Galaxy Peculiar Velocities and Infall onto Groups

We perform statistical analyses to study the infall of galaxies onto groups and clusters in the nearby Universe. The study is based on the UZC and SSRS2 group catalogs and peculiar velocity samples. We find a clear signature of infall of galaxies onto groups over a wide range of scales 5 h^{-1} Mpc<r<30 h^{-1} Mpc, with an infall amplitude on the order of a few hundred kilometers per second. We obtain a significant increase in the infall amplitude with group virial mass (M_{V}) and luminosity of group member galaxies (L_{g}). Groups with M_{V}<10^{13} M_{\odot} show infall velocities V_{infall} \simeq 150 km s^{-1} whereas for M_{V}>10^{13} M_{\odot} a larger infall is observed, V_{infall} \simeq 200 km s^{-1}. Similarly, we find that galaxies surrounding groups with L_{g}<10^{15} L_{\odot} have V_{infall} \simeq 100 km s^{-1}, whereas for L_{g}>10^{15} L_{\odot} groups, the amplitude of the galaxy infall can be as large as V_{infall} \simeq 250 km s^{-1}. The observational results are compared with the results obtained from mock group and galaxy samples constructed from numerical simulations, which include galaxy formation through semianalytical models. We obtain a general agreement between the results from the mock catalogs and the observations. The infall of galaxies onto groups is suitably reproduced in the simulations and, as in the observations, larger virial mass and luminosity groups exhibit the largest galaxy infall amplitudes. We derive estimates of the integrated mass overdensities associated with groups by applying linear theory to the infall velocities after correcting for the effects of distance uncertainties obtained using the mock catalogs. The resulting overdensities are consistent with a power law with \delta \sim 1 at r \sim 10 h^{-1}Mpc.Comment: 25 pages, 10 figure

Low X-Ray Luminosity Galaxy Clusters: Main goals, sample selection, photometric and spectroscopic observations

We present the study of nineteen low X-ray luminosity galaxy clusters (L$_X \sim$ 0.5--45 $\times$ $10^{43}$ erg s$^{-1}$), selected from the ROSAT Position Sensitive Proportional Counters (PSPC) Pointed Observations (Vikhlinin et al. 1998) and the revised version of Mullis et al. (2003) in the redshift range of 0.16 to 0.7. This is the introductory paper of a series presenting the sample selection, photometric and spectroscopic observations and data reduction. Photometric data in different passbands were taken for eight galaxy clusters at Las Campanas Observatory; three clusters at Cerro Tololo Interamerican Observatory; and eight clusters at the Gemini Observatory. Spectroscopic data were collected for only four galaxy clusters using Gemini telescopes. With the photometry, the galaxies were defined based on the star-galaxy separation taking into account photometric parameters. For each galaxy cluster, the catalogues contain the PSF and aperture magnitudes of galaxies within the 90\% completeness limit. They are used together with structural parameters to study the galaxy morphology and to estimate photometric redshifts. With the spectroscopy, the derived galaxy velocity dispersion of our clusters ranged from 507 km~s$^{-1}$ for [VMF98]022 to 775 km~s$^{-1}$ for [VMF98]097 with signs of substructure. Cluster membership has been extensively discussed taking into account spectroscopic and photometric redshift estimates. In this sense, members are the galaxies within a projected radius of 0.75 Mpc from the X-ray mission peak and with cluster centric velocities smaller than the cluster velocity dispersion or 6000 km~s$^{-1}$, respectively. These results will be used in forthcoming papers to study, among the main topics, the red cluster sequence, blue cloud and green populations; the galaxy luminosity function and cluster dynamics.Comment: 13 pages, 6 tables, 9 figures. Uses emulateapj. Accepted for publication in The Astronomical Journal. Some formatting errors fixe

