L. Galbany

Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples

Aims. We present cosmological constraints from a joint analysis of type Ia supernova (SN Ia) observations obtained by the SDSS-II and SNLS collaborations. The dataset includes several low-redshift samples (z< 0.1), all three seasons from the SDSS-II (0.05 <z< 0.4), and three years from SNLS (0.2 <z< 1), and it totals 740 spectroscopically confirmed type Ia supernovae with high-quality light curves. Methods. We followed the methods and assumptions of the SNLS three-year data analysis except for the following important improvements: 1) the addition of the full SDSS-II spectroscopically-confirmed SN Ia sample in both the training of the SALT2 light-curve model and in the Hubble diagram analysis (374 SNe); 2) intercalibration of the SNLS and SDSS surveys and reduced systematic uncertainties in the photometric calibration, performed blindly with respect to the cosmology analysis; and 3) a thorough investigation of systematic errors associated with the SALT2 modeling of SN Ia light curves. Results. We produce recalibrated SN Ia light curves and associated distances for the SDSS-II and SNLS samples. The large SDSS-II sample provides an effective, independent, low-z anchor for the Hubble diagram and reduces the systematic error from calibration systematics in the low-z SN sample. For a flat ΛCDM cosmology, we find Ωm =0.295 ± 0.034 (stat+sys), a value consistent with the most recent cosmic microwave background (CMB) measurement from the Planck and WMAP experiments. Our result is 1.8σ (stat+sys) different than the previously published result of SNLS three-year data. The change is due primarily to improvements in the SNLS photometric calibration. When combined with CMB constraints, we measure a constant dark-energy equation of state parameter w =−1.018 ± 0.057 (stat+sys) for a flat universe. Adding baryon acoustic oscillation distance measurements gives similar constraints: w =−1.027 ± 0.055. Our supernova measurements provide the most stringent constraints to date on the nature of dark energy.

The CALIFA survey across the Hubble sequence: Spatially resolved stellar population properties in galaxies

Various different physical processes contribute to the star formation and stellar mass assembly histories of galaxies. One important approach to understanding the significance of these different processes on galaxy evolution is the study of the stellar population content of todays galaxies in a spatially resolved manner. The aim of this paper is to characterize in detail the radial structure of stellar population properties of galaxies in the nearby universe, based on a uniquely large galaxy sample, considering the quality and coverage of the data. The sample under study was drawn from the CALIFA survey and contains 300 galaxies observed with integral field spectroscopy. These cover a wide range of Hubble types, from spheroids to spiral galaxies, while stellar masses range from M_* ∼ 10^9 to 7 x 10^11 M_⨀. We apply the fossil record method based on spectral synthesis techniques to recover the following physical properties for each spatial resolution element in our target galaxies: the stellar mass surface density (μ_*), stellar extinction (A_V), light-weighted and mass-weighted ages ( _L, _M), and mass-weighted metallicity ( _M). To study mean trends with overall galaxy properties, the individual radial profiles are stacked in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc, and Sd). We confirm that more massive galaxies are more compact, older, more metal rich, and less reddened by dust. Additionally, we find that these trends are preserved spatially with the radial distance to the nucleus. Deviations from these relations appear correlated with Hubble type: earlier types are more compact, older, and more metal rich for a given M-star, which is evidence that quenching is related to morphology, but not driven by mass. Negative gradients of _L are consistent with an inside-out growth of galaxies, with the largest _L gradients in Sb-Sbc galaxies. Further, the mean stellar ages of disks and bulges are correlated and with disks covering a wider range of ages, and late-type spirals hosting younger disks. However, age gradients are only mildly negative or flat beyond R∼2 HLR (half light radius), indicating that star formation is more uniformly distributed or that stellar migration is important at these distances. The gradients in stellar mass surface density depend mostly on stellar mass, in the sense that more massive galaxies are more centrally concentrated. Whatever sets the concentration indices of galaxies obviously depends less on quenching/morphology than on the depth of the potential well. There is a secondary correlation in the sense that at the same M_* early-type galaxies have steeper gradients. The μ_* gradients outside 1 HLR show no dependence on Hubble type. We find mildly negative _M gradients, which are shallower than predicted from models of galaxy evolution in isolation. In general, metallicity gradients depend on stellar mass, and less on morphology, hinting that metallicity is affected by both - the depth of the potential well and morphology/quenching. Thus, the largest _M gradients occur in Milky Way-like Sb-Sbc galaxies, and are similar to those measured above the Galactic disk. Sc spirals show flatter _M gradients, possibly indicating a larger contribution from secular evolution in disks. The galaxies from the sample have decreasing-outward stellar extinction; all spirals show similar radial profiles, independent from the stellar mass, but redder than E and S0. Overall, we conclude that quenching processes act in manners that are independent of mass, while metallicity and galaxy structure are influenced by mass-dependent processes.

