Tracing the assembly history of NGC 1395 through its Globular Cluster System

We used deep Gemini-South/GMOS g'r'i'z' images to study the globular cluster (GC) system of the massive elliptical galaxy NGC1395, located in the Eridanus supergroup. The photometric analysis of the GC candidates reveals a clear colour bimodality distribution, indicating the presence of 'blue' and 'red' GC subpopulations. While a negative radial colour gradient is detected in the projected spatial distribution of the red GCs, the blue GCs display a shallow colour gradient. The blue GCs also display a remarkable shallow and extended surface density profile, suggesting a significant accretion of low-mass satellites in the outer halo of the galaxy. In addition, the slope of the projected spatial distribution of the blue GCs in the outer regions of the galaxy, is similar to that of the X-ray halo emission. Integrating up to 165 kpc the profile of the projected spatial distribution of the GCs, we estimated a total GC population and specific frequency of 6000 ± 1100 and S N = 7.4 ± 1.4, respectively. Regarding NGC1395 itself, the analysis of the deep Gemini/GMOS images shows a low surface brightness umbrella-like structure indicating, at least, one recent merger event. Through relations recently published in the literature, we obtained global parameters, such as M stellar = 9.32 × 10 11 M⊙ and M h = 6.46 × 10 13 M⊙. Using public spectroscopic data, we derive stellar population parameters of the central region of the galaxy by the full spectral fitting technique. We have found that this region seems to be dominated for an old stellar population, in contrast to findings of young stellar populations from the literature.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

Tracing the assembly history of NGC 1395 through its Globular Cluster System

We used deep Gemini-South/GMOS g'r'i'z' images to study the globular cluster (GC) system of the massive elliptical galaxy NGC1395, located in the Eridanus supergroup. The photometric analysis of the GC candidates reveals a clear colour bimodality distribution, indicating the presence of 'blue' and 'red' GC subpopulations. While a negative radial colour gradient is detected in the projected spatial distribution of the red GCs, the blue GCs display a shallow colour gradient. The blue GCs also display a remarkable shallow and extended surface density profile, suggesting a significant accretion of low-mass satellites in the outer halo of the galaxy. In addition, the slope of the projected spatial distribution of the blue GCs in the outer regions of the galaxy, is similar to that of the X-ray halo emission. Integrating up to 165 kpc the profile of the projected spatial distribution of the GCs, we estimated a total GC population and specific frequency of 6000 ± 1100 and S N = 7.4 ± 1.4, respectively. Regarding NGC1395 itself, the analysis of the deep Gemini/GMOS images shows a low surface brightness umbrella-like structure indicating, at least, one recent merger event. Through relations recently published in the literature, we obtained global parameters, such as M stellar = 9.32 × 10 11 M⊙ and M h = 6.46 × 10 13 M⊙. Using public spectroscopic data, we derive stellar population parameters of the central region of the galaxy by the full spectral fitting technique. We have found that this region seems to be dominated for an old stellar population, in contrast to findings of young stellar populations from the literature.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

The Recovery Phase after the 2009.0-event of η Carinae

The 5.5 years periodicity of eta Carinae is manifested in the "events" observed in different wavelength ranges. The last of these "events" occurred as expected in 2009.0. Our ground-based photometric campaign registered this "event" which showed an "eclipse-like" feature. After that, we continued the observations in order to get information about the post-event behaviour. Our monitoring program consists of daily CCD photometry, obtained using the 0.8 m "Virpi S. Niemela" telescope at La Plata Observatory, and a BVRI and H_alpha filter set. The light curves and photometric data collected during the second half of our 2009 observing season are presented in this paper.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

A Supra-galactic Conundrum: The Globular Clusters Colour Pattern in Virgo Galaxies

