Gamma ray bursts (GRBs) belong to the most energetic events in the Universe.
Recently, the extragalactic nature of these sources has been confirmed with the
discovery of several host galaxies (HGs) and the measurement of their
redshifts. To explain the origin of GRBs various models have been proposed,
among which the coalescence of compact objects and the "collapsar" scenarios
are the most representative, being the collapsar model one of the most accepted
to explain the long duration GRBs. A natural consequence of this model is that
the GRBs would trace the star formation rate (SFR) of their HGs. In this
contributed paper we present preliminary results of the development of a
Montecarlo-based code for collapsar event formation which is coupled to
chemical-cosmological simulations aiming at studying the properties of HGs in a
hierarchical scenario.Comment: Minor changes after referee report. To appear in the 48th Bulletin of
  the Argentine Astronomical Society (BAAA 48, 2005). 4 pages, baaa-eng.st

De Rossi, M. E.

Lambas, D. G.

Nuza, S. E.

Pellizza, L. J.

Scannapieco, C.

Tissera, P. B.

English

arXiv

Gamma ray bursts (GRBs) belong to the most energetic events in the Universe. Recently, the extragalactic nature of these sources has been confirmed with the discovery of several host galaxies (HGs) and the measurement of their redshifts. To explain the origin of GRBs various models have been proposed, among which the coalescence of compact objects and the collapsar scenarios are the most representative, being the collapsar model one of the most accepted to explain the long duration GRBs. A natural consequence of this model is that the GRBs would
trace the star formation rate (SFR) of their HGs. In this contributed paper we present preliminary results of the development of a Montecarlobased code for collapsar event formation which is coupled to chemical-cosmological simulations aiming at studying the properties of HGs in a hierarchical scenario.Las explosiones de radiacion gamma (ERG) se encuentran entre los eventos mas energeticos del Universo. Recientemente, la naturaleza extragalactica de estas fuentes fue confirmada con el descubrimiento de varias de sus galaxias huesped y la medicion de sus corrimientos al rojo. Para explicar su origen, varios modelos han sido propuestos, entre los cuales las colisiones de objetos compactos en sistemas binarios y los llamados collapsars son los mas representativos, siendo este ultimo ´ modelo uno de los mas aceptados para explicar las ERG de larga duracion. Una consecuencia natural del mismo es que las ERG trazarıan la tasa de formacion estelar de sus respectivas galaxias. En esta comunicacion se presentan resultados preliminares del desarrollo de un codigo Montecarlo para la formacion de collapsars en simulaciones quımico-cosmologicas, con el fin de estudiar las propiedades de sus galaxias huesped en un escenario
jer´arquico.Fil: Nuza, Sebastian Ernesto. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Tissera, Patricia Beatriz. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Pellizza González, Leonardo Javier. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina. Commissariat A Energie Atomique; FranciaFil: Garcia Lambas, Diego Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomia Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomia Teórica y Experimental; ArgentinaFil: Scannapieco, Cecilia. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: de Rossi, Maria Emilia. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Nuza, Sebastian Ernesto

