I. Toledo - Academia.edu (original) (raw)
Papers by I. Toledo
Ground-based and Airborne Telescopes IV, 2012
ABSTRACT The Atacama Large Millimeter/submillimeter Array (ALMA) will consist of at least 54 twel... more ABSTRACT The Atacama Large Millimeter/submillimeter Array (ALMA) will consist of at least 54 twelve-meter antennas and 12 seven-meter antennas operating as an aperture synthesis array in the (sub)millimeter wavelength range. The ALMA System Integration Science Team (SIST) is a group of scientists and data analysts whose primary task is to verify and characterize the astronomical performance of array elements as single dish and interferometric systems. The full set of tasks is required for the initial construction phase verification of every array element, and these can be divided roughly into fundamental antenna performance tests (verification of antenna surface accuracy, basic tracking, switching, and on-the-fly rastering) and astronomical radio verification tasks (radio pointing, focus, basic interferometry, and end-to-end spectroscopic verification). These activities occur both at the Operations Support Facility (just below 3000 m elevation) and at the Array Operations Site at 5000 m.
Proceedings of SPIE - The International Society for Optical Engineering, 2008
The Department of Astronomy and Astrophysics (DAA) of the Pontificia Universidad Católica de Chil... more The Department of Astronomy and Astrophysics (DAA) of the Pontificia Universidad Católica de Chile (PUC) operates a small observatory at Santa Martina hills located in the outskirts of Santiago. Despite the close distance (about 30 km) from the centre of a very large metropolitan area, the observatory offers excellent conditions in terms of number of clear nights and relatively good
Ground-based and Airborne Telescopes IV, 2012
ABSTRACT The Atacama Large Millimeter/submillimeter Array (ALMA) will consist of at least 54 twel... more ABSTRACT The Atacama Large Millimeter/submillimeter Array (ALMA) will consist of at least 54 twelve-meter antennas and 12 seven-meter antennas operating as an aperture synthesis array in the (sub)millimeter wavelength range. The ALMA System Integration Science Team (SIST) is a group of scientists and data analysts whose primary task is to verify and characterize the astronomical performance of array elements as single dish and interferometric systems. The full set of tasks is required for the initial construction phase verification of every array element, and these can be divided roughly into fundamental antenna performance tests (verification of antenna surface accuracy, basic tracking, switching, and on-the-fly rastering) and astronomical radio verification tasks (radio pointing, focus, basic interferometry, and end-to-end spectroscopic verification). These activities occur both at the Operations Support Facility (just below 3000 m elevation) and at the Array Operations Site at 5000 m.
EPJ Web of Conferences, 2012
ABSTRACT The ESO public survey "VISTA Variables in the Via Lactea" (VVV) starte... more ABSTRACT The ESO public survey "VISTA Variables in the Via Lactea" (VVV) started mapping the inner disk and bulge of our Galaxy with the VISTA 4m telescope in the near-IR in 2010. The planned survey area of 520 deg(2) is observed in the Z, Y, J, H and Ks filters, and in addition more than 100 epochs of repeated imaging in Ks will be collected over similar to 5 years. The final products will be a deep near-IR atlas in five passbands, and catalogue of more than a million variable sources. This public survey will provide data available to the whole community and therefore will enable further studies of the history of the Milky Way, its star cluster evolution, and the population census of the Galactic Bulge and center, as well as the investigations of the star formation regions in the disk.