The presence of systematic modulations in the colour distributions in composite samples of globular clusters (GCs) associated with galaxies in the Virgo and Fornax clusters has been reported in a previous work. In this paper, we focus on the 27 brightest galaxies in Virgo, and in particular on NGC 4486, the dominant system in terms of GC population. The new analysis includes ≈ 7600 cluster candidates brighter than g = 24.5 (or T1 ≈ 23.70). The results indicate the presence of the characteristic Virgo pattern in these galaxies and that this pattern is detectable over a galactocentric range from 3 to 30 kpc in NGC 4486. This finding gives more support to the idea that the pattern has been the result of an external, still not identified phenomenon, capable of synchronizing the cluster formation in a kind of viral process, and on supragalactic scales (also having, presumably, an impact on the overall star formation history in the entire Virgo cluster).Fil: Forte, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; ArgentinaFil: Cellone, Sergio Aldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; 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; ArgentinaFil: Escudero, Carlos Gabriel. 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: Faifer, Favio Raúl. 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: Geisler, Douglas. Universidad de La Serena; ChileFil: González, Nélida M.. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Scalia, María Cecilia. 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: Sesto, Leandro Alberto. 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: Smith Castelli, Analia Viviana. 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: Vega, Ema Irene. 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; Argentin

Distinguishing circumstellar from stellar photometric variability in Eta Carinae

The interacting binary Eta Carinae remains one of the most enigmatic massive stars in our Galaxy despite over four centuries of observations. In this work, its light curve from the ultraviolet to the near-infrared is analysed using spatially resolved HST observations and intense monitoring at the La Plata Observatory, combined with previously published photometry. We have developed a method to separate the central stellar object in the ground-based images using HST photometry and applying it to the more numerous ground-based data, which supports the hypothesis that the central source is brightening faster than the almost-constant Homunculus. After detrending from long-term brightening, the light curve shows periodic orbital modulation (V ∼ 0.6 mag) attributed to the wind–wind collision cavity as it sweeps around the primary star and it shows variable projected area to our line-of-sight. Two quasi-periodic components with time-scales of 2–3 and 8–10 yr and low amplitude, V < 0.2 mag, are superimposed on the brightening light curve, being the only stellar component of variability found, which indicates minimal stellar instability. Moreover, the light-curve analysis shows no evidence of ‘shell ejections’ at periastron. We propose that the long-term brightening of the stellar core is due to the dissipation of a dusty clump in front of the central star, which works like a natural coronagraph. Thus, the central stars appear to be more stable than previously thought since the dominant variability originates from a changing circumstellar medium. We predict that the brightening phase, due mainly to dust dissipation, will be completed around 2032 ± 4 yr, when the star will be brighter than in the 1600s by up to V ∼ 1 mag.Fil: Damineli, A.. Universidade do Sao Paulo. Instituto de Astronomia, Geofísica e Ciências Atmosféricas; BrasilFil: Fernandez Lajus, Eduardo Eusebio. 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: Almeida, L.A.. Universidade do Sao Paulo. Instituto de Astronomia, Geofísica e Ciências Atmosféricas; Brasil. Universidade Federal do Rio Grande do Norte; BrasilFil: Corcoran, M.F.. National Aeronautics and Space Administration; Estados Unidos. The Catholic University of America; Estados UnidosFil: Damineli, D.S.C.. University of Maryland; Estados UnidosFil: Gull, T.R.. National Aeronautics and Space Administration; Estados UnidosFil: Hamaguchi, K. National Aeronautics and Space Administration; Estados Unidos. University of Maryland; Estados UnidosFil: Hillier, D.J.. University of Pittsburgh; Estados UnidosFil: Jablonski, F.J.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Madura, T.I.. San Jose State University; Estados UnidosFil: Moffat, A.F.J.. Université du Québec a Montreal; CanadáFil: Navarete, F.. Universidade do Sao Paulo. Instituto de Astronomia, Geofísica e Ciências Atmosféricas; BrasilFil: Richardson, N.D.. University Of Toledo (utoledo); Estados UnidosFil: Ruiz, G.F.. Universidade do Sao Paulo. Instituto de Astronomia, Geofísica e Ciências Atmosféricas; BrasilFil: Salerno, N.E.. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Scalia, María Cecilia. 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: Weigelt, G.. Max Planck Institute For Radio Astronomy; Alemani

