Radio - Loud Active Galactic Nuclei from parsec to Mega-parsec scales

The thesis covers two subjects of extra-galactic astrophysics that concern radio-loud active galactic nuclei (RLAGNs). We describe the two subjects separately, but there are deep connections between the two. The first subject concerns the Mega-parsec scale environments of z~1-2 radio galaxies. First, we describe a method (Poisson probability method, PPM) primarily introduced to search for dense Megaparsec-scale environments (i.e. galaxy clusters and groups) around a specific beacon using photometric redshifts and galaxy number counts on the basis of Poisson statistics. We test the efficiency of our method of searching for cluster candidates against simulations. Two different approaches are adopted. (1) We use two z~1 X-ray detected cluster candidates found in the Cosmic Evolution Survey (COSMOS) and we shift them to higher redshift up to z = 2. We find that the PPM detects the cluster candidates up to z = 1.5, and it correctly estimates both the redshift and size of the two clusters. (2) We simulate spherically symmetric clusters of different size and richness, and we locate them at different redshifts (i.e., z = 1.0, 1.5, and 2.0) in the COSMOS field. We find that the PPM detects the simulated clusters within the z~1-2 range with a statistical 1-\u3c3 redshift accuracy of ~0.05. The PPM naturally arises as an effective mean field theory defined on the ensemble of the photometric redshift realizations of the galaxies in the field. A differential argument embedded in the PPM theory shows that the PPM partially overcomes the limitations deriving from low number-count statistics and shot-noise fluctuations. This is ultimately achieved through the use of a solid positional prior and an accurate photometric redshift sampling. Therefore, the PPM is an efficient alternative method for high-redshift cluster searches that may also be applied to both present and future wide field surveys such as SDSS Stripe 82, Large Synoptic Survey Telescope (LSST), and Euclid. Accurate photometric redshifts and a survey depth similar or better than that of COSMOS (e.g., I<25) are required. We also apply the PPM to search for high-redshift (z~1-2) galaxy clusters around low power radio galaxies (FR I). We use a sample of 32 FR Is within the COSMOS field from the Chiaberge et al. catalog that we redefine on the basis of the radio power. The sample redefinition allows us to estimate the comoving space density of sources with L_{1.4 GHz} 4510^32.3 erg s^{-1} Hz^{-1} at z 451.1, which strengthens the case for a strong cosmological evolution of these sources. Overdensities are found around ~70% of the FR Is. This rate is in agreement with the fraction found for low redshift FR Is and it is significantly higher than that for FR IIs at all redshifts. Cluster candidates found with our method are excellent targets for next generation space telescopes such as James Webb Space Telescope (JWST). The method reveals itself as a powerful tool to search for distant galaxy clusters. The second subject that concerns RLAGNs is focused on blazars. We build a complete sample of flat-spectrum radio quasars (FSRQs) from the WMAP 7-yr catalog and compare black hole mass estimates based on fitting a standard accretion disk model to the `blue bump' with those obtained from the commonly used single-epoch virial method. The sample comprises 80 objects flux limited at 1 Jy at 23 GHz, 55 of which (69%) have a clearly detected `blue bump'. Thirty-three of the 55 FSRQs have, in the literature, black hole mass estimates obtained with the virial method. The mass estimates obtained from the two methods are well correlated. The fact that the two totally independent methods agree so closely in spite of all the potentially large uncertainties associated with each of them lends strong support to both of them. We find evidence of mid-infrared (MIR) emitting active galactic nucleus (AGN) torus in the spectral energy distributions (SEDs) of seven of the 55 FSRQs with evidence of blue bump and an uncertain indication is found for one more. The fraction of FSRQs with evidence of AGN torus increases up to 39% if only the FSRQs at z 641 and with evidence of blue bump are considered. Our results suggest that the detection of the AGN torus is favored in those FSRQs where the specific synchrotron flux at MIR wavelengths does not overwhelm the contribution from the torus. Conversely to BL Lac sources, which are known to lack much sign of gas, our results show that the AGN torus might be present in a large fraction of FSRQs

Enabling strategies that influence on educational and occupational choices of visually impaired adolescents

In this work we present some of the results of the doctoral thesis: “Guidance and visual impairment. Factors that influence the adolescent choices, linked with the investigation: “Evaluation of inclusion strategies to reduce university dropout and reorientation in other educational-training areas”.** (Gavilán, 2014-2017 cód. S035). In this regard we investigated factors that guide the educational and occupational choices of adolescents and young people with visual impairment: blind people, deeply and mild visually impaired, who were completing high school. It is a part of the Theoretical Operational Model (Gavilán 2006, 2017), and takes into account the Diversity of Disability Model and the current perspectives about the visual impairment. In this work we’ll present some of the results got through 22 visually impaired participants by means of two modalities of the theoretical model adopted: the Specific Individual Process and the Micro-process. Three key findings have been reached. At first place, we’ve found the influence of the subjective perspective of people themselves in front of their visual impairment as a prevailing factor in their choices, emphasized or moderate, according their family perspective. In second place, the similarity of the source factors of educational/occupational choices among sighted and visually impaired people, but influenced by their disability condition. Finally, we’ve found the deficiency/unsuitability of the guidance processes.Facultad de Psicologí