Tissera, Patricia Beatriz

Pellizza González, Leonardo Javier

Garcia Lambas, Diego Rodolfo

Scannapieco, Cecilia

de Rossi, Maria Emilia

CONICET Digital

Asociacio´n Argentina de Astronomı´aBAAA, Vol. 48, 2005E.M. Arnal, A. Brunini, J.J. Claria´ Olmedo, J.C. Forte, D.O. Go´mez, D. Garc´ıa Lambas,Z. Lo´pez Garc´ıa, S. M. Malaroda, & G.E. Romero, eds.COMUNICACIO´N DE TRABAJO – CONTRIBUTED PAPERStudy of the relationship between the gamma ray burstsand their host galaxiesSebastia´n E. NuzaInstituto de Astronomı´a y F´ısica del Espacio, Buenos Aires, Argentina;sebasn@iafe.uba.arPatricia B. TisseraInstituto de Astronomı´a y F´ısica del Espacio, Buenos Aires, Argentina;patricia@iafe.uba.arLeonardo J. PellizzaService d’Astrophysique, DSM/DAPNIA, CEA, Saclay, France;leonardo.pellizza@cea.frDiego Garc´ıa LambasIATE, Observatorio Astrono´mico de Co´rdoba, Co´rdoba, Argentina;dgl@oac.uncor.eduCecilia ScannapiecoInstituto de Astronomı´a y F´ısica del Espacio, Buenos Aires, Argentina;cecilia@iafe.uba.arMar´ıa E. De RossiInstituto de Astronomı´a y F´ısica del Espacio, Buenos Aires, Argentina;derossi@iafe.uba.arAbstract. Gamma ray bursts (GRBs) belong to the most energeticevents in the Universe. Recently, the extragalactic nature of these sourceshas been confirmed with the discovery of several host galaxies (HGs) andthe measurement of their redshifts. To explain the origin of GRBs variousmodels have been proposed, among which the coalescence of compactobjects and the collapsar scenarios are the most representative, being thecollapsar model one of the most accepted to explain the long durationGRBs. A natural consequence of this model is that the GRBs wouldtrace the star formation rate (SFR) of their HGs. In this contributedpaper we present preliminary results of the development of a Montecarlo-based code for collapsar event formation which is coupled to chemical-459460 S. E. Nuza et al.cosmological simulations aiming at studying the properties of HGs in ahierarchical scenario.Resumen. Las explosiones de radiacio´n gamma (ERG) se encuentranentre los eventos ma´s energe´ticos del Universo. Recientemente, la natu-raleza extragala´ctica de estas fuentes fue confirmada con el descubrim-iento de varias de sus galaxias hue´sped y la medicio´n de sus corrimientosal rojo. Para explicar su origen, varios modelos han sido propuestos, entrelos cuales las colisiones de objetos compactos en sistemas binarios y losllamados collapsars son los ma´s representativos, siendo este u´ltimo mod-elo uno de los ma´s aceptados para explicar las ERG de larga duracio´n.Una consecuencia natural del mismo es que las ERG trazar´ıan la tasa deformacio´n estelar de sus respectivas galaxias. En esta comunicacio´n sepresentan resultados preliminares del desarrollo de un co´digo Montecarlopara la formacio´n de collapsars en simulaciones qu´ımico-cosmolo´gicas, conel fin de estudiar las propiedades de sus galaxias hue´sped en un escenariojera´rquico.1. IntroductionThe gamma ray bursts (GRBs) are the most energetic electromagnetic eventsin the Universe (e.g. Piran et al. 2000). One of the preferred models to ex-plain the long duration (i.e., > 2 s) GRBs is the star core collapse into a blackhole produced in a supernova type SNIb/c explosion (Mac Fayden, Woosley &Heger 2001). This mechanism of GRB formation is also known as the collapsarscenario. This model is linked to the evolution of massive stars which normallyhave a mean lifetime of several million years implying that the typical lifetime ofa GRB progenitor system is negligible in cosmological terms. So, it turns to benatural to consider these events as possible tracers of the cosmic star formationhistory up to high redshifts. In particular, the GRBs would permit to obtaininformation about star formation regions in galactic systems with different levelsof evolution.Recently, Courty et al. (2004) made use of structure formation simulationsin order to identify galactic populations in the simulated sample capable toreproduce the observational features of the observed HGs. These galaxies showa trend to be bluer and sub-luminous (e.g. Le Floc’h et al. 2003). Their analysisseems to confirm the connection with the star formation rate (SFR) if the GRBsevents are formed in galaxies with high star formation efficiency. In this work wedevelop a GRB event generator based on the collapsar model for the progenitorsand study the properties of the HGs in cosmological simulations.2. GRB Montecarlo code and discussionThe GRB event algorithm has been designed to work coupled to numericalsimulations in a cosmological framework. We used the simulated galaxy catalogconstructed by De Rossi et al. (2005) from simulations performed with thechemo-dynamical code of Scannapieco et al. (2005) developed within GADGET-2GRBs host galaxies 461Figure 1. Left: Cosmic SFR density for the simulated box of 10 Mpch−1 comoving size as a function of redshift. Right: Simulated proba-bility for GRBs occurrence as a function of redshift.