ALHAMBRA Ks band selected catalogue

Galaxy formation and evolution are an essential part of astronomy and cosmology today. To better understand the processes that are involved in the mechanism behind them it is necessary to study the physical processes in the observable universe at different epochs, which requires large astronomical surveys. In the case of the ALHAMBRA Survey, near infrared images (NIR) provide extra information that significantly increases the scientific value of the data, particularly for strongly-reddened elliptical galaxies, AGN or moderate-redshift starburst galaxies. The selection in the optical band F814W (used for ALHAMBRA’s original catalogue in Molino et al. (2014)) creates a bias against intrinsically red galaxies that begins to be noticeable at z~0.8 and is dominant at z~1.1 as already noticed by Arnalte-Mur et al. (2014). In this thesis we present a new ALHAMBRA (Advanced Large, Homogeneous Area Medium Band Redshift Astronomical) catalogue selected in the NIR Ks-band. This new data set allows to extend the studies performed using the optical catalogue to higher redshift. The catalogue includes photometry for 94,182 sources distributed over seven fields and covering a total area of 2.47 deg2. We completed the catalogue with photometric redshifts computed using BPZ2.0 (Benitez 2000). We performed different tests to measure the accuracy of the photometry and the photometric redshifts. We also focused in this thesis on the measurement of the correlation function of red-type galaxies in the redshift range 0.75 < z < 1.45, extending the work performed in Hurtado-Gil et al. (2016). We used the same method described in Arnalte-Mur et al. (2014) to estimate the projected correlation function wp(rp). We have observed significant evolution of galaxy clustering in this redshift range and luminosity segregation at the highest redshift. In order to extend the photometry in the infrared wavelength range we cross-matched the ALHAMBRA Ks-selected catalogue with available Spitzer-IRAC public data and produced an additional ALHAMBRA-Ks+IRAC catalogue (AKs-IR). We included photometry in the ALHAMBRA Ks 20+3 filters, the synthetic F814W-band and the IRAC 3.6, 4.5 and 5.8 μm channels. The catalogue contains 36,024 sources in a total area of 0.93 deg2. We performed similar photometry and photometric tests as we had done with the Ks-band catalogue. In the final part of this thesis we have calculated the rest-frame Ks-band luminosity function (LF) using the data included in AKs-IR catalogue. We computed the LF using the method developed by López-Sanjuan et al. (2017). The comparison between our measurements and other similar works (Arnouts et al. 2005a; Cirasuolo et al. 2010; Mortlock et al. 2017) shows good agreement, especially with Cirasuolo et al. (2010). Finally, we analysed the redshift evolution of the parameters MKs★, φKs★ and α, together with the integrated Ks-band luminosity density jk. We find strong positive number evolution, coupled with no apparent luminosity evolution in the red population; whereas the blue population shows slight positive number evolution coupled with negative luminosity evolution. This results in a global population change, where blue galaxies dominate the luminosity density at z~2, and red galaxies dominate at z~0.5.Galaxy formation and evolution are an essential part of astronomy and cosmology today. To better understand the processes that are involved in the mechanism behind them it is necessary to study the physical processes in the observable universe at different epochs, which requires large astronomical surveys. In the case of the ALHAMBRA Survey, near infrared images (NIR) provide extra information that significantly increases the scientific value of the data, particularly for strongly-reddened elliptical galaxies, AGN or moderate-redshift starburst galaxies. The selection in the optical band F814W (used for ALHAMBRA’s original catalogue in Molino et al. (2014)) creates a bias against intrinsically red galaxies that begins to be noticeable at z~0.8 and is dominant at z~1.1 as already noticed by Arnalte-Mur et al. (2014). In this thesis we present a new ALHAMBRA (Advanced Large, Homogeneous Area Medium Band Redshift Astronomical) catalogue selected in the NIR Ks-band. This new data set allows to extend the studies performed using the optical catalogue to higher redshift. The catalogue includes photometry for 94,182 sources distributed over seven fields and covering a total area of 2.47 deg2. We completed the catalogue with photometric redshifts computed using BPZ2.0 (Benitez 2000). We performed different tests to measure the accuracy of the photometry and the photometric redshifts. We also focused in this thesis on the measurement of the correlation function of red-type galaxies in the redshift range 0.75 < z < 1.45, extending the work performed in Hurtado-Gil et al. (2016). We used the same method described in Arnalte-Mur et al. (2014) to estimate the projected correlation function wp(rp). We have observed significant evolution of galaxy clustering in this redshift range and luminosity segregation at the highest redshift. In order to extend the photometry in the infrared wavelength range we cross-matched the ALHAMBRA Ks-selected catalogue with available Spitzer-IRAC public data and produced an additional ALHAMBRA-Ks+IRAC catalogue (AKs-IR). We included photometry in the ALHAMBRA Ks 20+3 filters, the synthetic F814W-band and the IRAC 3.6, 4.5 and 5.8 μm channels. The catalogue contains 36,024 sources in a total area of 0.93 deg2. We performed similar photometry and photometric tests as we had done with the Ks-band catalogue. In the final part of this thesis we have calculated the rest-frame Ks-band luminosity function (LF) using the data included in AKs-IR catalogue. We computed the LF using the method developed by López-Sanjuan et al. (2017). The comparison between our measurements and other similar works (Arnouts et al. 2005a; Cirasuolo et al. 2010; Mortlock et al. 2017) shows good agreement, especially with Cirasuolo et al. (2010). Finally, we analysed the redshift evolution of the parameters MKs★, φKs★ and α, together with the integrated Ks-band luminosity density jk. We find strong positive number evolution, coupled with no apparent luminosity evolution in the red population; whereas the blue population shows slight positive number evolution coupled with negative luminosity evolution. This results in a global population change, where blue galaxies dominate the luminosity density at z~2, and red galaxies dominate at z~0.5

