Combining friend-of-friend and halo-based algorithms for the identification of galaxy groups

Galaxy groups provide the means for a great diversity of studies that contribute to a better understanding of the structure ofthe universe on a large scale and allow the properties of galaxies to be linked to those of the host halos. However, the identification ofgalaxy systems is a challenging task and therefore it is necessary to improve the techniques involved as much as possible.Aims. In view of the large present and forthcoming galaxy catalogues, we propose, implement, and evaluate an algorithm that combines the two most popular techniques used to identify galaxy systems. The algorithm can be easily applied to any spectroscopicgalaxy catalogue, but here we demonstrate its use on the Sloan Digital Sky Survey.Methods. Assuming that a galaxy group is a gravitationally bounded system that has at least one bright galaxy, we begin by identifying groups with a friends-of-friends algorithm adapted to fit this definition. In view of the shortcomings of this method, particularlythe lack of ability to identify low-number groups, and consequently the inability to study the occupation of halos throughout the massrange, we improve it by adding a halo-based procedure. To assess the performance, we construct a mock catalogue from a semianalytical model to compare the groups identified using our method with those obtained from the simulation.Results. The comparison of groups extracted using our method with those of a mock catalogue shows that the proposed algorithmprovides excellent results. The modifications introduced to the friends-of-friends algorithm in the first part of the procedure to fit theadopted group definition gave reliable groups. Furthermore, incorporation of the halo-based method reduces the interlopers whilemore accurately reproducing the number of galaxies per group. As a specific application, we use the algorithm to extract groups fromthe Sloan Digital Sky SurveyFil: Rodriguez, Facundo. 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: Merchan, Manuel Enrique. 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

Deviations from tidal torque theory: Environment dependences on halo angular momentum growth

The tidal torque theory (TTT) relates the origin and evolution of angular momentum with the environment in which dark matter (DM) haloes form. The deviations introduced by late non-linearities are commonly thought as noise in the model. In this work, we analyse a cosmological simulation looking for systematics on these deviations, finding that the classification of DM haloes according to their angular momentum growth results in samples with different internal alignment, spin parameter distribution, and assembly history. Based on this classification, we obtain that low-mass haloes are embedded in denser environments if they have acquired angular momentum below the TTT expectations (L haloes), whereas at high masses enhanced clustering is typically associated with higher angular momentum growths (W haloes). Additionally, we find that the low-mass signal has a weak dependence on the direction, whereas the high-mass signal is entirely due to the structure perpendicular to the angular momentum. Finally, we study the anisotropy of the matter distribution around haloes as a function of their mass. We find that the angular momentum direction of W (L) haloes remains statistically perpendicular (parallel) to the surrounding structure across the mass range 11 < log(M/h-1M⊙) < 14, whereas haloes following TTT show a 'spin flip' mass consistent with previously reported values (∼5 × 1012 h-1M⊙). Hence, whether the spin flip mass of the deviated samples is highly shifted or straightly undefined, our results indicate that it is remarkably connected to the haloes angular momentum growth.Fil: López, Pablo. 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: Merchan, Manuel Enrique. 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: Paz, Dante Javier. 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

Taking advantage of photometric galaxy catalogues to determine the halo occupation distribution

Context. Halo occupation distribution (HOD) is a powerful statistic that allows the study of several aspects of the matter distribution in the Universe, such as evaluating semi-analytic models of galaxy formation or imposing constraints on cosmological models. Consequently, it is important to have a reliable method for estimating this statistic, taking full advantage of the available information on current and future galaxy surveys. Aims. The main goal of this project is to combine photometric and spectroscopic information using a discount method of background galaxies in order to extend the range of absolute magnitudes and to increase the upper limit of masses in which the HOD is estimated. We also evaluate the proposed method and apply it to estimating the HOD on the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) galaxy survey. Methods. We propose the background subtraction technique to mel information provided by spectroscopic galaxy groups and photometric survey of galaxies. To evaluate the feasibility of the method, we implement the proposed technique on a mock catalogue built from a semi-analytic model of galaxy formation. Furthermore, we apply the method to the SDSS DR7 using a galaxy group catalogue taken from spectroscopic version and the corresponding photometric galaxy survey. Results. We demonstrated the validity of the method using the mock catalogue. We applied this technique to obtain the SDSS DR7 HOD in absolute magnitudes ranging from M = -21.5 to M = -16.0 and masses up to 1015 M⊙ throughout this range. On the brighter extreme, we found that our results are in excellent agreement with those obtained in previous works.Fil: Rodriguez, Facundo. 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: Merchan, Manuel Enrique. 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: Sgró, Mario Agustín. 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 MeSsI (merging systems identification) algorithm and catalogue