(Springel & Hernquist 2002). The gas component is followed using the SmoothedParticle Hydrodynamics technique while the dark matter component is followedusing a Tree-Particle Mesh method. This chemo-dynamical code describes theenrichment of the interstellar medium by SNII and SNIa supernova explosions.The cosmological model assumed is defined by the following set of cosmologicalparameters: ΩM = 0.3, ΩΛ = 0.7, Ωb = 0.04 and H0 = 100 h km s−1 Mpc−1 withh = 0.7. The simulations represent a typical region of 10 Mpc h−1 comoving sizewith 2×803 particles which translates into an initial mass resolution of 2×107 Mh−1 and 2×108 M h−1 for the gas and dark matter particles, respectively. Thecatalog of simulated galaxies provides information on the gas, stellar and darkmatter components for the redshift range z = [0, 3]. A Montecarlo-based codewas developed to generate GRBs events in each simulated galaxy of the catalog.We assumed Poissonian statistics to emulate the probability distribution of theGRBs events. The GRB generator selects young stars as possible candidates,where SNIb/c events may occur, and consequently, collapsar events can develope.For that, we adopted a cut-off in stellar ages of tc = 107 yr. A median rate ofcollapsar events (Rcoll) consistent with that estimated by Fryer et al. (1999),Rcoll ∼ 10 − 1000 Myr−1 Galaxy−1 where Galaxy represents a typical galaxy,was assumed. In particular, in this work we used Rcoll = 100 Myr−1 Galaxy−1and a typical galaxy mass of 1011 M. A total of 500 Montecarlo realizationswas perfomed for every selected stellar particle in each simulated galaxy in thecatalog. Our preliminary results can be seen in Figures 1 and 2.Figure 1 shows the simulated comoving SFR density (ρSFR, left panel) and thesimulated probability of GRB event occurrence (right panel) as a function ofredshift. As it can be seen from Figure 1, assuming the collapsar scenario,where GRBs originate from massive stars, produces the expected behaviour ofGRBs being good tracers of the cosmic SFR history. Figure 2 shows the SFRefficiency (SFR, defined as the SFR normalized to the total stellar mass at eachanalysed redshift) versus circular velocities (Vopt) of the HGs from z = 3. It canbe seen from this figure that the SFR efficiency anticorrelates with Vopt, so thatthe higher the efficiency, the smaller the systems (i.e. slower rotating systems).Note that, at all analyzed z, more than 50 per cent of the simulated HGs haveVopt < 100 km s−1. According to the Tully-Fisher relation, this result impliesthat high SFR efficiencies are associated to sub-luminous systems in agreement462 S. E. Nuza et al.Figure 2. SFR efficiency versus circular velocity for the simulatedHGs sample from z = 3 to z = 0.1.with observations. Note also that the SFR efficiency increases with increasingredshifts and that for z > 1, all HGs seem to have similar values.Interesting improvements for the future would be to include an analysis basedon the simulated colours and metallicities of the simulated HGs. Numericalsimulations with higher resolution are also being analysed in order to confirmthese trends.Acknowledgments. Numerical simulations were run on Ingeld and HOPEPC-clusters at IAFE. We acknowledge financial support from CONICET, AN-PCyT, Fundacio´n Antorchas, SECyT-UNC and LENAC network. We also thankthe referee for several comments that helped to improve this contributed paper.ReferencesCourty, S., Bjo¨rnsson, G. & Gudmundsson, E. H., 2004, MNRAS, 354, 581De Rossi, M. E., Tissera, P. B. & Scannapieco, C., 2005, Ap&SS, 329, 15Fryer, C., Woosley, S. E. & Hartmann, D., 1999, ApJ, 526, 152Le Floc’h, E., Duc, P. A., Mirabel, I. F., et al., 2003, A&A, 400, 499MacFadyen, A. I., Woosley, S. E. & Heger, A., 2001, ApJ, 550, 410Piran, T., 2000, Physics Reports, 333, 529Scannapieco C., Tissera P. B., White S. D. M. & Springel V., 2005, MNRAS,364, 552Springel V. & Hernquist L., 2002, MNRAS, 333, 649