On the diversity of superluminous supernovae: ejected mass as the dominant factor

We assemble a sample of 24 hydrogen-poor superluminous supernovae (SLSNe). Parameterizing the light-curve shape through rise and decline time-scales shows that the two are highly correlated. Magnetar-powered models can reproduce the correlation, with the diversity in rise and decline rates driven by the diffusion time-scale. Circumstellar interaction models can exhibit a similar rise–decline relation, but only for a narrow range of densities, which may be problematic for these models. We find that SLSNe are approximately 3.5 mag brighter and have light curves three times broader than SNe Ibc, but that the intrinsic shapes are similar. There are a number of SLSNe with particularly broad light curves, possibly indicating two progenitor channels, but statistical tests do not cleanly separate two populations. The general spectral evolution is also presented. Velocities measured from Fe ii are similar for SLSNe and SNe Ibc, suggesting that diffusion time differences are dominated by mass or opacity. Flat velocity evolution in most SLSNe suggests a dense shell of ejecta. If opacities in SLSNe are similar to other SNe Ibc, the average ejected mass is higher by a factor 2–3. Assuming ? = 0.1?cm2?g?1, we estimate a mean (median) SLSN ejecta mass of 10 M? (6 M?), with a range of 3–30 M?. Doubling the assumed opacity brings the masses closer to normal SNe Ibc, but with a high-mass tail. The most probable mechanism for generating SLSNe seems to be the core collapse of a very massive hydrogen-poor star, forming a millisecond magnetar.

Early-time light curves of Type Ib/c supernovae from the SDSS-II Supernova Survey

Context. Type Ib/c supernovae (SNe Ib/c) have been investigated in several single-object studies. However, there is still a paucity of works concerning larger, homogeneous samples of these hydrogen-poor transients, in particular regarding the pre-maximum phase of their light curves. Aims. In this paper we present and analyse the early-time optical light curves (LCs, ugriz) of 20 SNe Ib/c from the Sloan Digital Sky Survey (SDSS) SN survey II, aiming to study their observational and physical properties as well as to derive their progenitor parameters. Methods. High-cadence, multi-band LCs are fitted with a functional model and the best-fit parameters are compared among the SN types. Bolometric LCs (BLCs) are constructed for the entire sample. We also computed the black-body (BB) temperature (TBB) and photospheric radius (Rph) evolution for each SN via BB fits on the spectral energy distributions. In addition, the bolometric properties are compared to both hydrodynamical and analytical model expectations. Results. Complementing our sample with literature data, we find that SNe Ic and Ic-BL (broad-line) have shorter rise times than those of SNe Ib and IIb. The decline rate parameter, m15, is similar among the different sub-types. SNe Ic appear brighter and bluer than SNe Ib, but this difference vanishes if we consider host galaxy extinction corrections based on colors. Templates for SN Ib/c LCs are presented. Our SNe have typical TBB of 10000 K at peak, and Rph of 10 15 cm. Analysis of the BLCs of SNe Ib and Ic gives typical ejecta masses Mej 3.6 5.7 M , energies EK 1.5 1.7 10 51 erg, and M( 56 Ni) 0.3 M . Higher values for EK and M( 56 Ni) are estimated for SNe Ic-BL (Mej 5.4 M , EK 10.7 10 51 erg, M( 56 Ni) 1.1 M ). For the majority of SNe Ic and Ic-BL we can put strong limits ( 5.9 days plateau seems to be detected. The rising part of the BLCs is reproduced by power laws with index<2. For two events (SN 2005hm and SN 2007qx) we find signatures of a possible shock break-out cooling tail. Conclusions. Based on the limits for the plateau length and on the slow rise of the BLCs, we find that in most of our SNe Ic and Ic-BL the 56 Ni is mixed up to the outer layers, suggesting that SN Ic progenitors are de facto helium poor. The derived progenitor parameters ( 56 Ni, EK , Mej) are consistent with previous works.

CALIFA, the Calar Alto Legacy Integral Field Area survey IV. Third public data release

