arXiv subjects

M. Pović

Publications and source records attributed to M. Pović.

30 records · Page 2Linked to original sources

arXiv2014

The ALHAMBRA survey: an empirical estimation of the cosmic variance for merger fraction studies based on close pairs

Our goal is to estimate empirically, for the first time, the cosmic variance that affects merger fraction studies based on close pairs. We compute the merger fraction from photometric redshift close pairs with 10h^-1 kpc <= rp <= 50h^-1 kpc and Dv <= 500 km/s, and measure it in the 48 sub-fields of the ALHAMBRA survey. We study the distribution of the measured merger fractions, that follow a log-normal function, and estimate the cosmic variance sigma_v as the intrinsic dispersion of the observed distribution. We develop a maximum likelihood estimator to measure a reliable sigma_v and avoid the dispersion due to the observational errors (including the Poisson shot noise term). The cosmic variance of the merger fraction depends mainly on (i) the number density of the populations under study, both for the principal (n_1) and the companion (n_2) galaxy in the close pair, and (ii) the probed cosmic volume V_c. We find a significant dependence on neither the search radius used to define close companions, the redshift, nor the physical selection (luminosity or stellar mass) of the samples. We provide a parametrisation of the cosmic variance with n_1, n_2, and V_c, sigma_v = 0.48 n_1^{-0.54} V_c^{-0.48} (n_2/n_1)^{-0.37}. Thanks to this prescription, future merger fraction studies based on close pairs could account properly for the cosmic variance on their results.

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arXiv2013

The ALHAMBRA survey: reliable morphological catalogue of 22,051 early- and late-type galaxies

ALHAMBRA is a photometric survey designed to trace the cosmic evolution and cosmic variance. It covers a large area of ~ 4 sq. deg in 8 fields, where 7 fields overlap with other surveys, allowing to have complementary data in other wavelengths. All observations were carried out in 20 continuous, medium band (30 nm width) optical and 3 near-infrared (JHK) bands, providing the precise measurements of photometric redshifts. In addition, morphological classification of galaxies is crucial for any kind of galaxy formation and cosmic evolution studies, providing the information about star formation histories, their environment and interactions, internal perturbations, etc. We present a morphological classification of > 40,000 galaxies in the ALHAMBRA survey. We associate to every galaxy a probability to be early-type using the automated Bayesian code galSVM. Despite of the spatial resolution of the ALHAMBRA images (~ 1 arcsec), for 22,051 galaxies we obtained the contamination by other type of less than 10%. Of those, 1,640 and 10,322 galaxies are classified as early- (down to redshifts ~ 0.5) and late-type (down to redshifts ~ 1.0), respectively, with magnitudes F613W < 22.0. In addition, for magnitude range 22.0 < F613W < 23.0 we classified other 10,089 late-type galaxies with redshifts < 1.3. We show that the classified objects populate the expected regions in the colour-mass and colour-magnitude planes. The presented dataset is especially attractive given the homogeneous multi-wavelength coverage available in the ALHAMBRA fields, and is intended to be used in a variety of scientific applications. The low-contamination catalogue (< 10%) is made publicly available with the present paper.

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arXiv2013

The ALHAMBRA survey: Discovery of a faint QSO at z = 5.41

We aim to illustrate the potentiality of the Advanced Large, Homogeneous Area, Medium-Band Redshift Astronomical (ALHAMBRA) survey to investigate the high redshift universe through the detection of quasi stellar objects (QSOs) at redshifts larger than 5. The search for z>5 QSOs candidates was done by fitting an extensive library of spectral energy distributions --including active and non-active galaxy templates as well as stars-- to the photometric database of the ALHAMBRA survey (composed of 20 optical medium-band plus the 3 broad-band JHKs filters). Our selection over ~1 square degree of ALHAMBRA data (~1/4 of the total area covered by the survey), combined with GTC/OSIRIS spectroscopy, has yielded the identification of an optically faint QSO at very high redshift (z = 5.41). The QSO has an absolute magnitude of ~-24 at the 1450Å continuum, a bolometric luminosity of ~2x10^46 erg/s and an estimated black hole mass of ~10^8 Msolar. This QSO adds itself to a reduced number of known UV faint sources at these redshifts. The preliminary derived space density is compatible with the most recent determinations of the high-z QSO luminosity functions (QLF). This new detection shows how ALHAMBRA, as well as forthcoming well designed photometric surveys, can provide a wealth of information on the origin and early evolution of this kind of objects.

