Forward Modeling of Spectroscopic Galaxy Surveys: Application to SDSS

Galaxy spectra are essential to probe the spatial distribution of galaxies in our Universe. To better interpret current and future spectroscopic galaxy redshift surveys, it is important to be able to simulate these data sets. We describe Uspec, a forward modeling tool to generate galaxy spectra taking into account some intrinsic galaxy properties as well as instrumental responses of a given telescope. The model for the intrinsic properties of the galaxy population, i.e., the luminosity functions, and size and spectral coefficients distribu- tions, was developed in an earlier work for broad-band imaging surveys [1], and we now aim to test the model further using spectroscopic data. We apply Uspec to the SDSS/CMASS sample of Luminous Red Galaxies (LRGs). We construct selection cuts that match those used to build this LRG sample, which we then apply to data and simulations in the same way. The resulting real and simulated average spectra show a good statistical agreement overall, with residual differences likely coming from a bluer galaxy population of the simulated sam- ple. We also do not explore the impact of non-solar element ratios in our simulations. For a quantitative comparison, we perform Principal Component Analysis (PCA) of the sets of spectra. By comparing the PCs constructed from simulations and data, we find good agree- ment for all components. The distributions of the eigencoefficients also show an appreciable overlap. We are therefore able to properly simulate the LRG sample taking into account the SDSS/BOSS instrumental responses. The differences between the two samples can be ascribed to the intrinsic properties of the simulated galaxy population, which can be reduced by further improvements of our modelling method in the future. We discuss how these results can be useful for the forward modeling of upcoming large spectroscopic surveys.Comment: 32 pages, 14 figures, accepted by JCA

Uno studio sulle caratteristiche di un campione di pazienti internati presso l'Ospedale Psichiatrico Giudiziario di Castiglione delle Stiviere e dimessi nella regione Lazio.

Aim. The aim of this study was: i) To identify socio-demographic and clinical data in a sample of inmates in the Criminal Mental Hospital (CMH) at Castiglione delle Stiviere; ii) to assess the presence of characteristics which could foresee the commission of a crime of psychiatric interest; iii) to assess the frequency of crime repetition. Materials and Methods. This study was carried out on a sample of 38 patients. A descriptive analysis of the sample was carried out and the associations among several variables were analyzed. Results. The sample is characterized by a high frequency of schizophrenia diagnosis (73.0%), the presence of hospitalization before the commission of the crime (68.4%) and the absence of criminal precedents (71.1%). For men the age of the commission of the crime is equal to 33.72±10.6 years and for women to 45.18±11.4 years (p=0.011). The time between the onset and the commission of the crime is longer in patients who have received therapy (treatment) than in those ones with no treatment (p=0.012). About 12% of the sample committed new crimes. Conclusions. The results showed previous criminal acts are not predictive for the commission of new crimes of psychiatric interest. However many patients had previous contacts with community facilities before their first admission to hospital and the treatment extended the interval between the onset of the disease and the commission of the crime. The relapse rate after the discharge was very low if compared with samples coming from other services that offered more custodial rather than rehabilitative facilities

Dalla crisi del paradigma neokraepeliniano verso una nuova nosografia psichiatrica. Il DSM-5.

With this article we intend to outline the story of American psychiatry starting at the end of the 19th century until the present time, describing the cultural, political and economic context which culminated in the development and diffusion of biological psychiatry and its nosography. The diffusion of psychoanalysis and of A. Meyer’s psychological psychiatry, beginning at the end of the Second World War until the end of the Sixties, determined such as an enlargement of psychiatric diagnosis which no longer allowed one to distinguish a sane individual from an ill individual. This “dimensional” model caused a slow process of de-medicalization of psychiatry which removed consent and legitimacy from the discipline. The answer was the publication in 1980 of DSM III, the work of a small number of psychiatrists known as the “Neo-Kraepelinians”. The new nosography based on a categorial diagnostic system, emphasized what is directly observable and therefore measurable, and not what is clinically significant. Whit DSM III and the successive versions the interest of the psychiatrists moved from the clinical to the epidemiological research. In the attempt to take psychiatry back to one of the medical sciences DSM III has in reality continued the process of undermining started whit Meyer and psychoanalysis. And now with the forthcoming publication of DSM V, psychiatry will be confused ever more with neurosciences