Análisis de los índices de Lick en el cúmulo de Coma

Se presenta aquí el análisis de la relación color-magnitud (RCM) o secuencia roja (SR) del cúmulo de Coma, a través de la obtención de los índices de Lick. La RCM o SR es una relación fotométrica que ha sido analizada y discutida desde hace ya más de 60 años. Se conoce que la misma representa, principalmente, una relación masa-metalicidad y que además muestra pendientes y dispersiones similares en diversos medioambientes. Sin embargo, se desconoce aún de qué manera las diferentes especies químicas contribuyen a la definición y ubicación de cada galaxia en esta relación. En trabajos anteriores, hemos encontrado que en el cúmulo de Virgo pareciera existir un cierto grado de dependencia del color (g-z) con algunos de los mencionados índices, dependencia que no se detecta en una muestra de galaxias de tipo temprano ubicadas en la zona del cielo denominada Stripe-82. Nos preguntamos si la detección de tales dependencias en el cúmulo de Virgo y no en la región del Stripe-82 estaría indicando que las mismas se originan en efectos de medioambiente. Para intentar responder a este interrogante, analizamos una muestra de 154 galaxias pertenecientes al cúmulo de Coma, a través de sus espectros obtenidos de la base de datos del Sloan Digital Sky Survey (SDSS). Encontramos que el comportamiento de dichos índices para la muestra del Cúmulo de Coma resulta similar a la del Cúmulo de Virgo, pero extendido hacia luminosidades mayores, indicando dependencias similares en ambientes de cúmulos.We present here the analysis of the color-magnitude relation (CMR) or red sequence (RS) of the Coma cluster, by obtaining the Lick indices. The CMR or RS is a photometric relation that has been analyzed and discussed for more than 60 years. It is known that it mainly represents a mass-metallicity relationship and that it also shows similar slopes and dispersions in different environments. However, it is still unknown how the different chemical species contribute to the definition and location of each galaxy in this relation. In previous work, we have found that in the Virgo cluster there seems to be some degree of color (g-z) dependence on some of the above indices, a dependence that is not detected in a sample of early-type galaxies located in the Stripe-82 region of the sky. We wonder if the detection of such dependencies in the Virgo cluster and not in the Stripe-82 region would indicate that they originate from environmental effects. To try to answer this question, we analyzed a sample of 154 galaxies belonging to the Coma cluster, through their spectra obtained from the Sloan Digital Sky Survey (SDSS) database. We find that the behavior of these indices for the Coma Cluster sample is similar to that of the Virgo Cluster, but extended towards higher luminosities, indicating similar dependencies in cluster environments.Asociación Argentina de AstronomíaInstituto de Astrofísica de La Plat

The Recovery Phase after the 2009.0-event of eta Carinae

The 5.5 years periodicity of eta Carinae is manifested in the "events" observed in different wavelength ranges. The last of these "events" occurred as expected in 2009.0. Our ground-based photometric campaign registered this "event" which showed an "eclipse-like" feature. After that, we continued the observations in order to get information about the post-event behaviour. Our monitoring program consists of daily CCD photometry, obtained using the 0.8 m "Virpi S. Niemela" telescope at La Plata Observatory, and a BVRI and H_alpha filter set. The light curves and photometric data collected during the second half of our 2009 observing season are presented in this paper.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Tracing the assembly history of NGC 1395 through its Globular Cluster System

