Vicent J. Martinez

Context. The observed Lyman-alpha (Lyα) line profile is a convolution of the complex Lyα radiative transfer taking place in the interstellar, circumgalactic, and intergalactic media (ISM, CGM, and IGM, respectively). Discerning the different components of the Lyα line is crucial in order to use it as a probe of galaxy formation or the evolution of the IGM. Aims. We aim to present the second version of zELDA (redshift Estimator for Line profiles of Distant Lyman-Alpha emitters), an open-source Python module focused on modelling and fitting observed Lyα line profiles. This new version of zELDA focuses on disentangling the galactic from the IGM effects. Methods. We built realistic Lyα line profiles that include the ISM and IGM contributions by combining the Monte Carlo radiative-transfer simulations for the so-called shell model (ISM) and IGM transmission curves generated from TNG100. We used these mock line profiles to train different artificial neural networks. These use the observed spectrum as input and the outflow parameters of the best fitting ‘shell model’ as output along with the redshift and Lyα emission IGM escape fraction of the source. Results. We measured the accuracy of zELDA on mock Lyα line profiles. We find that zELDA is capable of reconstructing the ISM emerging Lyα line profile with high levels of accuracy (Kolmogórov-SmirnovConclusions. This work represents a step forward in the high-precision reconstruction of IGM-attenuated Lyα line profiles. zELDA allows the disentanglement of the galactic and IGM contribution shaping the Lyα line shape and thus allows us to use Lyα as a tool to study galaxy and ISM evolution.

Dark matter simulations require statistical techniques to properly identify and classify their halos and structures. Nonparametric solutions provide catalogs of these structures but lack the additional learning of a model-based algorithm and might misclassify particles in merging situations. With mixture models, we can simultaneously fit multiple density profiles to the halos that are found in a dark matter simulation. In this work, we use the Einasto profile to model the halos found in a sample of the Bolshoi simulation, and we obtain their location, size, shape, and mass. Our code is implemented in the R statistical software environment and can be accessed on https://github.com/LluisHGil/darkmix.

One of the basic tenets of exobiology is the need for a liquid substratum in which life can arise, evolve, and develop. The most common version of this idea involves the necessity of water to act as such a substratum, both because that is the case on Earth and because it seems to be the most viable liquid for chemical reactions that lead to life. Other liquid media that could harbor life, however, have occasionally been put forth. In this work, we investigate the relative probability of finding superficial seas on rocky worlds that could be composed of nine different, potentially abundant, liquids, including water. We study the phase space size of habitable zones defined for those substances. The regions where there can be liquid around every type of star are calculated by using a simple model, excluding areas within a tidal locking distance. We combine the size of these regions with the stellar abundances in the Milky Way disk and modulate our result with the expected radial abundance of planets via a generalized Titius-Bode law, as statistics of exoplanet orbits seem to point to its adequateness. We conclude that seas of ethane may be up to nine times more frequent among exoplanets than seas of water, and that solvents other than water may play a significant role in the search for extrasolar seas.

Context.Knowing the exact shape of the ultraviolet (UV) luminosity function (LF) of high-redshift galaxies is important to understand the star formation history of the early Universe. However, the uncertainties, especially at the faint and bright ends of the LFs, remain significant.Aims.In this paper, we study the UV LF of redshiftz =2.5 – 4.5 galaxies in 2.38 deg²of ALHAMBRA data withI≤ 24. Thanks to the large area covered by ALHAMBRA, we particularly constrain the bright end of the LF. We also calculate the cosmic variance and the corresponding bias values for our sample and derive their host dark matter halo masses.Methods.We have used a novel methodology based on redshift and magnitude probability distribution functions (PDFs). This methodology robustly takes into account the uncertainties due to redshift and magnitude errors, shot noise, and cosmic variance, and models the LF in two dimensions (z,M_UV).Results.We find an excess of bright *M^*_UVgalaxies as compared to the studies based on broad-band photometric data. However, our results agree well with the LF of the magnitude-selected spectroscopic VVDS data. We measure high bias values,b ~8 – 10, that are compatible with the previous measurements considering the redshifts and magnitudes of our galaxies and further reinforce the real high-redshift nature of our bright galaxies.Conclusions.We call into question the shape of the LF at its bright end; is it a double power-law as suggested by the recent broad-band photometric studies or rather a brighter Schechter function, as suggested by our multi-filter analysis and the spectroscopic VVDS data.

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Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics

Aims. Our goal is to study the evolution of the B-band luminosity function (LF) since z ~ 1 using ALHAMBRA data.Methods. We used the photometric redshift and the I-band selection magnitude probability distribution functions (PDFs) of those ALHAMBRA galaxies with I ≤ 24 mag to compute the posterior LF. We statistically studied quiescent and star-forming galaxies using the template information encoded in the PDFs. The LF covariance matrix in redshift – magnitude – galaxy type space was computed, including the cosmic variance. That was estimated from the intrinsic dispersion of the LF measurements in the 48 ALHAMBRA sub-fields. The uncertainty due to the photometric redshift prior is also included in our analysis.Results. We modelled the LF with a redshift-dependent Schechter function affected by the same selection effects than the data. The measured ALHAMBRA LF at 0.2 ≤ z < 1 and the evolving Schechter parameters both for quiescent and star-forming galaxies agree with previous results in the literature. The estimated redshift evolution of MB * ∝ Qz is Q SF = −1.03 ± 0.08 and Q Q = −0.80 ± 0.08, and of log 10 φ ∗ ∝ Pz is P SF = −0.01 ± 0.03 and P Q = −0.41 ± 0.05. The measured faint-end slopes are α SF = −1.29 ± 0.02 and α Q = −0.53 ± 0.04. We find a significant population of faint quiescent galaxies with M B ≳ −18, modelled by a second Schechter function with slope β = −1.31 ± 0.11.Conclusions. We present a robust methodology to compute LFs using multi-filter photometric data. The application to ALHAMBRA shows a factor 2.55 ± 0.14 decrease in the luminosity density j B of star-forming galaxies, and a factor 1.25 ± 0.16 increase in the j B of quiescent ones since z = 1, confirming the continuous build-up of the quiescent population with cosmic time. The contribution of the faint quiescent population to j B increases from 3% at z = 1 to 6% at z = 0. The developed methodology will be applied to future multi-filter surveys such as J-PAS.

The original ALHAMBRA catalogue contained over 400 000 galaxies selected using a synthetic F814W image, to the magnitude limit AB(F814W) ≈ 24.5. Given the photometric redshift depth of the ALHAMBRA multiband data (〈z〉 = 0.86) and the approximately I-band selection, there is a noticeable bias against red objects at moderate redshift. We avoid this bias by creating a new catalogue selected in the K_s band. This newly obtained catalogue is certainly shallower in terms of apparent magnitude, but deeper in terms of redshift, with a significant population of red objects at z > 1. We select objects using the K_s band images, which reach an approximate AB magnitude limit K_s ≈ 22. We generate masks and derive completeness functions to characterize the sample. We have tested the quality of the photometry and photometric redshifts using both internal and external checks. Our final catalogue includes ≈95 000 sources down to K_s ≈ 22, with a significant tail towards high redshift. We have checked that there is a large sample of objects with spectral energy distributions that correspond to that of massive, passively evolving galaxies at z > 1, reaching as far as z ≈ 2.5. We have tested the possibility of combining our data with deep infrared observations at longer wavelengths, particularly Spitzer IRAC data.

Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics