for the discovery of new objects. Supernova imaging observations are being acquired between September 1 and November 30 of 2005-7. During the first two seasons, each region was imaged on average every five nights. Spectroscopic follow-up observations to determine supernova type and redshift are carried out on a large number of telescopes. In its first two three-month seasons, the survey has discovered and measured light curves for 327 spectroscopically confirmed SNe Ia, 30 probable SNe Ia, 14 confirmed SNe Ib/c, 32 confirmed SNe II, plus a large number of photometrically identified SNe Ia, 94 of which have host-galaxy spectra taken so far. This paper provides an overview of the project and briefly describes the observations completed during the first two seasons of operation.
We present a measurement of the evolution of the stellar mass function in four redshift bins at 0:4 < z <1:2, using a sample of more than 5000 K-selected galaxies drawn from the MUNICS (Munich Near-Infrared Cluster Survey) data set. Our data cover the stellar mass range 10 10 h À2 M M 10 12 h À2 M . We derive K-band mass-to-light ratios by fitting a grid of composite stellar population models of varying star formation history, age, and dust extinction to BVRIJK photometry. We discuss the evolution of the average mass-to-light ratio as a function of galaxy stellar mass in the K and B bands. We compare our stellar mass function at z > 0 to estimates obtained similarly at z ¼ 0. We find that the mass-to-light ratios in the K band decline with redshift. This decline is similar for all stellar masses above 10 10 h À2 M . Lower mass galaxies have lower mass-to-light ratios at all redshifts. The stellar mass function evolves significantly to z ¼ 1:2. The total normalization decreases by a factor of $2, the characteristic mass (the knee) shifts toward lower masses, and the bright end therefore steepens with redshift. The amount of number density evolution is a strong function of stellar mass, with more massive systems showing faster evolution than less massive systems. We discuss the total stellar mass density of the universe and compare our results to the values from the literature at both lower and higher redshifts. We find that the stellar mass density at z $ 1 is roughly 50% of the local value. Our results imply that the mass assembly of galaxies continues well after z $ 1. Our data favor a scenario in which the growth of the most massive galaxies is dominated by accretion and merging rather than star formation, which plays a larger role in the growth of less massive systems.
We study the escape of Lyα photons from Lyα emitting galaxies (LAEs) and the overall galaxy population using a sample of 99 LAEs at 1.9 < z < 3.8 detected through integral-field spectroscopy of blank fields by the HETDEX Pilot Survey. For 89 LAEs with broad-band counterparts we measure UV luminosities and UV slopes, and estimate E(B − V ) under the assumption of a constant intrinsic UV slope for LAEs. These quantities are used to estimate dust-corrected star formation rates (SF R). Comparison between the observed Lyα luminosity and -2 -that predicted by the dust-corrected SF R yields the Lyα escape fraction. We also measure the Lyα luminosity function and luminosity density (ρ Lyα ) at 2 < z < 4. Using this and other measurements from the literature at 0.3 < z < 7.7 we trace the redshift evolution of ρ Lyα . We compare it to the expectations from the starformation history of the universe and characterize the evolution of the Lyα escape fraction of galaxies. LAEs at 2 < z < 4 selected down to a luminosity limit of L(Lyα) > 3 − 6 × 10 42 erg s −1 (0.25 to 0.5 L * ), have a mean E(B − V ) = 0.13 ± 0.01, implying an attenuation of ∼ 70% in the UV. They show a median UV uncorrected SF R = 11 M ⊙ yr −1 , dust-corrected SF R = 34 M ⊙ yr −1 , and Lyα equivalent widths (EW s) which are consistent with normal stellar populations. We measure a median Lyα escape fraction of 29%, with a large scatter and values ranging from a few percent to 100%. The Lyα escape fraction in LAEs correlates with E(B − V ) in a way that is expected if Lyα photons suffer from similar amounts of dust extinction as UV continuum photons. This result implies that a strong enhancement of the Lyα EW with dust, due to a clumpy multi-phase ISM, is not a common process in LAEs at these redshifts. It also suggests that while in other galaxies Lyα can be preferentially quenched by dust due to its scattering nature, this is not the case in LAEs. We find no evolution in the average dust content and Lyα escape fraction of LAEs from z ∼ 4 to 2. We see hints of a drop in the number density of LAEs from z ∼ 4 to 2 in the redshift distribution and the Lyα luminosity function, although larger samples are required to confirm this. The mean Lyα escape fraction of the overall galaxy population decreases significantly from z ∼ 6 to z ∼ 2. Our results point towards a scenario in which star-forming galaxies build up significant amounts of dust in their ISM between z ∼ 6 and 2, reducing their Lyα escape fraction, with LAE selection preferentially detecting galaxies which have the highest escape fractions given their dust content. The fact that a large escape of Lyα photons is reached by z ∼ 6 implies that better constraints on this quantity at higher redshifts might detect re-ionization in a way that is uncoupled from the effects of dust.
