Self-consistent modeling of stars and dust emission of IR-bright galaxies at intermediate redshift

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Astrofísica y Ciencias de la Atmósfera, leída el 17-12-2015Las distribuciones espectrales de energía (SEDs) de galaxias con polvo y formación estelar a desplazamientos al rojo intermedio son caracterizadas usualmente con modelos que asumen un ́unico brote para representar las historia de formación estelar (SFH) de las distintas poblaciones que constituyen estos objetos. Adeḿas, la relación entre la atenuación de la emisión estelar en el espectro visible debida al polvo y su posterior re-emisi ́on en el infrarrojo lejano (FIR) ha sido desestimada cuando se determinan las propiedades físicas de estas galaxias, como la masa y la tasa de formación estelar (SFR). En esta tesis investigamos las propiedades estelares de una muestra de 19 galaxias seleccionadas en el FIR en el intervalo de desplazamiento al rojo 0.6 ≤ z ≤ 1.5, analizando su SEDs desde el UV hasta el FIR. La muestra se deriva de objetos con 3 o ḿas medidas fotométricas en el FIR, una tomada a 70 μm con MIPS en Spitzer y ḿınimo otras dos adquiridas con PACS y/o SPIRE en Herschel en la región del Subaru/XMMNewton Deep Survey. Esta fotometría permite estimar de forma precisa la luminosidad total en el IR (LTIR, integrada entre 8 y 1000 μm) de estas galaxias brillantes en el IR (LIRGs and ULIRGs). Las SEDs desde el UV hasta el FIR son ajustadas usando modelos de poblaciones estelares y emisión del polvo provenientes de programas (Synthesizer y CIGALE) que conectan usando técnicas de balance energético la atenuación de la emisión estelar debida al polvo y su posterior re-emisión en el FIR. Asumimos una SFH de referencia descrita por una población estelar joven traslapando una población estelar evolucionada, ambas caracterizadas con funciones exponenciales decrecientes. Determinamos el impacto en nuestros resultados cuando se constri ˜ne o no, la atenuación de la emisión estelar usando el método de balance energético, y su efecto en combinación con modelos que asumen una población estelar en lugar de dos. Este análisis con balance energético permite: 1) caracterizar las poblaciones estelares de (U)LIRGs con propiedades físicas robustas determinadas al romper la degeneración edad-polvo; 2) estimar adecuadamente la cantidad de atenuación de la emisión estelar en estas galaxias; 3) mejorar las estimaciones de masa estelar y SFR en (U)LIRGs; 4) calcular el tiempo que transcurren las galaxias en la fase (U)LIRG, y la masa estelar ix x que se agrega a las galaxias en dicha fase; 5) determinar que propiedades de las poblaciones estelares ejercen mayor impacto en la estimación de masas estelares y SFRs en (U)LIRGs; y 6) evaluar como las suposiciones a priori y el uso de programas diferentes en el modelado afectan los resultados en propiedades estelares de (U)LIRGs.The Spectral Energy Distributions (SEDs) of dusty star-forming galaxies at intermediate redshifts are usually characterized with models that naively assume only one burst (short or extended in time) as representative star formation history (SFH) of the stellar populations of these galaxies, which are obviously much more complex. Moreover, the relation between the optical light attenuation and posterior re-emission at far-infrared (FIR) wavelengths due to dust has been traditionally unappreciated when deriving the physical properties of these objects, such as the stellar mass and star formation rate (SFR). In this thesis we investigate the stellar properties of a FIR selected sample of 19 star-forming galaxies in the redshift range 0.6 ≤ z ≤ 1.5 by analyzing their UV-to- FIR SEDs. The sample is based in three or more FIR detections, one from Spitzer- MIPS 70 μm and at least two from PACS and/or SPIRE on Herschel observed in the Subaru/XMM-Newton Deep Survey field. These FIR data allow us to accurately determine the total infrared luminosity (LTIR, integrated from 8 to 1000 μm) of such (ultra)- luminous infrared galaxies (LIRGs and ULIRGs). The full UV-to-FIR SEDs are fitted to stellar population and dust emission models using codes (Synthesizer and CIGALE) which manage the attenuation of stellar light and dust re-emission with energy balance techniques. We assume a fiducial SFH depicted by a young stellar population on top of an evolved population, each parameterized with a decaying exponential function. We compare the impact on our results of including and excluding the FIR data to constrain the amount of attenuation of stellar light, as well of using this constrain assuming one single stellar population instead of two. Our auto-consistent analysis of the stellar light obscuration and dust emission provides: 1) reliable physical properties of the stellar populations of (U)LIRGs by breaking the age-dust degeneracy; 2) accurate values of the amount of attenuation of stellar light in these galaxies; 3) improved stellar mass and SFR estimations of IR-bright galaxies; 4) estimates of the time spent by galaxies in the (U)LIRG phase, and of the corresponding amount of stellar mass added in this phase; 5) the stellar properties having more impact in the determination of stellar masses and SFRs of IR-bright galaxies; and 6) an evaluation of how a priori assumptions and usage v vi of different codes in the modeling affect the results for the stellar population properties of (U)LIRGs.Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEunpu

Differential attenuation in star-forming galaxies at 0.3 less than or similar to z less than or similar to 1.5 in the SHARDS/CANDELS fields

We use a sample of 706 galaxies, selected as [O II]lambda 3727 ([O II]) emitters in the Survey for High-z Absorption Red and Dead Sources SHARDS) on the CANDELS/GOODS-N field, to study the differential attenuation of the nebular emission with respect to the stellar continuum. The sample includes only galaxies with a counterpart in the infrared and log(10) (M-*/M-circle dot) > 9, over the redshift interval 0.3 less than or similar to z less than or similar to 1.5. Our methodology consists in the comparison of the star formation rates inferred from [O II] and Haemission lines with a robust quantification of the total star-forming activity (SFR TOT) that is independently estimated based on both infrared and ultraviolet (UV) luminosities. We obtain f = E(B - V)(stellar)/E(B - V)(nebular) = 0.69(0.69)(0.71) and 0.55(0.53)(0.56) for [O II] and H alpha, respectively. Our resulting f-factors display a significant positive correlation with the UV attenuation and shallower or not-significant trends with the stellar mass, the SFR TOT, the distance to the main sequence, and the redshift. Finally, our results favour an average nebular attenuation curve similar in shape to the typical dust curve of local starbursts

SHARDS: constraints on the dust attenuation law of star-forming galaxies at z∼2

We make use of the Survey of High-z Absorption Red and Dead Sources, an ultradeep (<26.5AB) galaxy survey that provides optical photospectra at resolution R similar to 50, via medium-band filters (FWHM similar to 150 angstrom). This data set is combined with ancillary optical and NIR fluxes to constrain the dust attenuation law in the rest-frame NUV region of star-forming galaxies within the redshift window 1.5 < z < 3. We focus on the NUV bump strength (B) and the total-to-selective extinction ratio (R-V), targeting a sample of 1753 galaxies. By comparing the data with a set of population synthesis models coupled to a parametric dust attenuation law, we constrain R-V and B, as well as the colour excess, E(B - V). We find a correlation between R-V and B, which can be interpreted either as a result of the grain size distribution, or a variation of the dust geometry among galaxies. According to the former, small dust grains are associated with a stronger NUV bump. The latter would lead to a range of clumpiness in the distribution of dust within the interstellar medium of star-forming galaxies. The observed wide range of NUV bump strengths can lead to a systematic in the interpretation of the UV slope beta typically used to characterize the dust content. In this study, we quantify these variations, concluding that the effects are Delta beta similar to 0.4

SHARDS: Constraints on the dust attenuation law of star-forming galaxies at z~2

We make use of SHARDS, an ultra-deep (<26.5AB) galaxy survey that provides optical photo-spectra at resolution R~50, via medium band filters (FWHM~150A). This dataset is combined with ancillary optical and NIR fluxes to constrain the dust attenuation law in the rest-frame NUV region of star-forming galaxies within the redshift window 1.5<z<3. We focus on the NUV bump strength (B) and the total-to-selective extinction ratio (Rv), targeting a sample of 1,753 galaxies. By comparing the data with a set of population synthesis models coupled to a parametric dust attenuation law, we constrain Rv and B, as well as the colour excess, E(B-V). We find a correlation between Rv and B, that can be interpreted either as a result of the grain size distribution, or a variation of the dust geometry among galaxies. According to the former, small dust grains are associated with a stronger NUV bump. The latter would lead to a range of clumpiness in the distribution of dust within the interstellar medium of star-forming galaxies. The observed wide range of NUV bump strengths can lead to a systematic in the interpretation of the UV slope ($\beta$) typically used to characterize the dust content. In this study we quantify these variations, concluding that the effects are $\Delta\beta$~0.4.Comment: 13 pages, 11+2 figures, 3 tables. MNRAS, in pres

Ultraviolet to far infrared self-consistent analysis of the stellar populations of massive starburst galaxies at intermediate redshifts

