Recovering isolated galaxies from large scale surveys: problems and strategies

The large survey programs being performed nowadays, being the SDSS their flagship, provide us with morphological parameters which allow for extraction of large galaxy samples. We will analyze the methodology for obtaining an AMIGA-like catalogue of isolated galaxies from the SDSS DR5 photometric catalogue of galaxy objects, together with the roadblocks found in the process, and suggested workarounds.Comment: 4 pages, 2 figures, to appear in the Proceedings of the International Conference CIG09: Galaxies in Isolation, held in May 19th in Granada, Spai

Spectral Energy Distributions of a set of HII regions in M33 (HerM33es)

Within the framework of the HerM33es Key Project for Herschel and in combination with multi-wavelength data, we study the Spectral Energy Distribution (SED) of a set of HII regions in the Local Group Galaxy M33. Using the Halpha emission, we perform a classification of a selected HII region sample in terms of morphology, separating the objects in filled, mixed, shell and clear shell objects. We obtain the SED for each HII region as well as a representative SED for each class of objects. We also study the emission distribution of each band within the regions. We find different trends in the SEDs for each morphological type that are related to properties of the dust and their associated stellar cluster. The emission distribution of each band within the region is different for each morphological type of object.Comment: 3pages, 4 figures. To appear in 'The Spectral Energy Distribution of Galaxies' Proceedings IAU Symposium No 284, 201