Abstract. We use the very deep and homogeneous I-band selected dataset of the FORS Deep Field (FDF) to trace the evolution of the luminosity function over the redshift range 0.5 < z < 5.0. We show that the FDF I-band selection down to I AB = 26.8 misses of the order of 10% of the galaxies that would be detected in a K-band selected survey with magnitude limit K AB = 26.3 (like FIRES). Photometric redshifts for 5558 galaxies are estimated based on the photometry in 9 filters (U, B, Gunn g, R, I, SDSS z, J, K and a special filter centered at 834 nm). A comparison with 362 spectroscopic redshifts shows that the achieved accuracy of the photometric redshifts is ∆z/(z spec + 1) ≤ 0.03 with only ∼1% outliers. This allows us to derive luminosity functions with a reliability similar to spectroscopic surveys. In addition, the luminosity functions can be traced to objects of lower luminosity which generally are not accessible to spectroscopy. We investigate the evolution of the luminosity functions evaluated in the restframe UV (1500 Å and 2800 Å), u , B, and g bands. Comparison with results from the literature shows the reliability of the derived luminosity functions. Out to redshifts of z ∼ 2.5 the data are consistent with a slope of the luminosity function approximately constant with redshift, at a value of −1.07 ± 0.04 in the UV (1500 Å, 2800 Å) as well as u , and −1.25 ± 0.03 in the blue (g , B). We do not see evidence for a very steep slope (α ≤ −1.6) in the UV at z ∼ 3.0 and z ∼ 4.0 favoured by other authors. There may be a tendency for the faint-end slope to become shallower with increasing redshift but the effect is marginal. We find a brightening of M * and a decrease of φ * with redshift for all analyzed wavelengths. The effect is systematic and much stronger than what can be expected to be caused by cosmic variance seen in the FDF. The evolution of M * and φ * from z = 0 to z = 5 is well described by the simple approximations Mfor M * and φ * . The evolution is very pronounced at shorter wavelengths (a = −2.19, and b = −1.76 for 1500 Å rest wavelength) and decreases systematically with increasing wavelength, but is also clearly visible at the longest wavelength investigated here (a = −1.08, and b = −1.29 for g ). Finally we show a comparison with semi-analytical galaxy formation models.Key words. galaxies: luminosity function, mass function -galaxy: fundamental parameters -galaxies: high-redshiftgalaxies: distances and redshifts -galaxies: evolution
We present new optical long-slit data along six position angles of the bulge region of M 31. We derive accurate stellar and gas kinematics reaching 5 arcmin from the center, where the disk light contribution is always less than 30%, and out to 8 arcmin along the major axis, where the disk provides 55% of the total light. We show that the velocity dispersions of McElroy (1983) are severely underestimated (by up to 50 km s −1 ). As a consequence, previous dynamical models have underestimated the stellar mass of M 31's bulge by a factor of 2. As a further consequence, the light-weighted velocity dispersion of the galaxy grows to 166 km s −1 and to 170 km s −1 if rotation is also taken into account, thus reducing the discrepancy between the predicted and measured mass of the black hole at the center of M 31 from a factor of 3 to a factor of 2. The kinematic position angle varies with distance, pointing to triaxiality, but a quantitative conclusion can be reached only after simultaneous proper dynamical modeling of the bulge and disk components is performed. We detect gas counterrotation near the bulge minor axis. We measure eight emission-corrected Lick indices. They are approximately constant on circles. Using simple stellar population models we derive the age, metallicity and α-element overabundance profiles. Except for the region in the inner arcsecs of the galaxy, the bulge of M 31 is uniformly old (≥12 Gyr, with many best-fit ages at the model grid limit of 15 Gyr), slightly α-elements overabundant ([α/Fe] ≈ 0.2) and of solar metallicity, in agreement with studies of the resolved stellar components. The predicted u − g, g − r and r − i Sloan color profiles match the dust-corrected observations reasonably well, within the known limitations of current simple stellar population models. The stellar populations have approximately radially constant mass-to-light ratios (M/L R ≈ 4−4.5 M /L for a Kroupa IMF), which is in agreement with the stellar dynamical estimates based on our new velocity dispersions. In the inner arcsecs the luminosity-weighted age drops to 4-8 Gyr, while the metallicity increases to above three times the solar value. Starting from 6 arcmin from the center along the major axis, the mean age drops to ≤8 Gyr with slight supersolar metallicity (≈+0.1 dex) and α-element overabundance (≈+0.2 dex) for a mass-to-light ratio M/L R ≤ 3 M /L . Diagnostic diagrams based on the [OIII]/Hβ and [NI]/Hβ emission line equivalent widths (EWs) ratios indicate that the gas is ionized by shocks outside 10 arcsec, but an AGN-like ionizing source could be present near the center. We speculate that a gas-rich minor merger happened some 100 Myr ago, causing the observed minor axis gas counterrotation, the recent star formation event and possibly some nuclear activity.
We present the morphological analysis based on HST-NIC2 (0.075 arcsec pixel −1 ) images in the F160W filter of a sample of nine massive field (>10 11 M ) galaxies spectroscopically classified as early-types at 1.2 < z < 1.7. Our analysis shows that all of them are bulgedominated systems. In particular, six of them are well fitted by a de Vaucouleurs profile (n = 4) suggesting that they can be considered pure elliptical galaxies. The remaining three galaxies are better fitted by a Sérsic profile with index 1.9 < n fit < 2.3 suggesting that a disc-like component could contribute up to 30 per cent to the total light of these galaxies. We derived the effective radius R e and the mean surface brightness (SB) μ e within R e of our galaxies and we compared them with those of early-types at lower redshifts. We find that the SB μ e of our galaxies should get fainter by 2.5 mag from z ∼ 1.5 to ∼0 to match the SB of the local ellipticals with comparable R e , that is, the local Kormendy relation. Luminosity evolution without morphological changes can only explain half of this effect, as the maximum dimming expected for an elliptical galaxy is ∼1.6 mag in this redshift range. Thus, other parameters, possibly structural, may undergo evolution and play an important role in reconciling models and observations. Hypothesizing an evolution of the effective radius of galaxies we find that R e should increase by a factor of 1.5 from z ∼ 1.5 to ∼0.
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