Merging galaxy systems provide observational evidence of the existence of dark matter and constraints on its properties. Therefore, statistically uniform samples of merging systems would be a powerful tool for several studies. In this paper, we present a new methodology for the identification of merging systems and the results of its application to galaxy redshift surveys.We use as a starting point amock catalogue of galaxy systems, identified using friendsof- friends algorithms, that have experienced a major merger, as indicated by its merger tree. By applying machine learning techniques in this training sample, and using several features computed from the observable properties of galaxy members, it is possible to select galaxy groups that have a high probability of having experienced a major merger. Next, we apply a mixture of Gaussian techniques on galaxy members in order to reconstruct the properties of the haloes involved in such mergers. This methodology provides a highly reliable sample of merging systems with low contamination and precisely recovered properties. We apply our techniques to samples of galaxy systems obtained from the Sloan Digital Sky Survey Data Release 7, theWide-Field Nearby Galaxy-Cluster Survey (WINGS) and the Hectospec Cluster Survey (HeCS). Our results recover previously known merging systems and provide several new candidates. We present their measured properties and discuss future analysis on current and forthcoming samples.Fil: De Los Rios, Martín. 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, Mariano. 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: Paz, Dante Javier. 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: Merchan, Manuel Enrique. 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

Effects of environment on sSFR profiles of late-type galaxies in the CALIFA survey

We explore the effects of environment on star formation in late-type galaxies by studying the dependence of the radial profiles of specific star formation rate (sSFR) on environment and the stellar mass, using a sample of 275 late-type galaxies drawn from the CALIFA survey. We consider three different discrete environments: Field galaxies, galaxies in pairs, and galaxies in groups, with stellar masses 9 ≤ log(M∗=M⊙) ≤ 12, and compare their sSFR profiles across the environments. Results. Our results suggest that the stellar mass is the main factor determining the sSFR profiles of late-type galaxies; the influence of AGNs and bars are secondary. We find that the relative size of the bulge plays a key role in depressing star formation towards the center of late-type galaxies. The group environment determines clear differences in the sSFR profiles of galaxies.We find evidence of an outside-in action upon galaxies with stellar masses 9 ≤ log(M∗=M⊙) ≤ 10 in groups. We find a much stronger suppression of star formation in the inner regions of massive galaxies in groups, which may be an indication of a different merger history.Fil: Coenda, Valeria. Observatorio Astronomico de la Universidad Nacional de Cordoba; 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: Mast, Damian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Observatorio Astronomico de la Universidad Nacional de Cordoba; ArgentinaFil: Martinez Atencio, Hector Julian. 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. Observatorio Astronomico de la Universidad Nacional de Cordoba; ArgentinaFil: Muriel, Hernan. Observatorio Astronomico de la Universidad Nacional de Cordoba; 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: Merchan, Manuel Enrique. 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. Observatorio Astronomico de la Universidad Nacional de Cordoba; Argentin

On the weak lensing masses of a new sample of galaxy groups

Galaxy group masses are important to relate these systems with the dark matter halo hosts. However, deriving accurate mass estimates is particularly challenging for low-mass galaxy groups. Moreover, calibration of observational mass-proxies using weak-lensing estimates have been mainly focused on massive clusters. We present here a study of halo masses for a sample of galaxy groups identified according to a spectroscopic catalogue, spanning a wide mass range. The main motivation of our analysis is to assess mass estimates provided by the galaxy group catalogue derived through an abundance matching luminosity technique. We derive total halo mass estimates according to a stacking weak-lensing analysis. Our study allows to test the accuracy of mass estimates based on this technique as a proxy for the halo masses of large group samples. Lensing profiles are computed combining the groups in different bins of abundance matching mass, richness, and redshift. Fitted lensing masses correlate with the masses obtained from abundance matching. However, when considering groups in the low-and intermediate-mass ranges, masses computed according to the characteristic group luminosity tend to predict higher values than the determined by the weak-lensing analysis. The agreement improves for the low-mass range if the groups selected have a central early-Type galaxy. Presented results validate the use of mass estimates based on abundance matching techniques, which provide good proxies to the halo host mass in a wide mass range.Fil: Gonzalez, Elizabeth Johana. 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. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Rodriguez, Facundo. 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: Merchan, Manuel Enrique. 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: Garcia Lambas, Diego Rodolfo. 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: Makler, Martín. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología. Centro Internacional de Estudios Avanzados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias Físicas. - Universidad Nacional de San Martín. Instituto de Ciencias Físicas; Argentina. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Chalela, Martín. 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: Pereira, Maria E. S.. University of Michigan. Department of Physics; Estados UnidosFil: Moraes, Bruno. Universidade Federal do Rio de Janeiro; BrasilFil: Shan, HuanYuan. Chinese Academy of Sciences; República de China. Shanghai Astronomical Observatory; Chin

