Local metallicity in simulated galaxies

En la ultima década, la espectroscopia de campo integrado ha expandido nuestra comprensión de la evolución química de las galaxias, dando evidencia de un gradiente radial de la metalicidad de la fase gaseosa. En este trabajo, usamos la simulación cosmologica hidrodinamica eagle para estudiar las propiedades localmente resueltas de las galaxias. Mostramos que la metalicidad local del gas correlaciona con la densidad superficial de masa estelar y anticorrelaciona con la acrecion de gas. Los perfiles de metalicidad resueltos actúan como buenos estimadores de la acrecion de gas, y pueden ser usados para entender los cambios en el enriquecimiento químico de las galaxiasIn the last decade, integral field spectroscopy has expanded our understanding of chemical evolution of galaxies, giving evidence of a radial gradient of gas-phase metallicity. In this work, we use the state-of-art hydrodynamical simulation EAGLE to study the resolved, local properties of galaxies. We show that the local gas metallicity correlates with the stellar mass surface density and anti-correlates with the gas accretion. Resolved metallicity profiles acts as a good estimator of gas accretion, and can be used to understand the changes in the chemical enrichment of galaxies.Fil: Collacchioni, Florencia. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Correa, C. A.. University of Western Australia; AustraliaFil: Lagos, C .D. P.. Universidad de Copenhagen; DinamarcaFil: Cora, Sofia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina62° Reunión Anual de la Asociación Argentina de AstronomíaRosarioArgentinaAsociación Argentina de Astronomí

How much dark matter is there inside early-type galaxies?

We study the luminous mass as a function of the dynamical mass inside the effective radius (r_e) of early-type galaxies (ETGs) to search for differences between these masses. We assume Newtonian dynamics and that any difference between these masses is due to the presence of dark matter. We use several samples of ETGs -ranging from 19 000 to 98 000 objects- from the ninth data release of the Sloan Digital Sky Survey. We perform Monte Carlo (MC) simulations of galaxy samples and compare them with real samples. The main results are: i) MC simulations show that the distribution of the dynamical vs. luminous mass depends on the mass range where the ETGs are distributed (geometric effect). This dependence is caused by selection effects and intrinsic properties of the ETGs. ii) The amount of dark matter inside r_e is approximately 7% +- 22%. iii) This amount of dark matter is lower than the minimum estimate (10%) found in the literature and four times lower than the average (30%) of literature estimates. However, if we consider the associated error, our estimate is of the order of the literature average.Comment: 24 pages, 12 figures. MNRAS accepte

Halo merger tree comparison: impact on galaxy formation models

We examine the effect of using different halo finders and merger tree building algorithms on galaxy properties predicted using the GALFORM semi-analytical model run on a high resolution, large volume dark matter simulation. The halo finders/tree builders HBT, ROCKSTAR, SUBFIND, and VELOCI RAPTOR differ in their definitions of halo mass, on whether only spatial or phase-space information is used, and in how they distinguish satellite and main haloes; all of these features have some impact on the model galaxies, even after the trees are post-processed and homogenized by GALFORM. The stellar mass function is insensitive to the halo and merger tree finder adopted. However, we find that the number of central and satellite galaxies in GALFORM does depend slightly on the halo finder/tree builder. The number of galaxies without resolved subhaloes depends strongly on the tree builder, with VELOCIRAPTOR, a phase-space finder, showing the largest population of such galaxies. The distributions of stellar masses, cold and hot gas masses, and star formation rates agree well between different halo finders/tree builders. However, because VELOCIRAPTOR has more early progenitor haloes, with these trees GALFORM produces slightly higher star formation rate densities at high redshift, smaller galaxy sizes, and larger stellar masses for the spheroid component. Since in all cases these differences are small we conclude that, when all of the trees are processed so that the main progenitor mass increases monotonically, the predicted GALFORM galaxy populations are stable and consistent for these four halo finders/tree builders

SMM J04135+10277: a distant QSO-starburst system caught by ALMA

The gas content of galaxies is a key factor for their growth, starting from star formation and black hole accretion to galaxy mergers. Thus, characterizing its properties through observations of tracers like the CO emission line is of big importance in order to understand the bigger picture of galaxy evolution. We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of dust continuum, CO(5-4) and CO(8-7) line emission in the quasar-star-forming companion system SMM J04135+10277 (z = 2.84). Earlier low-J CO studies of this system found a huge molecular gas reservoir associated with the companion galaxy, while the quasar appeared gas-poor. Our CO observations revealed that the host galaxy of the quasar is also gas-rich, with an estimated molecular gas mass of ∼ (0.7-2.3) 7 10^{10} M_{☉}. The CO line profiles of the companion galaxy are very broad (∼ 1000 km s^{-1}), and show signs of rotation of a compact, massive system. In contrast to previous far-infrared observations, we resolve the continuum emission and detect both sources, with the companion galaxy dominating the dust continuum and the quasar having a ∼ 25{{ per cent}} contribution to the total dust emission. By fitting the infrared spectral energy distribution of the sources with MR-MOOSE and empirical templates, the infrared luminosities of the quasar and the companion are in the range of L_{IR, QSO}∼ (2.1-9.6) 7 10^{12} L_{☉} and L_{IR, Comp.}∼ (2.4-24) 7 10^{12} L_{☉}, while the estimated star formation rates are ∼ 210-960 and ∼ 240-2400 M_{☉} yr^{-1}, respectively. Our results demonstrate that non-detection of low-J CO transition lines in similar sources does not necessarily imply the absence of massive molecular gas reservoir but that the excitation conditions favour the excitation of high-J transitions