Research in Astronomy and Astrophysics, 2011
We present galaxy spectroscopic data on a pencil beam of 10.75 ′ × 7.5 ′ centered on the X-ray cl... more We present galaxy spectroscopic data on a pencil beam of 10.75 ′ × 7.5 ′ centered on the X-ray cluster RXJ0054.0-2823 at z = 0.29. We study the spectral evolution of galaxies from z = 1 down to the cluster redshift in a magnitude-limited sample at R ≤ 23, for which the statistical properties of the sample are well understood. We divide emission-line galaxies in star-forming galaxies, LINERs, and Seyferts by using emissionline ratios of [OII], Hβ, and [OIII], and derive stellar fractions from population synthesis models. We focus our analysis on absorption and low-ionization galaxies. For absorptionline galaxies we recover the well known result that these galaxies have had no detectable evolution since z ∼ 0.6 − 0.7, but we also find that in the range z = 0.65 − 1 at least 50% of the stars in bright absorption systems are younger than 2.5Gyr. Faint absorption-line galaxies in the cluster at z = 0.29 also had significant star formation during the previous 2-3Gyr, while their brighter counterparts seem to be composed only of old stars. At z ∼ 0.8, our dynamically young cluster had a truncated red-sequence. This result seems to be consistent with a scenario where the final assembly of E/S0 took place at z < 1. In the volume-limited range 0.35 ≤ z ≤ 0.65 we find that 23% of the early-type galaxies have LINER-like spectra with Hβ in absorption and a significant component of A stars. The vast majority of LINERs in our sample have significant populations of young and intermediate-aged stars and are thus not related to AGN, but to the population of 'retired galaxies' recently identified by in the SDSS. Early-type LINERs with various fractions of A stars, and E+A galaxies appear to play an important role in the formation of the red sequence.
New Astronomy, 2010
We describe the public ESO near-IR variability survey (VVV) scanning the Milky Way bulge and an a... more We describe the public ESO near-IR variability survey (VVV) scanning the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high. The survey will take 1929 h of observations with the 4-m VISTA telescope during 5 years (2010-2014), covering 109pointsourcesacrossanareaof520deg2,including33knownglobularclustersand10 9 point sources across an area of 520 deg 2 , including 33 known globular clusters and 109pointsourcesacrossanareaof520deg2,including33knownglobularclustersand350 open clusters. The final product will be a deep near-IR atlas in five passbands (0.9-2.5 lm) and a catalogue of more than 10 6 variable point sources.
Monthly Notices of the Royal Astronomical Society, 2012
A substantial fraction of the total stellar mass in rich clusters of galaxies resides in a diffus... more A substantial fraction of the total stellar mass in rich clusters of galaxies resides in a diffuse intergalactic component usually referred to as the Intra-Cluster Light (ICL). Theoretical models indicate that these intergalactic stars originate mostly from the tidal interaction of the cluster galaxies during the assembly history of the cluster, and that a significant fraction of these stars could have formed in-situ from the late infall of cold metal-poor gas clouds onto the cluster. However, these models also over-predict the fraction of stellar mass in the ICL by a substantial margin, something that is still not well understood. The models also make predictions about the age distribution of the ICL stars, which may provide additional observational constraints. Here we present population synthesis models for the ICL of an intermediate redshift (z=0.29) X-ray cluster that we have extensively studied in previous papers. The advantage of observing intermediate redshift clusters rather than nearby ones is that the former fit the field of view of multi-object spectrographs in 8m telescopes and therefore permit to encompass most of the ICL with only a few well placed slits.
Monthly Notices of the Royal Astronomical Society, 2011
The diffuse intracluster light (ICL) contains a significant fraction of the total stellar mass in... more The diffuse intracluster light (ICL) contains a significant fraction of the total stellar mass in clusters of galaxies, and contributes in roughly equal proportion as the hot intra-cluster medium (ICM) to the total baryon content of clusters. Because of the potential importance of understanding the origin of the ICL in the context of the formation and evolution of structure in the Universe, the field has recently undergone a revival both in the quality and quantity of observational and theoretical investigations. Due to cosmological dimming, the observational work has mostly concentrated on low redshift clusters, but clearly observations at higher redshifts can provide interesting clues about the evolution of the diffuse component. In this paper we present the first results of a program to characterize the ICL of intermediate redshift clusters. We find that at z ∼ 0.3, the X-ray cluster RX J0054.0-2823 already has a significant ICL and that the fraction of the total light in the ICL and the brightest cluster galaxy (BCG) is comparable to that of similar clusters at lower redshift. We also find that the kinematics of the ICL is consistent with it being the remnant of tidally destroyed galaxies streaming in the central regions of the cluster, which has three central giant elliptical galaxies acting as an efficient "grinding machine". Our cluster has a bi-modal radial-velocity distribution and thus two possible values for the velocity dispersion. We find that the cluster fits well in the correlation between BCG+ICL fraction and cluster mass for a range of velocity dispersions, leading us to question the validity of a relevant correlation between these two quantities.