We used deep Gemini-South/GMOS g'r'i'z' images to study the globular cluster (GC) system of the massive elliptical galaxy NGC1395, located in the Eridanus supergroup. The photometric analysis of the GC candidates reveals a clear colour bimodality distribution, indicating the presence of 'blue' and 'red' GC subpopulations. While a negative radial colour gradient is detected in the projected spatial distribution of the red GCs, the blue GCs display a shallow colour gradient. The blue GCs also display a remarkable shallow and extended surface density profile, suggesting a significant accretion of low-mass satellites in the outer halo of the galaxy. In addition, the slope of the projected spatial distribution of the blue GCs in the outer regions of the galaxy, is similar to that of the X-ray halo emission. Integrating up to 165 kpc the profile of the projected spatial distribution of the GCs, we estimated a total GC population and specific frequency of 6000 ± 1100 and S N = 7.4 ± 1.4, respectively. Regarding NGC1395 itself, the analysis of the deep Gemini/GMOS images shows a low surface brightness umbrella-like structure indicating, at least, one recent merger event. Through relations recently published in the literature, we obtained global parameters, such as M stellar = 9.32 × 10 11 M⊙ and M h = 6.46 × 10 13 M⊙. Using public spectroscopic data, we derive stellar population parameters of the central region of the galaxy by the full spectral fitting technique. We have found that this region seems to be dominated for an old stellar population, in contrast to findings of young stellar populations from the literature.Fil: Escudero, Carlos Gabriel. 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: Faifer, Favio Raúl. 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: Smith Castelli, Analia Viviana. 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: Forte, Juan Carlos. 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: Sesto, Leandro Alberto. 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: Gonzalez, N. M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; ArgentinaFil: Scalia, María Cecilia. 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; Argentin

The Recovery Phase after the 2009.0-event of eta Carinae

The 5.5 years periodicity of eta Carinae is manifested in the "events" observed in different wavelength ranges. The last of these "events" occurred as expected in 2009.0. Our ground-based photometric campaign registered this "event" which showed an "eclipse-like" feature. After that, we continued the observations in order to get information about the post-event behaviour. Our monitoring program consists of daily CCD photometry, obtained using the 0.8 m "Virpi S. Niemela" telescope at La Plata Observatory, and a BVRI and H_alpha filter set. The light curves and photometric data collected during the second half of our 2009 observing season are presented in this paper.Fil: Fernandez Lajus, Eduardo Eusebio. 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: Fariña, Cecilia. 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: Schwartz, Martin Alejandro. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Giudici Michilini, Federico Nicolás. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Salerno Ercolani, Nicolas Maria. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Scalia, María Cecilia. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Peri, Cintia Soledad. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: von Essen, Carolina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Calderón, Juan Pablo. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin

Distinguishing circumstellar from stellar photometric variability in Eta Carinae

The interacting binary Eta Carinae remains one of the most enigmatic massive stars in our Galaxy despite over four centuries of observations. In this work, its light curve from the ultraviolet to the near-infrared is analysed using spatially resolved HST observations and intense monitoring at the La Plata Observatory, combined with previously published photometry. We have developed a method to separate the central stellar object in the ground-based images using HST photometry and applying it to the more numerous ground-based data, which supports the hypothesis that the central source is brightening faster than the almost-constant Homunculus. After detrending from long-term brightening, the light curve shows periodic orbital modulation (ΔV ∼ 0.6 mag) attributed to the wind–wind collision cavity as it sweeps around the primary star and it shows variable projected area to our line-of-sight. Two quasi-periodic components with time-scales of 2–3 and 8–10 yr and low amplitude, ΔV &lt; 0.2 mag, are superimposed on the brightening light curve, being the only stellar component of variability found, which indicates minimal stellar instability. Moreover, the light-curve analysis shows no evidence of ‘shell ejections’ at periastron. We propose that the long-term brightening of the stellar core is due to the dissipation of a dusty clump in front of the central star, which works like a natural coronagraph. Thus, the central stars appear to be more stable than previously thought since the dominant variability originates from a changing circumstellar medium. We predict that the brightening phase, due mainly to dust dissipation, will be completed around 2032 ± 4 yr, when the star will be brighter than in the 1600s by up to ΔV ∼ 1 mag.Instituto de Astrofísica de La Plat