We study in detail the properties of the stellar populations of 111 massive [log (M-*/M-circle dot) >= 10] dusty [far-infrared (FIR)-selected] starburst (SFR/SFRMS > 2) galaxies at 0.7 < z < 1.2. For that purpose, we use self-consistent methods that analyse the UV-to-FIR broad-band observations in terms of the stellar light and dust re-emission with energy-balance techniques. We find that the emission of our starburst galaxies can be interpreted as a recent star formation episode superimposed on a more evolved stellar population. On average, the burst age is similar to 80 Myr and its attenuation similar to 2.4 mag. Assuming our starburst galaxies at half their lifetimes, we infer a duration of the starburst phase of similar to 160 Myr. The median stellar mass and star formation rate (SFR) are log (M-*/M-circle dot) similar to 10.6 and similar to 220 M(circle dot)yr(-1). Assuming this SFR and the inferred duration of the starburst phase, the stellar mass added during this phase corresponds to similar to 40 per cent the median stellar mass of our sample. The young-population age determines the position of our galaxies in the M-*-SFR plane. Galaxies located at the largest distances of the MS present shorter young-population ages. The properties of the underlying stellar population cannot be constrained accurately with our broad-band data. We also discuss the impact of including the FIR data and energy-balance techniques in the analysis of the properties of the stellar populations in starburst galaxies

The CANDELS/SHARDS multiwavelength catalog in GOODS-N: photometry, photometric redshifts, stellar masses, emission-line fluxes, and star formation rates

We present a WFC3 F160W (H-band) selected catalog in the CANDELS/GOODS-N field containing photometry from the ultraviolet (UV) to the far-infrared (IR), photometric redshifts, and stellar parameters derived from the analysis of the multiwavelength data. The catalog contains 35,445 sources over the 171 arcmin^(2) of the CANDELS F160W mosaic. The 5σ detection limits (within an aperture of radius 0”. 17) of the mosaic range between H = 27.8, 28.2, and 28.7 in the wide, intermediate, and deep regions, which span approximately 50%, 15%, and 35% of the total area. The multiwavelength photometry includes broadband data from the UV (U band from KPNO and LBC), optical (HST/ACS F435W, F606W, F775W, F814W, and F850LP), near-to-mid IR (HST/WFC3 F105W, F125W, F140W, and F160W; Subaru/MOIRCS Ks; CFHT/Megacam K; and Spitzer/IRAC 3.6, 4.5, 5.8, and 8.0 μm), and far-IR (Spitzer/MIPS 24 μm, HERSCHEL/PACS 100 and 160 μm, SPIRE 250, 350 and 500 μm) observations. In addition, the catalog also includes optical medium-band data (R ∼ 50) in 25 consecutive bands, λ = 500–950 nm, from the SHARDS survey and WFC3 IR spectroscopic observations with the G102 and G141 grisms (R ∼ 210 and 130). The use of higher spectral resolution data to estimate photometric redshifts provides very high, and nearly uniform, precision from z = 0–2.5. The comparison to 1485 good-quality spectroscopic redshifts up to z ∼ 3 yields Δz/(1 + z_(spec)) = 0.0032 and an outlier fraction of η = 4.3%. In addition to the multiband photometry, we release value-added catalogs with emission-line fluxes, stellar masses, dust attenuations, UV- and IR-based star formation rates, and rest-frame colors

Probing the Star Formation Main Sequence down to 10810^{8} M⊙_\odot at 1.0<z<3.01.0<z<3.0

We investigate the star formation main sequence (MS) (SFR-M$_{\star}$) down to 10$^{8-9}\mathrm{M}_\odot$ using a sample of 34,061 newly-discovered ultra-faint ($27\lesssim i \lesssim 30$ mag) galaxies at $1<z<3$ detected in the GOODS-N field. Virtually these galaxies are not contained in previous public catalogs, effectively doubling the number of known sources in the field. The sample was constructed by stacking the optical broad-band observations taken by the HST/GOODS-CANDELS surveys as well as the 25 ultra-deep medium-band images gathered by the GTC/SHARDS project. Our sources are faint (average observed magnitudes $\sim28.2$ mag, $\sim27.9$ mag), blue (UV-slope $\sim-1.9$), star-forming (rest-frame colors $\sim0.10$ mag, $\sim0.17$ mag) galaxies. These observational characteristics are identified with young (mass-weighted age $\sim0.014$ Gyr) stellar populations subject to low attenuations ($\sim0.30$ mag). Our sample allows us to probe the MS down to $10^{8.0}\,\mathrm{M}_\odot$ at $z=1$ and $10^{8.5}\,\mathrm{M}_\odot$ at $z=3$, around 0.6 dex deeper than previous analysis. In the low-mass galaxy regime, we find an average value for the slope of 0.97 at $1<z<2$ and 1.12 at $2<z<3$. Nearly $\sim$60% of our sample presents stellar masses in the range $10^{6-8}$ M$_\odot$ between $1<z<3$. If the slope of the MS remained constant in this regime, the sources populating the low-mass tail of our sample would qualify as starburst galaxies.Comment: 34 pages, 16 figures, 9 tables. Accepted for publication to Ap