Monthly Notices of the Royal Astronomical Society, 2007
We present high cadence, high precision multi-band photometry of the young, M1Ve, debris disk sta... more We present high cadence, high precision multi-band photometry of the young, M1Ve, debris disk star, AU Microscopii. The data were obtained in three continuum filters spanning a wavelength range from 4500Å to 6600Å, plus Hα, over 28 nights in 2005. The lightcurves show intrinsic stellar variability due to starspots with an amplitude in the blue band of 0.051 magnitudes and a period of 4.847 days. In addition, three large flares were detected in the data which all occur near the minimum brightness of the star. We remove the intrinsic stellar variability and combine the lightcurves of all the filters in order to search for transits by possible planetary companions orbiting in the plane of the nearly edge-on debris disk. The combined final lightcurve has a sampling of 0.35 minutes and a standard deviation of 6.8 millimags (mmag). We performed Monte Carlo simulations by adding fake transits to the observed lightcurve and find with 95% significance that there are no Jupiter mass planets orbiting in the plane of the debris disk on circular orbits with periods, P ≤ 5 days. In addition, there are no young Neptune-like planets (with radii 2.5× smaller than the young Jupiter) on circular orbits with periods, P ≤ 3 days. Barrado y Navascues et al. (1999)), nearby (9.94 ± 0.13 pc, Perryman et al. ) active M-dwarf (M1Ve) star in the β Pictoris moving group which is surrounded by a nearly edge-on circumstellar debris disk . Observations of substructure in the disk suggest the presence of planetary-mass bodies. Such a companion which is close to the star and orbiting in the plane of the disk would transit, causing a dip in brightness. Thus, AU Mic is an excellent target to search for transiting planets in the early stages of formation.
Nature, Jan 16, 2012
η Carinae is one of the most massive binary stars in the Milky Way. It became the second-brightes... more η Carinae is one of the most massive binary stars in the Milky Way. It became the second-brightest star in our sky during its mid-nineteenth-century 'Great Eruption', but then faded from view (with only naked-eye estimates of brightness). Its eruption is unique in that it exceeded the Eddington luminosity limit for ten years. Because it is only 2.3 kiloparsecs away, spatially resolved studies of the nebula have constrained the ejected mass and velocity, indicating that during its nineteenth-century eruption, η Car ejected more than ten solar masses in an event that released ten per cent of the energy of a typical core-collapse supernova, without destroying the star. Here we report observations of light echoes of η Carinae from the 1838-1858 Great Eruption. Spectra of these light echoes show only absorption lines, which are blueshifted by -210 km s(-1), in good agreement with predicted expansion speeds. The light-echo spectra correlate best with those of G2-to-G5 supergiant...
Astronomy & Astrophysics, 2013
Context. There is still some debate about the presence and the morphological properties of the lo... more Context. There is still some debate about the presence and the morphological properties of the long bar in the inner Galaxy. Aims. We investigate the morphological properties of the long Galactic bar using the VVV survey extending star counts at least 3 mag deeper than 2MASS. Our study covers the relatively unexplored negative longitudes of the Galactic bar. We obtain a detailed description of the spatial distribution of star counts towards the long Galactic bar as well as to measure its parameters. Methods. We performed star counts towards −20 • < ℓ < 0, |b| ≤ 2 • using VVV, 2MASS, and GLIMPSE data. We applied an average interstellar extinction correction. We also adjusted latitudinal profiles to obtain the centroid variation and bar thickness. Results. We probe the structure of long Galactic bar, as well as its far edge at ℓ ≈ −14 • . The differences between counts with and without extinction correction allow us to produce a crude extinction map showing regions with high extinction, mainly beyond the end of long Galactic bar. The latitudinal profiles show evidence of the centroid vertical variation with Galactic longitude reaching a minimum at ℓ ≈ −13.8 • . The bar has an inclination angle α = 43 • ± 5 • with respect to the line Sun-Galactic center. In addition, we have determined the bar parameters, such as thickness, length, and stellar distribution.