Spectro-imaging forward model of red and blue galaxies

For the next generation of spectroscopic galaxy surveys, it is important to forecast their performances and to accurately interpret their large data sets. For this purpose, it is necessary to consistently simulate different populations of galaxies, in particular Emission Line Galaxies (ELGs), less used in the past for cosmological purposes. In this work, we further the forward modeling approach presented in Fagioli et al. 2018, by extending the spectra simulator USPEC to model galaxies of different kinds with improved parameters from Tortorelli et al. 2020. Furthermore, we improve the modeling of the selection function by using the image simulator UFIG. We apply this to the Sloan Digital Sky Survey (SDSS), and simulate similar to 157, 000 multi-band images. We pre-process and analyse them to apply cuts for target selection, and finally simulate SDSS/BOSS DR14 galaxy spectra. We compute photometric, astrometric and spectroscopic properties for red and blue, real and simulated galaxies, finding very good agreement. We compare the statistical properties of the samples by decomposing them with Principal Component Analysis (PCA). We find very good agreement for red galaxies and a good, but less pronounced one, for blue galaxies, as expected given the known difficulty of simulating those. Finally, we derive stellar population properties, mass-to-light ratios, ages and metallicities, for all samples, finding again very good agreement. This shows how this method can be used not only to forecast cosmology surveys, but it is also able to provide insights into studies of galaxy formation and evolution.ISSN:1475-751

Measurement of the B-band galaxy Luminosity Function with Approximate Bayesian Computation

The galaxy Luminosity Function (LF) is a key observable for galaxy formation, evolution studies and for cosmology. In this work, we propose a novel technique to forward model wide-field broad-band galaxy surveys using the fast image simulator UFig and measure the LF of galaxies in the B-band. We use Approximate Bayesian Computation (ABC) to constrain the galaxy population model parameters of the simulations and match data from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). We define a number of distance metrics between the simulated and the survey data. By exploring the parameter space of the galaxy population model through ABC to find the set of parameters that minimize these distance metrics, we obtain constraints on the LFs of blue and red galaxies as a function of redshift. We find that M* fades by Δ M*0.1−1.0,b = 0.68 ± 0.52 and Δ M*0.1−1.0,r = 0.54 ± 0.48 magnitudes between redshift z = 1 and z = 0.1 for blue and red galaxies, respectively. We also find that phgr* for blue galaxies stays roughly constant between redshift z = 0.1 and z=1, while for red galaxies it decreases of ~ 35%. We compare our results to other measurements, finding good agreement at all redshifts, for both blue and red galaxies. To further test our results, we compare the redshift distributions for survey and simulated data. We use the spectroscopic redshift distribution from the VIMOS Public Extragalactic Redshift Survey (VIPERS) and we apply the same selection in colours and magnitudes on our simulations. We find a good agreement between the survey and the simulated redshift distributions. We provide best-fit values and uncertainties for the parameters of the LF. This work offers excellent prospects for measuring other galaxy population properties as a function of redshift using ABC. © 2020 IOP Publishing Ltd. and Sissa Medialab.ISSN:1475-751

How elevated is the dynamical-to-stellar mass ratio of the ultracompact dwarf S999?

Here we present new Keck ESI high-resolution spectroscopy and deep archival HST/ACS imaging for S999, an ultra-compact dwarf in the vicinity of M87, which was claimed to have an extremely high dynamical-to-stellar mass ratio. Our data increase the total integration times by a factor of 5 and 60 for spectroscopy and imaging, respectively. This allows us to constrain the stellar population parameters for the first time (simple stellar population equivalent age $=7.6^{+2.0}_{-1.6}$ Gyr; $[Z/\textrm{H}]=-0.95^{+0.12}_{-0.10}$; $[\alpha/\textrm{Fe}]=0.34^{+0.10}_{-0.12}$). Assuming a Kroupa stellar initial mass function, the stellar population parameters and luminosity ($M_{F814W}=-12.13\pm0.06$ mag) yield a stellar mass of $M_*=3.9^{+0.9}_{-0.6}\times10^6 M_{\odot}$, which we also find to be consistent with near-infrared data. Via mass modelling, with our new measurements of velocity dispersion ($\sigma_{ap}=27\pm2$ km s$^{-1}$) and size ($R_e=20.9\pm1.0$ pc), we obtain an elevated dynamical-to-stellar mass ratio $M_{dyn}/M_*=8.2$ (with a range $5.6\le M_{dyn}/M_* \le 11.2$). Furthermore, we analyse the surface brightness profile of S999, finding only a small excess of light in the outer parts with respect to the fitted S\'ersic profile, and a positive colour gradient. Taken together these observations suggest that S999 is the remnant of a much larger galaxy that has been tidally stripped. If so, the observed elevated mass ratio may be caused by mechanisms related to the stripping process: the existence of an massive central black hole or internal kinematics that are out of equilibrium due to the stripping event. Given the observed dynamical-to-stellar mass ratio we suggest that S999 is an ideal candidate to search for the presence of an overly massive central black hole.Comment: 16 pages, 5 figures, accepted for publication in MNRA