Enabling strategies that influence on educational and occupational choices of visually impaired adolescents

In this work we present some of the results of the doctoral thesis: “Guidance and visual impairment. Factors that influence the adolescent choices, linked with the investigation: “Evaluation of inclusion strategies to reduce university dropout and reorientation in other educational-training areas”.** (Gavilán, 2014-2017 cód. S035). In this regard we investigated factors that guide the educational and occupational choices of adolescents and young people with visual impairment: blind people, deeply and mild visually impaired, who were completing high school. It is a part of the Theoretical Operational Model (Gavilán 2006, 2017), and takes into account the Diversity of Disability Model and the current perspectives about the visual impairment. In this work we’ll present some of the results got through 22 visually impaired participants by means of two modalities of the theoretical model adopted: the Specific Individual Process and the Micro-process. Three key findings have been reached. At first place, we’ve found the influence of the subjective perspective of people themselves in front of their visual impairment as a prevailing factor in their choices, emphasized or moderate, according their family perspective. In second place, the similarity of the source factors of educational/occupational choices among sighted and visually impaired people, but influenced by their disability condition. Finally, we’ve found the deficiency/unsuitability of the guidance processes.Facultad de Psicologí

Enabling strategies that influence on educational and occupational choices of visually impaired adolescents

In this work we present some of the results of the doctoral thesis: “Guidance and visual impairment. Factors that influence the adolescent choices, linked with the investigation: “Evaluation of inclusion strategies to reduce university dropout and reorientation in other educational-training areas”.** (Gavilán, 2014-2017 cód. S035). In this regard we investigated factors that guide the educational and occupational choices of adolescents and young people with visual impairment: blind people, deeply and mild visually impaired, who were completing high school. It is a part of the Theoretical Operational Model (Gavilán 2006, 2017), and takes into account the Diversity of Disability Model and the current perspectives about the visual impairment. In this work we’ll present some of the results got through 22 visually impaired participants by means of two modalities of the theoretical model adopted: the Specific Individual Process and the Micro-process. Three key findings have been reached. At first place, we’ve found the influence of the subjective perspective of people themselves in front of their visual impairment as a prevailing factor in their choices, emphasized or moderate, according their family perspective. In second place, the similarity of the source factors of educational/occupational choices among sighted and visually impaired people, but influenced by their disability condition. Finally, we’ve found the deficiency/unsuitability of the guidance processes.Facultad de Psicologí

Galaxy Clusters around z~1-2 Low Luminosity Radio Galaxies

At variance with powerful radio galaxies Low Luminosity Radio Galaxies (LLRGs) are almost invariably found in clusters and often associated with the brightest cluster galaxies, at least at low-redshifts. In order to prove that this holds also at high-z we exploit a sample of 32 LLRGs at z~1-2 drawn from the COSMOS survey and search for Mpc-scale overdensities using photometric redshifts and our recently developed Poisson Probability Method. We find that ~70% of the LLRGs reside in rich groups or clusters. This fraction is higher than that found for powerful radio galaxies at similar redshifts and is in excellent agreement with results obtained at low redshifts. Independent confirmation of some of our cluster candidates is found in catalogs of clusters selected in X-rays or spectroscopically. Our strategy is unbiased with respect to colors and star formation history of cluster galaxies and represents a valuable alternative to conventional methods that search for clusters. We observed with the 30 mt. IRAM telescope two of our z=1 LLRGs in clusters to search for molecular gas and set CO upper limits. Our clusters are optimal targets for mm-obsevations with NOEMA and ALMA

Time delays between Fermi LAT and GBM light curves of GRBs

Most Gamma-Ray Bursts (GRBs) detected by the Fermi Gamma-ray Space Telescope exhibit a delay of up to about 10 seconds between the trigger time of the hard X-ray signal as measured by the Fermi GBM and the onset of the MeV-GeV counterpart detected by the LAT. This delay may hint at important physics, whether it is due to the intrinsic variability of the inner engine or it is related to quantum dispersion effects in the velocity of light propagation from the sources to the observer. It is critical to have a proper assessment of how these time delays affect the overall properties of the light curves. We cross-correlated the 5 brightest GRBs of the 1st Fermi LAT Catalog by means of the continuous correlation function (CCF) and of the Discrete Correlation Function (DCF). A maximum in the DCF suggests the presence of a time lag between the curves, whose value and uncertainty are estimated through a Gaussian fitting of the DCF profile and light curve simulation via a Monte Carlo approach. The cross-correlation of the observed LAT and GBM light curves yields time lags that are mostly similar to those reported in the literature, but they are formally consistent with zero. The cross-correlation of the simulated light curves yields smaller errors on the time lags and more than one time lag for GRBs 090902B and 090926A; for all 5 GRBs, the time lags are significantly different from zero and consistent with those reported in the literature, when only the secondary maxima are considered for those two GRBs. The DCF method evidences the presence of time lags between the LAT and GBM light curves and underlines their complexity. While this suggests that the delays should be ascribed to intrinsic physical mechanisms, more sensitivity and larger statistics are needed to assess whether time lags are universally present in the early GRB emission and which dynamical time scales they trace.Comment: 9 pages, 3 figures, accepted for publication in Astronomy & Astrophysic