Astronomy & Astrophysics, 2011
Context. It is not known how many globular clusters may have been left undetected towards the Gal... more Context. It is not known how many globular clusters may have been left undetected towards the Galactic bulge. Aims. One of the aims of the VISTA Variables in the Via Lactea (VVV) Survey is to accurately measure the physical parameters of the known globular clusters in the inner regions of the Milky Way and to search for new ones, hidden in regions of large extinction. Methods. Deep near infrared images give deep JHK S -band photometry of a region surrounding the known globular cluster UKS 1 and reveal a new low-mass globular cluster candidate that we name VVV CL001. Results. We use the horizontal branch red clump in order to measure E(B-V)∼2.2 mag, (m− M) 0 = 16.01 mag, and D=15.9 kpc for the globular cluster UKS 1. Based on the near-infrared colour magnitude diagrams, we also measure that VVV CL001 has E(B-V)∼2.0, and that it is at least as metal-poor as UKS 1, however, its distance remains uncertain. Conclusions. Our finding confirms the previous projection that the central region of the Milky Way harbors more globular clusters. VVV CL001 and UKS 1 are good candidates for a physical cluster binary, but follow-up observations are needed to decide if they are located at the same distance and have similar radial velocities.
Astronomy & Astrophysics, 2011
Context. VISTA Variables in the Vía Láctea (VVV) is one of the six ESO Public Surveys operating o... more Context. VISTA Variables in the Vía Láctea (VVV) is one of the six ESO Public Surveys operating on the new 4-meter Visible and Infrared Survey Telescope for Astronomy (VISTA). VVV is scanning the Milky Way bulge and an adjacent section of the disk, where star formation activity is high. One of the principal goals of the VVV Survey is to find new star clusters of different ages. Aims. In order to trace the early epochs of star cluster formation we concentrated our search in the directions to those of known star formation regions, masers, radio, and infrared sources. Methods. The disk area covered by VVV was visually inspected using the pipeline processed and calibrated KS-band tile images for stellar overdensities. Subsequently, we examined the composite JHKS and ZJKS color images of each candidate. PSF photometry of 15 × 15 arcmin fields centered on the candidates was then performed on the Cambridge Astronomy Survey Unit reduced images. After statistical field-star decontamination, color-magnitude and color-color diagrams were constructed and analyzed. Results. We report the discovery of 96 new infrared open clusters and stellar groups. Most of the new cluster candidates are faint and compact (with small angular sizes), highly reddened, and younger than 5 Myr. For relatively well populated cluster candidates we derived their fundamental parameters such as reddening, distance, and age by fitting the solarmetallicity Padova isochrones to the color-magnitude diagrams.
Astronomy and Astrophysics, 2009
Aims. This study aims at determining the parameters of the three candidate pre-cataclysmic binari... more Aims. This study aims at determining the parameters of the three candidate pre-cataclysmic binaries EC 12477-1738, EC 13349-3237, and EC 14329-1625, most importantly their orbital period. Methods. Time-series photometry reveals orbital modulation in the form of sinusoidal variation due to the reflection effect. Photometric observations are complemented by time-resolved spectroscopy that yields radial velocities of the Hα emission line. The combination of both methods allows us to unambiguously determine the orbital periods. The average spectra are used to estimate physical parameters of the primary and secondary stellar components. Results. We determine the orbital period for EC 12477-1738 as 0.362 d, thus confirming the value previously reported. A similar period, P = 0.350 d, is found for EC 14329-1625. Both systems incorporate a medium-hot white dwarf (T = 15 000 − 20 000 K) and an M3V secondary star. The third pre-CV, EC 13349-3237, is the youngest of the three, with a hot WD (T ∼ 35 000 K), and it also has the longest period P = 0.469 d. It furthermore turns out to be one of the still rare pre-CVs with a comparatively early-type, M1V, secondary star, which will eventually evolve into a CV above the period gap.
Astronomische Nachrichten, 2009
We propose that some high relative velocity dumbbell galaxies are the centers of poor clusters or... more We propose that some high relative velocity dumbbell galaxies are the centers of poor clusters or groups that are coming into a merging process. The components of these galaxies closely follow the incoming velocity of the merging groups, as revealed by the bimodality of the velocity histograms. Only mergers in a direction with a small angle to the line of sight can show the large velocity difference of the components and the velocity separation of incoming subgroups in the histograms. In this case the simple interpretation would be that the dumbbells components are also in an early phase of their merger, as they still keep the information of the incoming orbits, but analysis of a numerous sample is needed to prove this suggestion.