SHARDS: A global view of the star formation activity at z~0.84 and z~1.23

In this paper, we present a comprehensive analysis of star-forming galaxies (SFGs) at intermediate redshifts (z~1). We combine the ultra-deep optical spectro-photometric data from the Survey for High-z Absorption Red and Dead Sources (SHARDS) with deep UV-to-FIR observations in the GOODS-N field. Exploiting two of the 25 SHARDS medium-band filters, F687W17 and F823W17, we select [OII] emission line galaxies at z~0.84 and z~1.23 and characterize their physical properties. Their rest-frame equivalent widths (EW$_{\mathrm{rf}}$([OII])), line fluxes, luminosities, star formation rates (SFRs) and dust attenuation properties are investigated. The evolution of the EW$_{\mathrm{rf}}$([OII]) closely follows the SFR density evolution of the universe, with a trend of EW$_{\mathrm{rf}}$([OII])$\propto$(1+z)$^3$ up to redshift z~1, followed by a possible flattening. The SF properties of the galaxies selected on the basis of their [OII] emission are compared with complementary samples of SFGs selected by their MIR and FIR emission, and also with a general mass-selected sample of galaxies at the same redshifts. We demonstrate observationally that the UVJ diagram (or, similarly, a cut in the specific SFR) is only partially able to distinguish the quiescent galaxies from the SFGs. The SFR-M$_*$ relation is investigated for the different samples, yelding a logarithmic slope ~1, in good agreement with previous results. The dust attenuations derived from different SFR indicators (UV(1600), UV(2800), [OII], IR) are compared and show clear trends with respect to both the stellar mass and total SFR, with more massive and highly star-forming galaxies being affected by stronger dust attenuation.Comment: Replaced to match the accepted version (24 pages, 1 table, 17 figures). Published in ApJ, 812, 155 (2015): http://stacks.iop.org/0004-637X/812/15

The impact of Early Dark Energy on non-linear structure formation

We study non-linear structure formation in high-resolution simulations of Early Dark Energy (EDE) cosmologies and compare their evolution with the standard LCDM model. Extensions of the spherical top-hat collapse model predict that the virial overdensity and linear threshold density for collapse should be modified in EDE model, yielding significant modifications in the expected halo mass function. Here we present numerical simulations that directly test these expectations. Interestingly, we find that the Sheth & Tormen formalism for estimating the abundance of dark matter halos continues to work very well in its standard form for the Early Dark Energy cosmologies, contrary to analytic predictions. The residuals are even slightly smaller than for LCDM. We also study the virial relationship between mass and dark matter velocity dispersion in different dark energy cosmologies, finding excellent agreement with the normalization for Lambda as calibrated by Evrard et al.(2008). The earlier growth of structure in EDE models relative to LCDM produces large differences in the mass functions at high redshift. This could be measured directly by counting groups as a function of the line-of-sight velocity dispersion, skirting the ambiguous problem of assigning a mass to the halo. Using dark matter substructures as a proxy for member galaxies, we demonstrate that even with 3-5 members sufficiently accurate measurements of the halo velocity dispersion function are possible. Finally, we determine the concentration-mass relationship for our EDE cosmologies. Consistent with the earlier formation time, the EDE halos show higher concentrations at a given halo mass. We find that the magnitude of the difference in concentration is well described by the prescription of Eke et al.(2001) for estimating halo concentrations.Comment: 17 pages,17 figure

Variation in Fish Abundance, Diversity and Assemblage Structure in Seagrass Meadows across the Atlanto-Mediterranean Province

Seagrasses worldwide provide key habitats for fish assemblages. Biogeographical disparities in ocean climate conditions and seasonal regimes are well-known drivers of the spatial and temporal variation in seagrass structure, with potential effects on associated fish assemblages. Whether taxonomically disparate fish assemblages support a similar range of ecological functions remains poorly tested in seagrass ecosystems. In this study, we examined variation in the abundance, diversity (from a taxonomic and functional perspective), and assemblage structure of fish community inhabiting nine meadows of the seagrass Cymodocea nodosa across three regions in the Mediterranean (Mallorca and Alicante) and the adjacent Atlantic (Gran Canaria), and identified which attributes typifying the structure of meadows, and large-scale variability in ocean climate, contributed most to explaining such ecological variation. Despite a similar total number of species between Mallorca and Gran Canaria, the latter region had more taxonomically and functionally diverse fish assemblages relative to the western Mediterranean regions, which translated into differences in multivariate assemblage structure. While variation in the abundance of the most conspicuous fish species was largely explained by variation in seagrass structural descriptors, most variation in diversity was accounted for by a descriptor of ocean climate (mean seasonal SST), operating at regional scales. Variation in fish assemblage structure was, to a lesser extent, also explained by local variability in seagrass structure. Beyond climatic drivers, our results suggest that lower temporal variability in the canopy structure of C. nodosa meadows in Gran Canaria provides a more consistent source of food and protection for associated fish assemblages, which likely enhances the more abundant and diverse fish assemblages thereEn prens