SIT 45: An interacting, compact, and star-forming isolated galaxy triplet

Acknowledgements. We thank our referee whose valuable comments have certainly contributed to improve and clarify this paper. MAF and PVB acknowledge financial support by the DI-PUCV research project 039.481/2020. MAF also acknowledges support from FONDECYT iniciación project 11200107 and the Emergia program (EMERGIA20_38888) from Consejería de Transformación Económica, Industria, Conocimiento y Universidades and University of Granada. UL and DE acknowledge support from project PID2020-114414GB- 100, financed by MCIN/AEI/10.13039/501100011033. DE also acknowledges support from Beatriz Galindo senior fellowship (BG20/00224) financed by the Spanish Ministry of Science and Innovation, and project PID2020-114414GB- 100 financed by MCIN/AEI/10.13039/501100011033. UL, SV and DE acknowledge support from project P20_00334 financed by the Junta de Andalucía and from FEDER/Junta de Andalucía-Consejería de Transformación Económica, Industria, Conocimiento y Universidades/Proyecto A-FQM-510-UGR20. MB gratefully acknowledges support by the ANID BASAL project FB210003 and from the FONDECYT regular grant 1211000. SDP is grateful to the Fonds de Recherche du Québec – Nature et Technologies and acknowledges financial support from the Spanish Ministerio de Economía y Competitividad under grants AYA2016-79724-C4-4-P and PID2019-107408GB-C44, from Junta de Andalucía Excellence Project P18-FR-2664, and also acknowledges support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). This research made use of Astropy, a community-developed core Python (http://www.python.org) package for Astronomy (Astropy Collaboration 2013); Ipython (Pérez & Granger 2007); Matplotlib (Hunter 2007); Numpy (Walt et al. 2011); Scipy (Jones et al. 2001); and Topcat (Taylor 2005). This research made use of Astrodendro, a Python package to compute dendrograms of Astronomical data (http:// www.dendrograms.org/). This research has made use of the NASA/IPAC Extragalactic Database, operated by the Jet Propulsion Laboratory of the California Institute of Technology, un centract with the National Aeronautics and Space Administration. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy O ce of Science. The SDSS-III Web site is http://www.sdss3.org/. The SDSS-IV site is http://www.sdss. org. Based on observations made with the NASA Galaxy Evolution Explorer (GALEX). GALEX is operated for NASA by the California Institute of Technology under NASA contract NAS5-98034. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory /California Institute of Technology, funded by the National Aeronautics and Space Administration.Context. The underlying scenario of the formation and evolution of galaxy triplets is still uncertain. Mergers of galaxies in isolated triplets give us the opportunity to study the already complex merging process, with minimal contamination of other environmental effects that potentially allow and accelerate galaxy transitions from active star-forming to passive galaxies. Aims. The merging system SIT 45 (UGC 12589) is one of 315 systems in the SDSS-based catalogue of Isolated Triplets (SIT); it is an unusual isolated galaxy triplet, consisting of three merging late-type galaxies. The main aims of this work are to study the dynamical evolution and star formation history (SFH) of SIT 45, as well as its dependence on its local and large-scale environment. Methods. To study its dynamics, parameters such as the velocity dispersion (σv), the harmonic radius (RH), the crossing time (H0tc), and the virial mass (Mvir), along with the compactness of the triplet (S) were considered. To investigate the possible dependence of these dynamical parameters on the environment, the tidal force Q parameters (both local and large-scale) and the projected local density (ηk) were used. To constrain the SFH, we used CIGALE to fit its observed spectral energy distribution using multiwavelength data from the ultraviolet to the infrared. Results. SIT 45 is one of the most compact triplets in the SIT, and it is also more compact than triplets in other samples. According to its SFH, SIT 45 presents star formation, where the galaxies also present recent (∼200 Myr) star formation increase, indicating that this activity may have been triggered by the interaction. Its dynamical configuration suggests that the system is highly evolved in comparison to the SIT. However, this is not expected for systems composed of star-forming late-type galaxies, based on observations in compact groups. Conclusions. We conclude that SIT 45 is a system of three interacting galaxies that are evolving within the same dark matter halo; its compact configuration is a consequence of the ongoing interaction rather than being due to a long-term evolution (as suggested from its H0tc value). We consider two scenarios for the present configuration of the triplet, one where one of the members is a tidal galaxy, and another where this galaxy arrives to the system after the interaction. Both scenarios need further exploration. The isolated triplet SIT 45 is therefore an ideal system to study short timescale mechanisms (∼108 yr), such as starbursts triggered by interactions which are more frequent at higher redshift.DI-PUCV research project 039.481/2020FONDECYT iniciación project 11200107Emergia program (EMERGIA20_38888) from Consejería de Transformación Económica, Industria, Conocimiento y UniversidadesUniversity of GranadaProject PID2020-114414GB- 100, financed by MCIN/AEI/10.13039/501100011033Senior fellowship (BG20/00224) financed by the Spanish Ministry of Science and InnovationProject PID2020-114414GB- 100 financed by MCIN/AEI/10.13039/501100011033Project P20_00334 financed by the Junta de Andalucía and from FEDER/Junta de Andalucía-Consejería de Transformación Económica, Industria, Conocimiento y Universidades/Proyecto A-FQM-510-UGR20ANID BASAL project FB210003FONDECYT regular grant 1211000Fonds de Recherche du Québec – Nature et TechnologiesSpanish Ministerio de Economía y Competitividad under grants AYA2016-79724-C4-4-P and PID2019-107408GB-C44Junta de Andalucía Excellence Project P18-FR-2664State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709

Does the LFIR-LHCN correlation hold for low LFIR isolated galaxies?

International conference “Galaxies in Isolation: Exploring Nature vs. Nurture” held in Granada (Spain), May 12–15, 2009.Low LFIR Isolated Galaxies (IGs) from the AMIGA sample have low level of Star Formation (SF) activity. We observed the HCN(1-0) emission in a sample of IGs in order to test whether they follow the tight relation between LHCN and LFIR found for galaxies with more active SF

Metal production in M33: space and time variations

Nearby galaxies are ideal places to study in detail metallicity gradients and their time evolution. We consider chemical abundances of a new sample of \hii\ regions complemented with previous literature data-sets. We compare \hii\ region and PN abundances obtained with a common set of observations taken at MMT. With an updated theoretical model, we follow the time evolution of the baryonic components and chemical abundances in the disk of M33, assuming that the galaxy is accreting gas from an external reservoir. Supported by a uniform sample of nebular spectroscopic observations, we conclude that: {\em i}) the metallicity distribution in M33 is very complex, showing a central depression in metallicity probably due to observational bias; {\em ii}) the metallicity gradient in the disk of M33 has a slope of -0.037$\pm$ 0.009 dex kpc$^{-1}$ in the whole radial range up to $\sim$8 kpc, and -0.044$\pm$ 0.009 dex kpc$^{-1}$ excluding the central kpc; {\em iii}) there is a small evolution of the slope with time from the epoch of PN progenitor formation to the present-time.}Comment: A&A accepted, 15 Pags, 13 Figs, language correctio