We report on measurements of the extinction in the U, B & V bands and of the NSB (Night Sky Backg... more We report on measurements of the extinction in the U, B & V bands and of the NSB (Night Sky Background) during 2 dark periods on La Silla Observatory and at 4000-5000m on the ALMA site using an UV optimized 25 cm portable telescope. Using Landolt stars we obtained the color equations of our filters in the range of −0.22 < B − V < 1.45, −1.11 < U − B < 1.18, the extinction coefficients within 1 < Z < 2 air masses, and the NSB in U, B & V on La Silla. We measured the transparency of the night sky and the NSB in U, at 4000m asl. on the ALMA road towards the Chajnantor site, and the extinction in U, B & V at 5000m on the Chajnantor plateau. We also obtained some NSB measurements at 5000m in U under variable sky conditions.
We carried out a VVV J, H and Ks survey of infrared star clusters in the Milky Way southern disk ... more We carried out a VVV J, H and Ks survey of infrared star clusters in the Milky Way southern disk area. We concentrated efforts on embedded clusters, which are those expected in the areas of known star formation regions, masers, radio, and infrared sources. The present study provides 96 new infrared clusters and stellar groups. (1 data file).
Ground-based and Airborne Telescopes IV, 2012
ABSTRACT The Atacama Large Millimeter/submillimeter Array (ALMA) will consist of at least 54 twel... more ABSTRACT The Atacama Large Millimeter/submillimeter Array (ALMA) will consist of at least 54 twelve-meter antennas and 12 seven-meter antennas operating as an aperture synthesis array in the (sub)millimeter wavelength range. The ALMA System Integration Science Team (SIST) is a group of scientists and data analysts whose primary task is to verify and characterize the astronomical performance of array elements as single dish and interferometric systems. The full set of tasks is required for the initial construction phase verification of every array element, and these can be divided roughly into fundamental antenna performance tests (verification of antenna surface accuracy, basic tracking, switching, and on-the-fly rastering) and astronomical radio verification tasks (radio pointing, focus, basic interferometry, and end-to-end spectroscopic verification). These activities occur both at the Operations Support Facility (just below 3000 m elevation) and at the Array Operations Site at 5000 m.
Proceedings of SPIE - The International Society for Optical Engineering, 2008
The Department of Astronomy and Astrophysics (DAA) of the Pontificia Universidad Católica de Chil... more The Department of Astronomy and Astrophysics (DAA) of the Pontificia Universidad Católica de Chile (PUC) operates a small observatory at Santa Martina hills located in the outskirts of Santiago. Despite the close distance (about 30 km) from the centre of a very large metropolitan area, the observatory offers excellent conditions in terms of number of clear nights and relatively good
Ground-based and Airborne Telescopes IV, 2012
ABSTRACT The Atacama Large Millimeter/submillimeter Array (ALMA) will consist of at least 54 twel... more ABSTRACT The Atacama Large Millimeter/submillimeter Array (ALMA) will consist of at least 54 twelve-meter antennas and 12 seven-meter antennas operating as an aperture synthesis array in the (sub)millimeter wavelength range. The ALMA System Integration Science Team (SIST) is a group of scientists and data analysts whose primary task is to verify and characterize the astronomical performance of array elements as single dish and interferometric systems. The full set of tasks is required for the initial construction phase verification of every array element, and these can be divided roughly into fundamental antenna performance tests (verification of antenna surface accuracy, basic tracking, switching, and on-the-fly rastering) and astronomical radio verification tasks (radio pointing, focus, basic interferometry, and end-to-end spectroscopic verification). These activities occur both at the Operations Support Facility (just below 3000 m elevation) and at the Array Operations Site at 5000 m.
EPJ Web of Conferences, 2012
ABSTRACT The ESO public survey "VISTA Variables in the Via Lactea" (VVV) starte... more ABSTRACT The ESO public survey "VISTA Variables in the Via Lactea" (VVV) started mapping the inner disk and bulge of our Galaxy with the VISTA 4m telescope in the near-IR in 2010. The planned survey area of 520 deg(2) is observed in the Z, Y, J, H and Ks filters, and in addition more than 100 epochs of repeated imaging in Ks will be collected over similar to 5 years. The final products will be a deep near-IR atlas in five passbands, and catalogue of more than a million variable sources. This public survey will provide data available to the whole community and therefore will enable further studies of the history of the Milky Way, its star cluster evolution, and the population census of the Galactic Bulge and center, as well as the investigations of the star formation regions in the disk.