astro-ph.CO↗

arXiv2013

Lyman break and UV-selected galaxies at z ~ 1: II. PACS-100um/160um FIR detections

We report the PACS-100um/160um detections of a sample of 42 GALEX-selected and FIR-detected Lyman break galaxies (LBGs) at z ~ 1 located in the COSMOS field and analyze their ultra-violet (UV) to far-infrared (FIR) properties. The detection of these LBGs in the FIR indicates that they have a dust content high enough so that its emission can be directly detected. According to a spectral energy distribution (SED) fitting with stellar population templates to their UV-to-near-IR observed photometry, PACS-detected LBGs tend to be bigger, more massive, dustier, redder in the UV continuum, and UV-brighter than PACS-undetected LBGs. PACS-detected LBGs at z ~ 1 are mostly disk-like galaxies and are located over the green-valley and red sequence of the color-magnitude diagram of galaxies at their redshift. By using their UV and IR emission, we find that PACS-detected LBGs tend to be less dusty and have slightly higher total star-formation rates (SFRs) than other PACS-detected UV-selected galaxies within their same redshift range. As a consequence of the selection effect due to the depth of the FIR observations employed, all our PACS-detected LBGs are LIRGs. However, none of them are in the ULIRG regime, where the FIR observations are complete. The finding of ULIRGs-LBGs at higher redshifts suggests an evolution of the FIR emission of LBGs with cosmic time. In an IRX-$β$ diagram, PACS-detected LBGs at z ~ 1 tend to be located around the relation for local starburst similarly to other UV-selected PACS-detected galaxies at their same redshift. Consequently, the dust-correction factors obtained with their UV continuum slope allow to determine their total SFR, unlike at higher redshifts. However, the dust attenuation derived from UV to NIR SED fitting overestimates the total SFR for most of our PACS-detected LBGs in age-dependent way: the overestimation factor is higher in younger galaxies.

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arXiv2013

X-ray luminosity functions of different morphological and X-ray type AGN populations

Luminosity functions are one of the most important observational clues when studying galaxy evolution over cosmic time. In this paper we present the X-ray luminosity functions of X-ray detected AGN in the SXDS and GWS fields. The limiting fluxes of our samples are 9.0x10^(-15) and 4.8x10^(-16) erg/cm^2/sec^(-1) in the 0.5 - 7.0 keV band in the two fields, respectively. We carried out analysis in three X-ray bands and in two redshift intervals up to z < 1.4. Moreover, we derive the luminosity functions for different optical morphologies and X-ray types. We confirm strong luminosity evolution in all three bands, finding the most luminous objects at higher redshift. However, no signs of density evolution are found in any tested X-ray band. We obtain similar results for compact and early-type objects. Finally, we observe the `Steffen effect', where X-ray type-1 sources are more numerous at higher luminosities in comparison with type-2 sources.

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arXiv2012

AGN-Host Galaxy Connection: Morphology and Colours of X-ray Selected AGN at z < 2

The connection between AGN and their host galaxies has been widely studied over recent years, showing it to be of great importance for providing answers to some fundamental questions related with AGN fueling mechanisms, their formation and evolution. Using X-ray and one of the deepest broad-band optical data sets, we studied morphology and colours in relationship with X-ray properties for sources at redshifts z < 2.0, using a sample of 262 AGN in the Subaru/XMM-Newton Deep Survey (SXDS). Morphological classification was obtained using the galSVM code, one of the new methods useful especially when dealing with high-redshift sources and low-resolution data. Colour-magnitude diagrams were studied in relationship with redshift, morphology, X-ray obscuration, and X-ray-to-optical flux ratio. Finally, the significance of different regions was analysed on colour-magnitude diagrams, relating the observed properties of AGN populations with some models of their formation and evolution.