Scaling relations of metallicity, stellar mass, and star formation rate in metal-poor starbursts: II. Theoretical models

Scaling relations of metallicity (O/H), star formation rate (SFR), and stellar mass give important insight on galaxy evolution. They are obeyed by most galaxies in the Local Universe and also at high redshift. In a companion paper, we compiled a sample of ~1100 galaxies from redshift 0 to ~3, spanning almost two orders of magnitude in metal abundance, a factor of $\sim10^6$ in SFR, and of ~10^5 in stellar mass. We have characterized empirically the star-formation "main sequence" (SFMS) and the mass-metallicity relation (MZR) for this sample, and also identified a class of low-metallicity starbursts, rare locally but more common in the distant universe. These galaxies deviate significantly from the main scaling relations, with high SFR and low metal content for a given M*. In this paper, we model the scaling relations and explain these deviations from them with a set of multi-phase chemical evolution models based on the idea that, independently of redshift, initial physical conditions in a galaxy's evolutionary history can dictate its location in the scaling relations. Our models are able to successfully reproduce the O/H, M*, and SFR scaling relations up to z~3, and also successfully predict the molecular cloud fraction as a function of stellar mass. These results suggest that the scaling relations are defined by different modes of star formation: an "active" starburst mode, more common at high redshift, and a quiescent "passive" mode that is predominant locally and governs the main trends.Comment: 17 pages, 7 figures, accepted for publication by MNRA

Molecular Gas and Star Formation Properties in Early Stage Mergers:SMA CO(2-1) Observations of the LIRGs NGC 3110 and NGC 232

Mergers of galaxies are an important mode for galaxy evolution because they serve as an efficient trigger of powerful starbursts. However, observational studies of the molecular gas properties during their early stages are scarce. We present interferometric CO(2-1) maps of two luminous infrared galaxies (LIRGs), NGC 3110 and NGC 232, obtained with the Submillimeter Array (SMA) with ~ 1 kpc resolution. While NGC 3110 is a spiral galaxy interacting with a minor (14:1 stellar mass) companion, NGC 232 is interacting with a similarly sized object. We find that such interactions have likely induced in these galaxies enhancements in the molecular gas content and central concentrations, partly at the expense of atomic gas. The obtained molecular gas surface densities in their circumnuclear regions are $\Sigma_{\rm mol}~\gtrsim10^{2.5}$ M$_\odot$ pc$^{-2}$, higher than in non-interacting objects by an order of magnitude. Gas depletion times of ~ 0.5 - 1 Gyr are found for the different regions, lying in between non-interacting disk galaxies and the starburst sequence. In the case of NGC 3110, the spiral arms show on average 0.5 dex shorter depletion times than in the circumnuclear regions if we assume a similar H$_2$-CO conversion factor. We show that even in the early stages of the interaction with a minor companion, a starburst is formed along the circumnuclear region and spiral arms, where a large population of SSCs is found (~350), and at the same time a large central gas concentration is building up which might be the fuel for an active galactic nucleus. The main morphological properties of the NGC 3110 system are reproduced by our numerical simulations and allow us to estimate that the current epoch of the interaction is at ~ 150 Myrs after closest approach.Comment: 30 pages. Accepted for publication in Ap

Global ensemble projections reveal trophic amplification of ocean biomass declines with climate change