Research in Astronomy and Astrophysics, 2011
We present galaxy spectroscopic data on a pencil beam of 10.75 ′ × 7.5 ′ centered on the X-ray cl... more We present galaxy spectroscopic data on a pencil beam of 10.75 ′ × 7.5 ′ centered on the X-ray cluster RXJ0054.0-2823 at z = 0.29. We study the spectral evolution of galaxies from z = 1 down to the cluster redshift in a magnitude-limited sample at R ≤ 23, for which the statistical properties of the sample are well understood. We divide emission-line galaxies in star-forming galaxies, LINERs, and Seyferts by using emissionline ratios of [OII], Hβ, and [OIII], and derive stellar fractions from population synthesis models. We focus our analysis on absorption and low-ionization galaxies. For absorptionline galaxies we recover the well known result that these galaxies have had no detectable evolution since z ∼ 0.6 − 0.7, but we also find that in the range z = 0.65 − 1 at least 50% of the stars in bright absorption systems are younger than 2.5Gyr. Faint absorption-line galaxies in the cluster at z = 0.29 also had significant star formation during the previous 2-3Gyr, while their brighter counterparts seem to be composed only of old stars. At z ∼ 0.8, our dynamically young cluster had a truncated red-sequence. This result seems to be consistent with a scenario where the final assembly of E/S0 took place at z < 1. In the volume-limited range 0.35 ≤ z ≤ 0.65 we find that 23% of the early-type galaxies have LINER-like spectra with Hβ in absorption and a significant component of A stars. The vast majority of LINERs in our sample have significant populations of young and intermediate-aged stars and are thus not related to AGN, but to the population of 'retired galaxies' recently identified by in the SDSS. Early-type LINERs with various fractions of A stars, and E+A galaxies appear to play an important role in the formation of the red sequence.
New Astronomy, 2010
We describe the public ESO near-IR variability survey (VVV) scanning the Milky Way bulge and an a... more We describe the public ESO near-IR variability survey (VVV) scanning the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high. The survey will take 1929 h of observations with the 4-m VISTA telescope during 5 years (2010-2014), covering 109pointsourcesacrossanareaof520deg2,including33knownglobularclustersand10 9 point sources across an area of 520 deg 2 , including 33 known globular clusters and 109pointsourcesacrossanareaof520deg2,including33knownglobularclustersand350 open clusters. The final product will be a deep near-IR atlas in five passbands (0.9-2.5 lm) and a catalogue of more than 10 6 variable point sources.
Monthly Notices of the Royal Astronomical Society, 2012
A substantial fraction of the total stellar mass in rich clusters of galaxies resides in a diffus... more A substantial fraction of the total stellar mass in rich clusters of galaxies resides in a diffuse intergalactic component usually referred to as the Intra-Cluster Light (ICL). Theoretical models indicate that these intergalactic stars originate mostly from the tidal interaction of the cluster galaxies during the assembly history of the cluster, and that a significant fraction of these stars could have formed in-situ from the late infall of cold metal-poor gas clouds onto the cluster. However, these models also over-predict the fraction of stellar mass in the ICL by a substantial margin, something that is still not well understood. The models also make predictions about the age distribution of the ICL stars, which may provide additional observational constraints. Here we present population synthesis models for the ICL of an intermediate redshift (z=0.29) X-ray cluster that we have extensively studied in previous papers. The advantage of observing intermediate redshift clusters rather than nearby ones is that the former fit the field of view of multi-object spectrographs in 8m telescopes and therefore permit to encompass most of the ICL with only a few well placed slits.