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arXiv2010

OTELO survey: optimal emission-line flux determination with OSIRIS/GTC

Emission-line galaxies are important targets for understanding the chemical evolution of galaxies in the universe. Deep, narrow-band imaging surveys allow to detect and study the flux and the equivalent widths (EW) of the emission line studied. The present work has been developed within the context of the OTELO project, an emission line survey using the Tunable Filters (TF) of OSIRIS, the first generation instrument on the GTC 10.4m telescope located in La Palma, Spain, that will observe through selected atmospheric windows relatively free of sky emission lines. With a total survey area of 0.1 square degrees distributed in different fields, reaching a 5 σdepth of 10^-18 erg/cm^2/s and detecting objects of EW < 0.3 A, OTELO will be the deepest emission line survey to date. As part of the OTELO preparatory activities, the objective of this study is to determine the best combination of sampling and full width at half maximum (FWHM) for the OSIRIS tunable filters for deblending Hαfrom [NII] lines by analyzing the flux errors obtained. We simulated the OTELO data by convolving a complete set of synthetic HII galaxies in EW with different widths of the OSIRIS TFs. We estimated relative flux errors of the recovered Hαand [NII]6583 lines. We found that, for the red TF, a FWHM of 12 A and a sampling of 5 A is an optimal combination that allow deblending Hαfrom the [NII]6583 line with a flux error lower than 20%. This combination will allow estimating SFRs and metallicities using the Hαflux and the N2 method, respectively.

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arXiv2010

Evolution of the Fundamental Plane of 0.2<z<1.2 Early-type galaxies in the EGS

The Fundamental Plane relates the structural properties of early-type galaxies such as its surface brightness and effective radius with its dynamics. The study of its evolution has therefore important implications for models of galaxy formation and evolution. This work aims to identify signs of evolution of early-type galaxies through the study of parameter correlations using a sample of 135 field galaxies extracted from the Extended Groth Strip in the redshift range 0.2 =0.7. However, the scatter in the FP is reduced by half when we allow the FP slope to evolve, suggesting a different evolution of early-type galaxies according to their intrinsic properties. The study of the Kormendy relation shows the existence of a population of very compact (Re<2 Kpc) and bright galaxies (-21.5>Mg>-22.5), of which there are only a small fraction (0.4%) at z=0. The evolution of these compact objects is mainly caused by an increase in size that could be explained by the action of dry minor mergers, and this population is responsible for the evolution detected in the Fundamental Plane.

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arXiv2010

Evolution of the infrared Tully-Fisher relation up to z=1.4

The Tully-Fisher relation (TFR) represents a connection between fundamental galaxy parameters, such as its total mass and the mass locked in stars. Therefore, the study of the evolution of this relation in the optical and infrared bands can provide valuable information about the evolution of the individual galaxies through the changes found in each band. This work aims to study the TFR at high redshift in the B, V, R, I, and K-bands by comparison with the local relations derived from a large sample of galaxies in the redshift range 0.1<z<0.3, processed in the same way, and with the same instrumental constraints that the high-redshift sample. Using the large photometric information available in the AEGIS database, we have studied the best procedure to obtain reliable k-corrections. Instrumental magnitudes are then k and extinction corrected and the absolute magnitudes derived, using the concordance cosmological model. The rotational velocities have been obtained from the widths of optical lines using DEEP2 spectra. Finally, morphology has been determined via visual classification of the HST images. We detect evolution in the B, V and R-band TFRs in the sense that galaxies were brighter in the past for the same rotation velocity. The change in luminosity is more noticeable in the bluer bands. This colour evolution, unnoticed in our previous work (Fernández Lorenzo et al. 2009) has been detected thanks to the more reliable k-corrections carried out in this paper, which included photometry from B to IRAC bands. The change in the (V-K) and (R-I) colours (for a fixed velocity) could be interpreted as an ageing of the stellar populations as consequence of the star formation decrease since z=1.25. In addition, we conclude that spiral galaxies could have doubled their stellar masses in the last 8.6 Gyr.

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arXiv2009

On the Anticorrelation Between Galaxy Light Concentration and X-ray-to-Optical Flux Ratio

Active Galactic Nuclei (AGN) play an important role in many aspects of the modern cosmology, and of particular interest is the issue of the interplay between AGN and their host galaxy. Using X-ray and optical data sets, we have explored the properties of a large sample of AGNs in the Subaru/XMM-Newton Deep Survey (SXDS) field, and studied their evolution in relation with the evolution of their host galaxy. We present here an anticorrelation between X-ray-to-optical flux ratio (X/O) and galaxy light concentration (C), which has been found for the first time and might suggest that early type galaxies, having poor matter supply to feed the AGN activity, have lower Eddington rates than those of late type galaxies.

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arXiv2009

OTELO Survey: Deep BVRI broadband photometry of the Groth strip. II Properties of X-ray Emitters

The Groth field is one of the sky regions that will be targeted by the OTELO (OSIRIS Tunable Filter Emission Line Object) survey in the optical 820 nm and 920 nm atmospheric windows. This field has been observed by AEGIS (All-wavelength Extended Groth strip International Survey) covering the full spectral range, from X-rays to radio waves. Chandra X-ray data with total exposure time of 200ksec are analyzed and combined with optical broadband data of the Groth field in order to study a set of structural parameters of the X-ray emitters and its relation with X-ray properties. We processed the raw, public X-ray data using the Chandra Interactive Analysis of Observations and determined and analyzed different structural parameters in order to produce a morphological classification of X-ray sources. Finally, we analyzed the angular clustering of these sources using 2-point correlation functions. We present a catalog of 340 X-ray emitters with optical counterpart. We obtained the number counts and compared them with AEGIS data. Objects have been classified by nuclear type using a diagnostic diagram relating X-ray-to-optical ratio (X/O) to hardness ratio (HR). Also, we combined structural parameters with other X-ray and optical properties, and found for the first time an anticorrelation between the X/O ratio and the Abraham concentration index which might suggest that early type galaxies have lower Eddington rates than those of late type galaxies. A significant positive angular clustering was obtained from a preliminary analysis of 4 subsamples of the X-ray sources catalog. The clustering signal of the opticaly extended counterparts is similar to that of strongly clustered populations like red and very red galaxies, suggesting that the environment plays an important role in AGN phenomena.

astro-ph.CO↗

arXiv2009

Evolution of the optical Tully-Fisher relation up to z=1.3

The study of the evolution of the Tully-Fisher relation has been controversial in the past years. The main difficulty is in determining the required parameters for intermediate and high redshift galaxies. This work aims to identify the main problems of the study of the Tully-Fisher relation at high redshift using optical emission lines, in order to draw conclusions about the possible evolution of this relation in the B, R, and I-bands. With this aim, the rotational velocities obtained from the widths of different optical lines using DEEP2 spectra are compared. Morphology has been determined via HST images, using and comparing different methodologies. Instrumental magnitudes are then corrected for K and extinction and the absolute magnitudes derived for the concordance cosmological model. Finally, the optical Tully-Fisher relations in B, R, and I-bands at different redshifts up to z = 1.3 are derived. Although most studies (this one included) find evidence of evolution, the results are not conclusive enough, since the possible luminosity evolution is within the scattering of the relation, and the evolution in slope is difficult to determine because at high redshift only the brightest galaxies can be measured. Nevertheless, our study shows a clear tendency, which is the same for all bands studied, that favours a luminosity evolution where galaxies were brighter in the past for the same rotation velocity. This result also implies that the colour of the Tully-Fisher relation does not change with redshift, supporting the collapse model versus the accretion model of disc galaxy formation.

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