Study of the relationship between the gamma ray bursts and their host galaxies

LAReferencia - Red Federada de Repositorios Institucionales de Publicaciones Científicas Latinoamericanas

Asociación Argentina de Astronomı́aBAAA, Vol. 48, 2005E.M. Arnal, A. Brunini, J.J. Clariá Olmedo, J.C. Forte, D.O. Gómez, D. Garćıa Lambas,Z. López Garćıa, S. M. Malaroda, & G.E. Romero, eds.COMUNICACIÓN DE TRABAJO – CONTRIBUTED PAPERStudy of the relationship between the gamma ray burstsand their host galaxiesSebastián E. NuzaInstituto de Astronomı́a y F́ısica del Espacio, Buenos Aires, Argentina;sebasn@iafe.uba.arPatricia B. TisseraInstituto de Astronomı́a y F́ısica del Espacio, Buenos Aires, Argentina;patricia@iafe.uba.arLeonardo J. PellizzaService d’Astrophysique, DSM/DAPNIA, CEA, Saclay, France;leonardo.pellizza@cea.frDiego Garćıa LambasIATE, Observatorio Astronómico de Córdoba, Córdoba, Argentina;dgl@oac.uncor.eduCecilia ScannapiecoInstituto de Astronomı́a y F́ısica del Espacio, Buenos Aires, Argentina;cecilia@iafe.uba.arMaŕıa E. De RossiInstituto de Astronomı́a y F́ısica del Espacio, Buenos Aires, Argentina;derossi@iafe.uba.arAbstract. Gamma ray bursts (GRBs) belong to the most energeticevents in the Universe. Recently, the extragalactic nature of these sourceshas been confirmed with the discovery of several host galaxies (HGs) andthe measurement of their redshifts. To explain the origin of GRBs variousmodels have been proposed, among which the coalescence of compactobjects and the collapsar scenarios are the most representative, being thecollapsar model one of the most accepted to explain the long durationGRBs. A natural consequence of this model is that the GRBs wouldtrace the star formation rate (SFR) of their HGs. In this contributedpaper we present preliminary results of the development of a Montecarlo-based code for collapsar event formation which is coupled to chemical-459460 S. E. Nuza et al.cosmological simulations aiming at studying the properties of HGs in ahierarchical scenario.Resumen. Las explosiones de radiación gamma (ERG) se encuentranentre los eventos más energéticos del Universo. Recientemente, la natu-raleza extragaláctica de estas fuentes fue confirmada con el descubrim-iento de varias de sus galaxias huésped y la medición de sus corrimientosal rojo. Para explicar su origen, varios modelos han sido propuestos, entrelos cuales las colisiones de objetos compactos en sistemas binarios y losllamados collapsars son los más representativos, siendo este último mod-elo uno de los más aceptados para explicar las ERG de larga duración.Una consecuencia natural del mismo es que las ERG trazaŕıan la tasa deformación estelar de sus respectivas galaxias. En esta comunicación sepresentan resultados preliminares del desarrollo de un código Montecarlopara la formación de collapsars en simulaciones qúımico-cosmológicas, conel fin de estudiar las propiedades de sus galaxias huésped en un escenariojerárquico.1. IntroductionThe gamma ray bursts (GRBs) are the most energetic electromagnetic eventsin the Universe (e.g. Piran et al. 2000). One of the preferred models to ex-plain the long duration (i.e., > 2 s) GRBs is the star core collapse into a blackhole produced in a supernova type SNIb/c explosion (Mac Fayden, Woosley &Heger 2001). This mechanism of GRB formation is also known as the collapsarscenario. This model is linked to the evolution of massive stars which normallyhave a mean lifetime of several million years implying that the typical lifetime ofa GRB progenitor system is negligible in cosmological terms. So, it turns to benatural to consider these events as possible tracers of the cosmic star formationhistory up to high redshifts. In particular, the GRBs would permit to obtaininformation about star formation regions in galactic systems with different levelsof evolution.Recently, Courty et al. (2004) made use of structure formation simulationsin order to identify galactic populations in the simulated sample capable toreproduce the observational features of the observed HGs. These galaxies showa trend to be bluer and sub-luminous (e.g. Le Floc’h et al. 2003). Their analysisseems to confirm the connection with the star formation rate (SFR) if the GRBsevents are formed in galaxies with high star formation efficiency. In this work wedevelop a GRB event generator based on the collapsar model for the progenitorsand study the properties of the HGs in cosmological simulations.2. GRB Montecarlo code and discussionThe GRB event algorithm has been designed to work coupled to numericalsimulations in a cosmological framework. We used the simulated galaxy catalogconstructed by De Rossi et al. (2005) from simulations performed with thechemo-dynamical code of Scannapieco et al. (2005) developed within GADGET-2GRBs host galaxies 461Figure 1. Left: Cosmic SFR density for the simulated box of 10 Mpch−1 comoving size as a function of redshift. Right: Simulated proba-bility for GRBs occurrence as a function of redshift.