We present a dynamical classification system for galaxies based on the shapes of their circular velocity curves (CVCs). We derive the CVCs of 40 SAURON and 42 CALIFA galaxies across Hubble sequence via a full line-of-sight integration as provided by solutions of the axisymmetric Jeans equations. We use Principal Component Analysis (PCA) applied to the circular curve shapes to find characteristic features and use a k-means classifier to separate circular curves into classes. This objective classification method identifies four different classes, which we name Slow-Rising (SR), Flat (F), Sharp-Peaked (SP) and Round-Peaked (RP) circular curves. SR-CVCs are mostly represented by late-type spiral galaxies (Scd-Sd) with no prominent spheroids in the central parts and slowly rising velocities; F-CVCs span almost all morphological types (E,S0,Sab,Sb-Sbc) with flat velocity profiles at almost all radii; SP-CVCs are represented by early-type and early-type spiral galaxies (E,S0,Sb-Sbc) with prominent spheroids and sharp peaks in the central velocities. RP-CVCs are represented by only two morphological types (E,Sa-Sab) with prominent spheroids, but RP-CVCs have much rounder peaks in the central velocities than SP-CVCs. RP-CVCs are typical for high-mass galaxies, while SR-CVCs are found for low-mass galaxies. Intermediate-mass galaxies usually have F-CVCs and SP-CVCs. Circular curve classification presents an alternative to typical morphological classification and may be more tightly linked to galaxy evolution.This paper describes the Third Public Data Release (DR3) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. Science-grade quality data for 667 galaxies are made public, including the 200 galaxies of the Second Public Data Release (DR2). Data were obtained with the integral-field spectrograph PMAS/PPak mounted on the 3.5m telescope at the Calar Alto Observatory. Three different spectral setups are available, i) a low-resolution V500 setup covering the wavelength range 3749-7500 AA (4240-7140 AA unvignetted) with a spectral resolution of 6.0 AA (FWHM), for 646 galaxies, ii) a medium-resolution V1200 setup covering the wavelength range 3650-4840 AA (3650-4620 AA unvignetted) with a spectral resolution of 2.3 AA (FWHM), for 484 galaxies, and iii) the combination of the cubes from both setups (called COMBO), with a spectral resolution of 6.0 AA and a wavelength range between 3700-7500 AA (3700-7140 AA unvignetted), for 446 galaxies. The Main Sample, selected and observed according to the CALIFA survey strategy covers a redshift range between 0.005 and 0.03, spans the color-magnitude diagram and probes a wide range of stellar mass, ionization conditions, and morphological types. The Extension Sample covers several types of galaxies that are rare in the overall galaxy population and therefore not numerous or absent in the CALIFA Main Sample. All the cubes in the data release were processed using the latest pipeline, which includes improved versions of the calibration frames and an even further improved im- age reconstruction quality. In total, the third data release contains 1576 datacubes, including ~1.5 million independent spectra. It is available at this http URL

Imprints of galaxy evolution on H II regions memory of the past uncovered by the CALIFA survey

Context. H II regions in galaxies are the sites of star formation, so they are special places for understanding the build-up of stellar mass in the universe. The line ratios of this ionized gas are frequently used to characterize the ionization conditions. In particular, the oxygen abundances are assumed to trace the chemical enrichment of galaxies. Aims. We explore the connections between the ionization conditions and the properties of the overall underlying stellar population (ionizing or not-ionizing) in H II regions, in order to uncover the actual physical connection between them. Methods. We use the H II regions catalog from the CALIFA survey, which is the largest in existence with more than 5000 H II regions, to explore their distribution across the classical [O III] lambda 5007/H beta vs. [N II] lambda 6583/H alpha diagnostic diagram, and the way it depends on the oxygen abundance, ionization parameter, electron density, and dust attenuation. The location of H II regions within this diagram is compared with predictions from photoionization models. Finally, we explore the dependence of the location within the diagnostic diagram on the properties of the host galaxies, the galactocentric distances, and the properties of the underlying stellar population. Results. The H II regions with weaker ionization strengths and more metal-rich are located in the bottom righthand area of the diagram. In contrast, those regions with stronger ionization strengths and more metal poor are located in the upper lefthand end of the diagram. Photoionization models per se do not predict these correlations between the parameters and the line ratios. The H II regions located in earlier-type galaxies, closer to the center and formed in older and more metal-rich regions of the galaxies are located in the bottom-right area of the diagram. On the other hand, those regions located in late-type galaxies in the outer regions of the disks and formed on younger and more metal-poor regions lie in the top lefthand area of the diagram. The two explored line ratios show strong correlations with the age and metallicity of the underlying stellar population. Conclusions. These results indicate that although H II regions are short-lived events, they are affected by the total underlying stellar population. One may say that H II regions keep a memory of the stellar evolution and chemical enrichment that have left an imprint on both the ionizing stellar population and the ionized gas.

SN 2015bn: A DETAILED MULTI-WAVELENGTH VIEW OF A NEARBY SUPERLUMINOUS SUPERNOVA

We present observations of SN 2015bn (= PS15ae = CSS141223-113342+004332 = MLS150211-113342+004333), a Type I superluminous supernova (SLSN) at redshift

Pan-STARRS and PESSTO search for an optical counterpart to the LIGO gravitational-wave source GW150914

z=0.1136

Shape of the oxygen abundance profiles in CALIFA face-on spiral galaxies

. As well as being one of the closest SLSNe I yet discovered, it is intrinsically brighter (

INSIGHTS ON THE STELLAR MASS-METALLICITY RELATION FROM THE CALIFA SURVEY

M_U\approx-23.1