Bright submillimeter galaxies do trace galaxy protoclusters

There is controversy whether dusty starbursts selected at submillimeter wavelengths can trace galaxy overdensities. We perform the first systematic search for protoclusters around a homogeneously selected sample of 12 spectroscopically confirmed submillimeter galaxies (SMGs) at $z\sim1.2-5.3$ in the GOODS-N field. We applied the Poisson Probability Method (PPM) to search for Mpc scale overdensities around these SMGs using three photometric redshift catalogs. We detect galaxy overdensities for 11 out of the 12 SMGs ($92\%\pm8$\%), distributed over eight protoclusters. We confirm three previously discovered protoclusters, and we detect five new ones around the SMGs SMMJ123634 ($z=1.225$), ID.19 ($z=2.047$), SMMJ123607 ($z=2.487$), SMMJ123606 ($z=2.505$), and GN10 ($z=5.303$). A wavelet-based analysis shows that the SMGs live in protocluster cores with a complex morphology (compact, filamentary, or clumpy) and an average size of $\sim(0.4-1)$Mpc. By comparing the PPM results obtained using independently the three redshift catalogs, we possibly witness a transitioning phase at $z\gtrsim4$ for the galaxy populations. While $z\lesssim4$ protoclusters appear to be populated by dusty galaxies, those at highest redshifts $z\sim5$ are detected as overdensities of Lyman$\alpha$ emitters or Lyman break galaxies. We also find a good correlation between the molecular (H$_2$) gas mass of the SMG and the overdensity significance. To explain the overall phenomenology, we suggest that galaxy interactions in dense environments likely triggered the starburst and gas-rich phase of the SMGs. Altogether, we support the scenario that SMGs are excellent tracers of distant protoclusters. Those presented in this work are excellent targets for the {\it James Webb Space Telescope.} Surveys with forthcoming facilities (e.g., {\it Euclid}, LSST) can be tuned to detect even larger samples of distant protoclusters.Comment: 22 pages, Astronomy & Astrophysics in press. HTML files of Figure 3 are available at https://obswww.unige.ch/~castigna/Figure3_html

Black hole and galaxy co-evolution in radio-loud AGN at z ~ 0.3-4

There exists a well known relation between the mass of the supermassive black hole (SMBH) in the center of galaxies and their bulge mass or central velocity dispersion. This suggests a co-evolution between SMBH and their galaxy hosts. Our aim is to study this relation specifically for radio loud galaxies, and as a function of redshift $z$. We selected a sample of radio-galaxies and AGN by cross-matching the low radio frequency sources from VLA FIRST with spectroscopically confirmed sources from wide field surveys including SDSS DR14 ugriz and DES DR2 grzY in optical, WISE in infrared, and the Galaxy And Mass Assembly (GAMA) spectroscopic survey. Keeping only high signal to noise (S/N) sources in WISE magnitudes, and those with broad emission lines, we selected a sub sample of 42 radio sources, all with infrared-to-optical counterparts, for which we characterized the stellar, star formation, and black hole properties. We estimated the central SMBH mass, the stellar mass $M_\star$, the Eddington ratio $\eta$ and the jet power, $Q_{\rm jet}$. The relation between SMBH mass, $M_\star$, $\eta$ and $z$ are put into context by comparing them with scaling relations ($M_{\rm BH}$--$M_{\star}$, $M_{\rm BH}/M_\star$--$z$, $M_{\rm BH}$--$Q_{\rm jet}$ and $Q_{\rm jet}$--$\eta$) from the literature. An evolutionary scenario where radio-mode AGN feedback (or the cluster environments) regulate the accretion onto the SMBHs and the stellar mass assembly of the radio sources is discussed, which may explain the observed phenomenology, and in particular the presence of radio sources with high $M_{\rm BH}/M_\star$ ratios. This pilot study represents a benchmark for future ones using wide field surveys such as Euclid and the Vera Rubin telescope.Comment: 15 pages, 7 figures, version after the proof corrections, A&A in pres

Educational guidance strategies in the case of undergraduate pupils of student mobility

This work attends to identify and characterize the educational guidance strategies in the case of undergraduate pupils of student mobility. Although there are wide national and international backgrounds related to guidance, investigations on educational guidance in the case here considered are considerably few. In our context we can take into account a growing increase of students who decide to study undergraduate degree at national universities, which leads to the need to develop guidance intervention strategies that accompany and promote their educational histories. In this work at first place we describe the backgrounds and characteristics of the student mobility at the Psychology School of the National University of La Plata (2007-2017), from the systematization and analysis of institutional documentary sources. Secondly, the educational guidance actions implemented with students who studied subjects in the second semester of the 2017 school year are specifically analyzed. For this purpose, a semi-structured interview was designed and implemented, organized in different axes, which was applied to the aforementioned students. Finally, results are discussed and intervention strategies are proposed that consider institutions and significant actors for student mobility processes at the university level.Facultad de Psicologí