Photometric classification of QSOs from ALHAMBRA survey using random forest

Context: Given the current big data era in Astronomy, machine learning based methods have being applied over the last years to identify or classify objects like quasars, galaxies and stars from full sky photometric surveys. Aims: Here we systematically evaluate the performance of Random Forests (RF) in classifying quasars using either magnitudes or colours, both from broad and narrow-band filters, as features. Methods: The working data consists of photometry from the ALHAMBRA Gold Catalogue that we cross-matched with the Sloan Digital Sky Survey (SDSS) and with the Million Quasars Catalogue (Milliquas) for objects labelled as quasars, galaxies or stars. A RF classifier is trained and tested to evaluate the effect on final accuracy and precision of varying the free parameters and the effect of using narrow or broad-band magnitudes or colours. Results: Best performances of the classifier yielded global accuracy and quasar precision around 0.9. Varying model free parameters (within reasonable ranges of values) has no significant effects on the final classification. Using colours instead of magnitudes as features results in better performances of the classifier, especially using colours from the ALHAMBRA Survey. Colours that contribute the most to the classification are those containing the near-infrared $JHK$ bands.Comment: 7 pages including 6 figures and 3 tables. Accepted for publication in Astronomy and Astrophysic

Galaxy clusters and groups in the ALHAMBRA Survey

We present a catalogue of 348 galaxy clusters and groups with $0.2<z<1.2$ selected in the 2.78 $deg^2$ ALHAMBRA Survey. The high precision of our photometric redshifts, close to $1\%$, and the wide spread of the seven ALHAMBRA pointings ensure that this catalogue has better mass sensitivity and is less affected by cosmic variance than comparable samples. The detection has been carried out with the Bayesian Cluster Finder (BCF), whose performance has been checked in ALHAMBRA-like light-cone mock catalogues. Great care has been taken to ensure that the observable properties of the mocks photometry accurately correspond to those of real catalogues. From our simulations, we expect to detect galaxy clusters and groups with both $70\%$ completeness and purity down to dark matter halo masses of $M_h\sim3\times10^{13}\rm M_{\odot}$ for $z<0.85$. Cluster redshifts are expected to be recovered with $\sim0.6\%$ precision for $z<1$. We also expect to measure cluster masses with $\sigma_{M_h|M^*_{CL}}\sim0.25-0.35\, dex$ precision down to $\sim3\times10^{13}\rm M_{\odot}$, masses which are $50\%$ smaller than those reached by similar work. We have compared these detections with previous optical, spectroscopic and X-rays work, finding an excellent agreement with the rates reported from the simulations. We have also explored the overall properties of these detections such as the presence of a colour-magnitude relation, the evolution of the photometric blue fraction and the clustering of these sources in the different ALHAMBRA fields. Despite the small numbers, we observe tentative evidence that, for a fixed stellar mass, the environment is playing a crucial role at lower redshifts (z$<$0.5).Comment: Accepted for publication in MNRAS. Catalogues and figures available online and under the following link: http://bascaso.net46.net/ALHAMBRA_clusters.htm