Alejandro Borlaff

Alejandro Borlaff

Publications

The missing light of the Hubble Ultra Deep Field

Published in Astronomy & Astrophysics, 2019

In this work we present ABYSS, a new reduction of the near-infrared observations of the Hubble Ultra Deep Field with the WFC3/IR of the Hubble Space Telescope. As a result, we successfully recover the outskirts of galaxies, increasing the depth of the HUDF by reducing the systematic biases. This new version of the HUDF recovers the light around massive galaxies to an unprecedented detail. We conclude that these methods can be highly beneficial for many future space missions, such as JWST and Euclid.

Recommended citation: Borlaff, A. (2019). "The missing light of the Hubble Ultra Deep Field. " Astronomy & Astrophysics . 1(1). https://www.aanda.org/articles/aa/pdf/2019/01/aa34312-18.pdf

Evolution of the anti-truncated stellar profiles of S0 galaxies since z = 0.6 in the SHARDS survey. II. Structural and photometric evolution.

Published in Astronomy & Astrophysics, 2018

In this paper we analyse the photometric and structural properties of the first sample of lenticular galaxies with Type-III profiles obtained in Borlaff et al. (2017), corrected for PSF effects, beyond the local Universe (at 0.2 < z < 0.6). We found that the general structure of Type-III S0 galaxies does not present a significant change, although they do show a brightness dimming of ∼1.5 magnitudes since z∼0.6. These observations pose strong constraints to the proposed evolutionary models of this type of galaxies, ruling out high-redshift monolithic collapse as the main scenario for the formation of Type-III S0 galaxies.

Recommended citation: Borlaff, A. (2018). "Evolution of the anti-truncated stellar profiles of S0 galaxies since z = 0.6 in the SHARDS survey. II. Structural and photometric evolution." Astronomy & Astrophysics. https://arxiv.org/pdf/1803.00570.pdf

Evolution of the anti-truncated stellar profiles of S0 galaxies since z = 0.6 in the SHARDS survey. I. Sample and methods

Published in Astronomy & Astrophysics, 2017

During my PhD, following up the work presented in Masters thesis, we identified a sample of anti-truncated S0 galaxies beyond the local Universe, using HST/ACS GOODS-North cosmological field images. We found that despite the high spatial resolution of HST, the point spread function (PSF) can distort the structure of the outskirts of galaxies. To avoid this effect, we deconvolved each object using a dedicated hybrid PSF model of the ACS camera of HST. We identified 14 Type-III S0 galaxies between 0.2 < z < 0.6 (Borlaff et al. 2017), which is the furthest sample of this type of galaxies up-to-date.

Recommended citation: Borlaff et al. (2017). "Evolution of the anti-truncated stellar profiles of S0 galaxies since z = 0.6 in the SHARDS survey. I. Sample and methods " A&A. https://www.aanda.org/articles/aa/pdf/2017/08/aa30282-16.pdf

Type-II surface brightness profiles in edge-on galaxies produced by flares

Published in Astronomy & Astrophysics, 2016

As part of my PhD project, we studied the effects of the increase of the stellar disc scale-height with radius (or flaring) on the surface brightness profiles of edge-on disc galaxies (Borlaff et al. 2016). This phenomenon has been detected in the stellar discs of simulated and real galaxies, including the Milky Way. Using realistic 3D models based on observations we demonstrated that flares can create down-bending surface brightness profiles when observed at high inclinations. Contrarily, flares have no effect on the profiles of face-on galaxies, partially explaining the relatively high abundances of Type-II breaks in edge-on galaxies. We found that the morphology of the discs with flares match the observations of real breaks, which were previously associated with radial star formation thresholds Martin-Navarro et al. (2012). In addition, we demonstrate that flares can explain the weakening of the breaks with increasing vertical distance from the galactic plane found by Pohlen et al. (2007) and Martinez-Lombilla et al. (2018). Following the results from this article, we were granted with an ultra-deep observation program with OSIRIS/GTC at La Palma Observatory for three edge-on galaxies (PID: 80-GTC61/18B), to detect possible flares, warps, satellites and stellar haloes in the outskirts of the target galaxies. The observations will allow us to obtain the surface brightness and stellar mass profiles down to 31 mag arcsec^2 in the g-band and 30.5 in the r-band (3 sigma in 10x10 arcsec^2 boxes).

Recommended citation: Borlaff et al. (2016). "Type-II surface brightness profiles in edge-on galaxies produced by flares " A&A. https://www.aanda.org/articles/aa/pdf/2016/07/aa28868-16.pdf