Subhaloes gone Notts: subhaloes as tracers of the dark matter halo shape

We study the shapes of subhalo distributions from four dark-matter-only simulations of Milky Way-type haloes. Comparing the shapes derived from the subhalo distributions at high resolution to those of the underlying dark matter fields, we find the former to be more triaxial if the analysis is restricted to massive subhaloes. For three of the four analysed haloes, the increased triaxiality of the distributions of massive subhaloes can be explained by a systematic effect caused by the low number of objects. Subhaloes of the fourth halo show indications for anisotropic accretion via their strong triaxial distribution and orbit alignment with respect to the dark matter field. These results are independent of the employed subhalo finder. Comparing the shape of the observed Milky Way satellite distribution to those of high-resolution subhalo samples from simulations, we find agreement for samples of bright satellites, but significant deviations if faint satellites are included in the analysis. These deviations might result from observational incompleteness

Catálogo de Grupos de Galaxias del SDSS DR12

Se presentan dos catálogos de grupos identificados en el SDSS DR12 y sus respectivos catálogos de galaxias. Para la construcción de estos catálogos se definió a los grupos como sistemas de las galaxias ligados gravitacionalmente con al menos una galaxia brillante (magnitud absoluta < -19.5 en la banda r ). En los catálogos FOF_mod se presentan los datos correspondientes a los grupos obtenidos mediante una identificación FOF (Friend-of-friends) en la cual se tuvo en cuenta la definición de grupos antes mencionada. En los catálogos FINAL se listan las galaxias y grupos de galaxias resultantes del proceso completo de combinar el método FOF con un algoritmo basado en halos. Ambos catálogos de grupos contienen información de los grupos obtenida dinámicamente y realizando un método de coincidencia de abundancia con la luminosidad. Los detalles de cómo se realizan estos cálculos se presentan en la publicación correspondiente.Fil: Rodriguez, Facundo. 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: Merchan, Manuel Enrique. 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

Galaxy groups in the third data release of the sloan digital sky survey

We present a new sample of galaxy groups identified in the Sloan Digital Sky Survey Data Release 3. Following previous works, we use the well-tested friends-of-friends algorithm developed by Huchra and Geller, which takes into account the number density variation due to the apparent magnitude limit of the galaxy catalog. To improve the identification, we implement a procedure to avoid the artificial merging of small systems in high-density regions and then apply an iterative method to recompute the group centers position. As a result, we obtain a new catalog with 10,864 galaxy groups with at least four members. The final group sample has a mean redshift of 0.1 and a median velocity dispersion of 230 km s-1.Fil: Merchan, Manuel Enrique. 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: Zandivarez, Arnaldo Ariel. 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

Alignment of the central galaxies with the environment

In this work, we combine ellipticity and major axis position angle measurements from the Sloan Digital Sky Server Data Release 16 with the group finder algorithm of Rodriguez & Merchan to determine the alignment of the central galaxies with the surrounding structures and satellite galaxies lying in their group. We use two independent methods: a modified version of the two- point cross-correlation function and the angle between the central galaxy orientation and the satellite galaxies relative position. The first method allows us to study the inner and outer regions of the cluster, while the second method provides information within the haloes. Our results show that central galaxies present anisotropy in the correlation function up to ∼10 h -1 Mpc , which becomes ∼10 per cent stronger for the brightest ones ( 0.1 M r < -21.5). When we split the galaxy sample by colour, we find that red central galaxies are the main contributors to this anisotropy. We also show that this behaviour does not depend on the group mass or central galaxy ellipticity . Finally , our results are in agreement with previous findings, showing that the two-point cross-correlation function is a good tracer of the galaxy alignments using all galaxies and not only those of the group to which it belongs. In addition, this feature allows us to explore the behaviour of the alignment on larger scales.Fil: Rodriguez, Facundo. 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: Merchan, Manuel Enrique. 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: Artale, Maria Celeste. 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. Università di Padova; Italia. Istituto Nazionale di Fisica Nucleare; Itali