While the physical dimensions of climate change are now routinely assessed through multimodel intercomparisons, projected impacts on the global ocean ecosystem generally rely on individual models with a specific set of assumptions. To address these single-model limitations, we present standardized ensemble projections from six global marine ecosystem models forced with two Earth system models and four emission scenarios with and without fishing. We derive average biomass trends and associated uncertainties across the marine food web. Without fishing, mean global animal biomass decreased by 5% (±4% SD) under low emissions and 17% (±11% SD) under high emissions by 2100, with an average 5% decline for every 1 °C of warming. Projected biomass declines were primarily driven by increasing temperature and decreasing primary production, and were more pronounced at higher trophic levels, a process known as trophic amplification. Fishing did not substantially alter the effects of climate change. Considerable regional variation featured strong biomass increases at high latitudes and decreases at middle to low latitudes, with good model agreement on the direction of change but variable magnitude. Uncertainties due to variations in marine ecosystem and Earth system models were similar. Ensemble projections performed well compared with empirical data, emphasizing the benefits of multimodel inference to project future outcomes. Our results indicate that global ocean animal biomass consistently declines with climate change, and that these impacts are amplified at higher trophic levels. Next steps for model development include dynamic scenarios of fishing, cumulative human impacts, and the effects of management measures on future ocean biomass trends

“Far-field” torque evaluation of a helicopter rotor in hover : Analysis on results of numerical simulations of fluid mechanics

Dans cette thèse, une formulation pour l’extraction du couple « champ lointain » d’un rotor d’hélicoptère en vol stationnaire est présentée. Cette formulation est dérivée de la méthode d’extraction de la traînée « champ lointain » d’un avion, basée sur les travaux de van der Vooren et Destarac [?, ?, ?]. Un outil développé à l’Onera à partir de cette théorie permet de donner une analyse complète de la traînée aérodynamique d’un avion. Il est basé sur l’analyse physique et locale de l’écoulement calculé autour de l’aéronef, et décompose la traînée totale, aussi appelée traînée mécanique, en composantes physiques. Ces composantes physiques peuvent être définies comme suit : 1) la traînée d’onde, 2) la traînée visqueuse, 3) la traînée induite. L’adaptation de la méthode d’extraction de la traînée d’un avion à un rotor en vol stationnaire nécessite l’utilisation du couple rotor à la place de la traînée de l’avion, ce qui donne la décomposition suivante : 1) le couple d’onde, 2) le couple visqueux, 3) le couple induit. Les simulations de rotor diffèrent de celles de l’avion dans la mesure où les équations d’Euler (ou RANS) ne sont pas écrites dans le même repère de référence : les simulations d’avion utilisent généralement une formulation en vitesse relative tandis que les simulations d’un rotor d’hélicoptère utilisent la vitesse absolue projetée dans le repère relatif. Cette différence conduit à deux formulations différentes des équations de l’écoulement, et nécessairement deux formulations différentes de l’extraction de la traînée ou du couple. Ce changement de repère implique aussi des changements dans les quantités thermodynamiques utilisées, en particulier l’utilisation de la rothalpie à la place de l’enthalpie d’arrêt pour déterminer le couple dû aux phénomènes irréversibles. Une application de cette méthode est présentée sur un rotor quadripale créé pour cette étude et montre comment cette nouvelle approche peut améliorer la précision de l’extraction des performances d’un rotor à partir de résultat issu de la simulation numérique.In this thesis, a formulation for “far-field” torque extraction in the case of a hovering rotor is presented. This formulation is derived from an aircraft “far-field” drag extraction method, based on van der Vooren and Destarac’s works [?, ?, ?]. A tool was previously developed at Onera to give an aerodynamic comprehensive analysis of aircraft drag, based on physical and local analysis of the computed flow field surrounding the aircraft. It decomposes the total drag, also called mechanical drag, into its physical components. These physical components can be defined as : 1) wave drag, 2) viscous drag, 3) induced drag. The adaptation of the method to a rotor in hover leads to consider rotor torque instead of aircraft drag, which gives the following decomposition : 1) wave torque, 2) viscous torque, 3) induced torque. Rotor simulations differ from aircraft ones inasmuch as the Euler (or RANS) equations are not written in the same reference frame : aircraft simulations use the relative velocity formulation while rotor simulations use the absolute velocity projected in the relative frame. This difference leads to two different formulations of the flow equations, and necessarily two different formulations of the drag or torque extraction. This change of reference frame also implies some changes in the thermodynamical quantities used, in particular the use of the rothalpy instead of the stagnation enthalpy to determine the torque due to irreversible phenomena. An application of this method is described on a four-bladed rotor created for this study and shows how this method can improve rotor performance extraction from numerical simulations