Leiomyosarcoma of the Larynx: A Complex Diagnosis

An 84-year-old man was referred to our institution for dysphonia present for 2 months. Fiberoptic laryngoscopy demonstrated a polypoid lesion of the right true vocal fold with normal motility. Excisional biopsy of a submucosal thickening of the right vocal fold with vocal ligament calcification was performed. Histology revealed squamous cell epithelium without malignancy. Postoperative endoscopic follow-up was regular. Six months after surgery, dysphonia and dyspnea occurred. Flexible laryngoscopy demonstrated right hemilaryngeal paralysis, edema, and partial airway obstruction. Necrotic tissue and purulent secretions were visible at the anterior commissure, right vocal fold, and ipsilateral vestibule. A second microlaryngoscopic surgery included multiple biopsies and debridement of the necrotic tissue. Histological report was negative for malignancy, and purulent chondritis was diagnosed. Intravenous antibiotic therapy was administered with improvement of infection, inflammation, dysphonia, and dyspnea. The patient was discharged

Grupos de galaxias: dependencia de las propiedades de sus galaxias miembros con la emisión en radio

We present a study of the observational properties of Galaxies in Groups and its AGN host galaxies. We analyze the characteristics of the emision from the host AGN galaxies, both in the optical region as in the radio frecuencies, and its relation with their environment. In order to make these studies, the information from AGN associated with galaxy clusters has been correlated to the FIRST radio survey. In this correlation we analyze the parameters of these galaxies: luminosity, morphology, stellar mass, stellar age, etc.Fil: Nieto, L.. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Coldwell Lloveras, Georgina Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Valotto, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentin

The VVV near-IR galaxy catalogue in a Northern part of the Galactic disc

The automated identification of extragalactic objects in large surveys provides reliable and reproducible samples of galaxies in less time than procedures involving human interaction. However, regions near the Galactic disc are more challenging due to the dust extinction. We present the methodology for the automatic classification of galaxies and non-galaxies at low Galactic latitude regions using both images and, photometric and morphological near-IR data from the VVVX survey. Using the VVV-NIRGC, we analyse by statistical methods the most relevant features for galaxy identification. This catalogue was used to train a CNN with image data and an XGBoost model with both photometric and morphological data and then to generate a dataset of extragalactic candidates. This allows us to derive probability catalogues used to analyse the completeness and purity as a function of the configuration parameters and to explore the best combinations of the models. As a test case, we apply this methodology to the Northern disc region of the VVVX survey, obtaining 172,396 extragalatic candidates with probabilities of being galaxies. We analyse the performance of our methodology in the VVV disc, reaching an F1-score of 0.67, a 65 per cent purity and a 69 per cent completeness. We present the VVV-NIR Galaxy Catalogue: Northern part of the Galactic disc comprising 1,003 new galaxies, with probabilities greater than 0.6 for either model, with visual inspection and with only 2 previously identified galaxies. In the future, we intend to apply this methodology to other areas of the VVVX survey.Comment: 12 pages, 14 figures, accepted in MNRA

Analysis of candidates for interacting galaxy clusters: I. A1204 and A2029/A2033

Merging galaxy clusters allow for the study of different mass components, dark and baryonic, separately. Also, their occurrence enables to test the ΛCDM scenario, which can be used to put constraints on the selfinteracting cross-section of the dark-matter particle. It is necessary to perform a homogeneous analysis of these systems. Hence, based on a recently presented sample of candidates for interacting galaxy clusters, we present the analysis of two of these cataloged systems. In this work, the first of a series devoted to characterizing galaxy clusters in merger processes, we perform a weak lensing analysis of clusters A1204 and A2029/2033 to derive the total masses of each identified interacting structure together with a dynamical study based on a two-body model. We also describe the gas and the mass distributions in the field through a lensing and an X-ray analysis. This is the first of a series of works which will analyze these type of system in order to characterize them. Neither merging cluster candidate shows evidence of having had a recent merger event. Nevertheless, there is dynamicalevidence that these systems could be interacting or could interact in the future. It is necessary to include more constraints in order to improve the methodology of classifying merging galaxy clusters.Characterization of these clusters is important in order to properly understand the nature of these systems and their connection withdynamical studies.Fil: Gonzalez, Elizabeth Johana. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: de Los Rios, Martín Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Oio, Gabriel Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Hernández Lang, Daniel. Universidad de La Serena; ChileFil: AguirreTagliaferro, Tania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Dominguez Romero, Mariano Javier de Leon. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Nilo Castellon, Jose Luis Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentina. Universidad de la Serena; ChileFil: Cuevas L., H.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Valotto, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentin

The V-band luminosity function of galaxies in A2151

We present a wide field $V$-band imaging survey of approximately 1 deg$^2$ ($\sim7.2 h^{-2}_{75}$ Mpc$^{2}$) in the direction of the nearby cluster of galaxies Abell 2151 (the Hercules Cluster). The data are used to construct the luminosity function (LF) down to $M_V \approx -14.85$, thus allowing us to study the dwarf galaxy population in A2151 for the first time. The obtained global LF is well described by a Schechter function with best-fit parameters $\alpha = -1.29^{+0.09}_{-0.08}$ and $M_V^* = -21.41^{+0.44}_{-0.41}$. The radial dependence of the LF was investigated, with the faint-end slope tending to be slightly steeper in the outermost regions and farther away than the virial radius. Given the presence of significant substructure within the cluster, we also analysed the LFs in three different regions. We find that the dwarf to giant ratio increases from the northern to the southern subcluster, and from low to high local density environments, although these variations are marginally significant (less than 2$\sigma$).Comment: Accepted for publication in A&

Faint galaxy population in clusters: X-ray emission, cD halos and projection effects

We analyze samples of nearby clusters taken from the Abell catalog and the X-ray Sample of Bright Clusters(De Grandi et al 1999) including a wide range of X-ray luminosities.Using the usually adopted background subtraction procedures, we find that galaxies in clusters selected by means of their X-ray emission show a flat luminosity function (faint end slope $\alpha \simeq -1.1$) consistent with that derived for galaxies in the field and groups. By contrast, the sample of Abell clusters that do not have an X-ray counterpart shows a galaxy luminosity function with a steep faint end ($\alpha \simeq -1.6$). We investigate the possibility that cD halos could be formed by the disruption of galaxies in rich relaxed clusters that show an apparently flat faint end galaxy luminosity function (Lopez-Cruz et al 1997). We find that clusters dominated by a central cD galaxy (Bautz-Morgan classes I and II) show the same systematic trend: X-ray selected clusters have flatter faint end slopes than those clusters with no detected X-ray emission. Thus, it is likely the X-ray selection and not the cluster domination by central galaxies what correlates with background decontamination estimates of the galaxy luminosity function. Moreover, no significant correlation between X-ray luminosity and the galaxy LF faint end slope is found. These results do not support a scenario where flat faint end slopes are a consequence of cD formation via the disruption of faint galaxies. We argue that the clusters without X-ray emission are strongly affected by projection effects which give rise to spurious faint end slopes estimated using background subtraction procedures (Valotto et al 2001).Comment: Accepted for publication in ApJ (vol. 601

Gemini Observations of Galaxies in Rich Early Environments (GOGREEN) I : survey description.

We describe a new Large Program in progress on the Gemini North and South telescopes: Gemini Observations of Galaxies in Rich Early Environments (GOGREEN). This is an imaging and deep spectroscopic survey of 21 galaxy systems at 1 10 in halo mass. The scientific objectives include measuring the role of environment in the evolution of low-mass galaxies, and measuring the dynamics and stellar contents of their host haloes. The targets are selected from the SpARCS, SPT, COSMOS, and SXDS surveys, to be the evolutionary counterparts of today's clusters and groups. The new red-sensitive Hamamatsu detectors on GMOS, coupled with the nod-and-shuffle sky subtraction, allow simultaneous wavelength coverage over λ ∼ 0.6–1.05 μm, and this enables a homogeneous and statistically complete redshift survey of galaxies of all types. The spectroscopic sample targets galaxies with AB magnitudes z΄ < 24.25 and [3.6] μm < 22.5, and is therefore statistically complete for stellar masses M* ≳ 1010.3 M⊙, for all galaxy types and over the entire redshift range. Deep, multiwavelength imaging has been acquired over larger fields for most systems, spanning u through K, in addition to deep IRAC imaging at 3.6 μm. The spectroscopy is ∼50 per cent complete as of semester 17A, and we anticipate a final sample of ∼500 new cluster members. Combined with existing spectroscopy on the brighter galaxies from GCLASS, SPT, and other sources, GOGREEN will be a large legacy cluster and field galaxy sample at this redshift that spectroscopically covers a wide range in stellar mass, halo mass, and clustercentric radius