(Springel & Hernquist 2002). The gas component is followed using the SmoothedParticle Hydrodynamics technique while the dark matter component is followedusing a Tree-Particle Mesh method. This chemo-dynamical code describes theenrichment of the interstellar medium by SNII and SNIa supernova explosions.The cosmological model assumed is defined by the following set of cosmologicalparameters: ΩM = 0.3, ΩΛ = 0.7, Ωb = 0.04 and H0 = 100 h km s−1 Mpc−1 withh = 0.7. The simulations represent a typical region of 10 Mpc h−1 comoving sizewith 2×803 particles which translates into an initial mass resolution of 2×107 Mh−1 and 2×108 M h−1 for the gas and dark matter particles, respectively. Thecatalog of simulated galaxies provides information on the gas, stellar and darkmatter components for the redshift range z = [0, 3]. A Montecarlo-based codewas developed to generate GRBs events in each simulated galaxy of the catalog.We assumed Poissonian statistics to emulate the probability distribution of theGRBs events. The GRB generator selects young stars as possible candidates,where SNIb/c events may occur, and consequently, collapsar events can develope.For that, we adopted a cut-off in stellar ages of tc = 107 yr. A median rate ofcollapsar events (Rcoll) consistent with that estimated by Fryer et al. (1999),Rcoll ∼ 10 − 1000 Myr−1 Galaxy−1 where Galaxy represents a typical galaxy,was assumed. In particular, in this work we used Rcoll = 100 Myr−1 Galaxy−1and a typical galaxy mass of 1011 M. A total of 500 Montecarlo realizationswas perfomed for every selected stellar particle in each simulated galaxy in thecatalog. Our preliminary results can be seen in Figures 1 and 2.Figure 1 shows the simulated comoving SFR density (ρSFR, left panel) and thesimulated probability of GRB event occurrence (right panel) as a function ofredshift. As it can be seen from Figure 1, assuming the collapsar scenario,where GRBs originate from massive stars, produces the expected behaviour ofGRBs being good tracers of the cosmic SFR history. Figure 2 shows the SFRefficiency (εSFR, defined as the SFR normalized to the total stellar mass at eachanalysed redshift) versus circular velocities (Vopt) of the HGs from z = 3. It canbe seen from this figure that the SFR efficiency anticorrelates with Vopt, so thatthe higher the efficiency, the smaller the systems (i.e. slower rotating systems).Note that, at all analyzed z, more than 50 per cent of the simulated HGs haveVopt < 100 km s−1. According to the Tully-Fisher relation, this result impliesthat high SFR efficiencies are associated to sub-luminous systems in agreement462 S. E. Nuza et al.Figure 2. SFR efficiency versus circular velocity for the simulatedHGs sample from z = 3 to z = 0.1.with observations. Note also that the SFR efficiency increases with increasingredshifts and that for z > 1, all HGs seem to have similar values.Interesting improvements for the future would be to include an analysis basedon the simulated colours and metallicities of the simulated HGs. Numericalsimulations with higher resolution are also being analysed in order to confirmthese trends.Acknowledgments. Numerical simulations were run on Ingeld and HOPEPC-clusters at IAFE. We acknowledge financial support from CONICET, AN-PCyT, Fundación Antorchas, SECyT-UNC and LENAC network. We also thankthe referee for several comments that helped to improve this contributed paper.ReferencesCourty, S., Björnsson, G. & Gudmundsson, E. H., 2004, MNRAS, 354, 581De Rossi, M. E., Tissera, P. B. & Scannapieco, C., 2005, Ap&SS, 329, 15Fryer, C., Woosley, S. E. & Hartmann, D., 1999, ApJ, 526, 152Le Floc’h, E., Duc, P. A., Mirabel, I. F., et al., 2003, A&A, 400, 499MacFadyen, A. I., Woosley, S. E. & Heger, A., 2001, ApJ, 550, 410Piran, T., 2000, Physics Reports, 333, 529Scannapieco C., Tissera P. B., White S. D. M. & Springel V., 2005, MNRAS,364, 552Springel V. & Hernquist L., 2002, MNRAS, 333, 649

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Study of the relationship between the gamma ray bursts and their host galaxies

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