53 research outputs found
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 iniciaciĂłn project 11200107 and
the Emergia program (EMERGIA20_38888) from ConsejerĂa de TransformaciĂłn
EconĂłmica, 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 AndalucĂa and
from FEDER/Junta de AndalucĂa-ConsejerĂa de TransformaciĂłn EconĂłmica,
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 QuĂ©bec â Nature et Technologies and acknowledges
financial support from the Spanish Ministerio de EconomĂa y Competitividad
under grants AYA2016-79724-C4-4-P and PID2019-107408GB-C44, from
Junta de AndalucĂa Excellence Project P18-FR-2664, and also acknowledges support from the State Agency for Research of the Spanish MCIU through
the âCenter of Excellence Severo Ochoaâ award for the Instituto de AstrofĂsica
de AndalucĂa (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 (PĂ©rez & 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 (Ïv), 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 (âŒ200 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 (âŒ108 yr), such as starbursts triggered by interactions which are more frequent at higher redshift.DI-PUCV research project 039.481/2020FONDECYT iniciaciĂłn project 11200107Emergia program (EMERGIA20_38888) from ConsejerĂa de TransformaciĂłn EconĂłmica, 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 AndalucĂa and from FEDER/Junta de AndalucĂa-ConsejerĂa de TransformaciĂłn EconĂłmica, Industria, Conocimiento y Universidades/Proyecto A-FQM-510-UGR20ANID BASAL project FB210003FONDECYT regular grant 1211000Fonds de Recherche du QuĂ©bec â Nature et TechnologiesSpanish Ministerio de EconomĂa y Competitividad under grants AYA2016-79724-C4-4-P and PID2019-107408GB-C44Junta de AndalucĂa Excellence Project P18-FR-2664State Agency for Research of the Spanish MCIU through the âCenter of Excellence Severo Ochoaâ award for the Instituto de AstrofĂsica de AndalucĂa (SEV-2017-0709
Does the LFIR-LHCN correlation hold for low LFIR isolated galaxies?
International conference âGalaxies in Isolation: Exploring Nature vs. Nurtureâ held in Granada (Spain), May 12â15, 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 0.009 dex kpc in
the whole radial range up to 8 kpc, and -0.044 0.009 dex kpc
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 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 M
pc, 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-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
âFar-fieldâ torque evaluation of a helicopter rotor in hover : Analysis on results of numerical simulations of fluid mechanics
Dans cette thĂšse, une formulation pour lâextraction du couple « champ lointain » dâun rotor dâhĂ©licoptĂšre en vol stationnaire est prĂ©sentĂ©e. Cette formulation est dĂ©rivĂ©e de la mĂ©thode dâextraction de la traĂźnĂ©e « champ lointain » dâun avion, basĂ©e sur les travaux de van der Vooren et Destarac [?, ?, ?]. Un outil dĂ©veloppĂ© Ă lâOnera Ă partir de cette thĂ©orie permet de donner une analyse complĂšte de la traĂźnĂ©e aĂ©rodynamique dâun avion. Il est basĂ© sur lâanalyse physique et locale de lâĂ©coulement calculĂ© autour de lâaĂ©ronef, et dĂ©compose la traĂźnĂ©e totale, aussi appelĂ©e traĂźnĂ©e mĂ©canique, en composantes physiques. Ces composantes physiques peuvent ĂȘtre dĂ©finies comme suit : 1) la traĂźnĂ©e dâonde, 2) la traĂźnĂ©e visqueuse, 3) la traĂźnĂ©e induite. Lâadaptation de la mĂ©thode dâextraction de la traĂźnĂ©e dâun avion Ă un rotor en vol stationnaire nĂ©cessite lâutilisation du couple rotor Ă la place de la traĂźnĂ©e de lâavion, ce qui donne la dĂ©composition suivante : 1) le couple dâonde, 2) le couple visqueux, 3) le couple induit. Les simulations de rotor diffĂšrent de celles de lâavion dans la mesure oĂč les Ă©quations dâEuler (ou RANS) ne sont pas Ă©crites dans le mĂȘme repĂšre de rĂ©fĂ©rence : les simulations dâavion utilisent gĂ©nĂ©ralement une formulation en vitesse relative tandis que les simulations dâun rotor dâhĂ©licoptĂšre utilisent la vitesse absolue projetĂ©e dans le repĂšre relatif. Cette diffĂ©rence conduit Ă deux formulations diffĂ©rentes des Ă©quations de lâĂ©coulement, et nĂ©cessairement deux formulations diffĂ©rentes de lâextraction de la traĂźnĂ©e ou du couple. Ce changement de repĂšre implique aussi des changements dans les quantitĂ©s thermodynamiques utilisĂ©es, en particulier lâutilisation de la rothalpie Ă la place de lâenthalpie dâarrĂȘt pour dĂ©terminer le couple dĂ» aux phĂ©nomĂšnes irrĂ©versibles. Une application de cette mĂ©thode est prĂ©sentĂ©e sur un rotor quadripale crĂ©Ă© pour cette Ă©tude et montre comment cette nouvelle approche peut amĂ©liorer la prĂ©cision de lâextraction des performances dâun rotor Ă partir de rĂ©sultat issu de la simulation numĂ©rique.In this thesis, a formulation for âfar-fieldâ torque extraction in the case of a hovering rotor is presented. This formulation is derived from an aircraft âfar-fieldâ drag extraction method, based on van der Vooren and Destaracâs 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
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