Monthly Notices of the Royal Astronomical Society, 2011
The diffuse intracluster light (ICL) contains a significant fraction of the total stellar mass in... more The diffuse intracluster light (ICL) contains a significant fraction of the total stellar mass in clusters of galaxies, and contributes in roughly equal proportion as the hot intra-cluster medium (ICM) to the total baryon content of clusters. Because of the potential importance of understanding the origin of the ICL in the context of the formation and evolution of structure in the Universe, the field has recently undergone a revival both in the quality and quantity of observational and theoretical investigations. Due to cosmological dimming, the observational work has mostly concentrated on low redshift clusters, but clearly observations at higher redshifts can provide interesting clues about the evolution of the diffuse component. In this paper we present the first results of a program to characterize the ICL of intermediate redshift clusters. We find that at z ∼ 0.3, the X-ray cluster RX J0054.0-2823 already has a significant ICL and that the fraction of the total light in the ICL and the brightest cluster galaxy (BCG) is comparable to that of similar clusters at lower redshift. We also find that the kinematics of the ICL is consistent with it being the remnant of tidally destroyed galaxies streaming in the central regions of the cluster, which has three central giant elliptical galaxies acting as an efficient "grinding machine". Our cluster has a bi-modal radial-velocity distribution and thus two possible values for the velocity dispersion. We find that the cluster fits well in the correlation between BCG+ICL fraction and cluster mass for a range of velocity dispersions, leading us to question the validity of a relevant correlation between these two quantities.
Monthly Notices of the Royal Astronomical Society, 2007
We present high cadence, high precision multi-band photometry of the young, M1Ve, debris disk sta... more We present high cadence, high precision multi-band photometry of the young, M1Ve, debris disk star, AU Microscopii. The data were obtained in three continuum filters spanning a wavelength range from 4500Å to 6600Å, plus Hα, over 28 nights in 2005. The lightcurves show intrinsic stellar variability due to starspots with an amplitude in the blue band of 0.051 magnitudes and a period of 4.847 days. In addition, three large flares were detected in the data which all occur near the minimum brightness of the star. We remove the intrinsic stellar variability and combine the lightcurves of all the filters in order to search for transits by possible planetary companions orbiting in the plane of the nearly edge-on debris disk. The combined final lightcurve has a sampling of 0.35 minutes and a standard deviation of 6.8 millimags (mmag). We performed Monte Carlo simulations by adding fake transits to the observed lightcurve and find with 95% significance that there are no Jupiter mass planets orbiting in the plane of the debris disk on circular orbits with periods, P ≤ 5 days. In addition, there are no young Neptune-like planets (with radii 2.5× smaller than the young Jupiter) on circular orbits with periods, P ≤ 3 days. Barrado y Navascues et al. (1999)), nearby (9.94 ± 0.13 pc, Perryman et al. ) active M-dwarf (M1Ve) star in the β Pictoris moving group which is surrounded by a nearly edge-on circumstellar debris disk . Observations of substructure in the disk suggest the presence of planetary-mass bodies. Such a companion which is close to the star and orbiting in the plane of the disk would transit, causing a dip in brightness. Thus, AU Mic is an excellent target to search for transiting planets in the early stages of formation.
Nature, Jan 16, 2012
η Carinae is one of the most massive binary stars in the Milky Way. It became the second-brightes... more η Carinae is one of the most massive binary stars in the Milky Way. It became the second-brightest star in our sky during its mid-nineteenth-century 'Great Eruption', but then faded from view (with only naked-eye estimates of brightness). Its eruption is unique in that it exceeded the Eddington luminosity limit for ten years. Because it is only 2.3 kiloparsecs away, spatially resolved studies of the nebula have constrained the ejected mass and velocity, indicating that during its nineteenth-century eruption, η Car ejected more than ten solar masses in an event that released ten per cent of the energy of a typical core-collapse supernova, without destroying the star. Here we report observations of light echoes of η Carinae from the 1838-1858 Great Eruption. Spectra of these light echoes show only absorption lines, which are blueshifted by -210 km s(-1), in good agreement with predicted expansion speeds. The light-echo spectra correlate best with those of G2-to-G5 supergiant...
Astronomy & Astrophysics, 2013
Context. There is still some debate about the presence and the morphological properties of the lo... more Context. There is still some debate about the presence and the morphological properties of the long bar in the inner Galaxy. Aims. We investigate the morphological properties of the long Galactic bar using the VVV survey extending star counts at least 3 mag deeper than 2MASS. Our study covers the relatively unexplored negative longitudes of the Galactic bar. We obtain a detailed description of the spatial distribution of star counts towards the long Galactic bar as well as to measure its parameters. Methods. We performed star counts towards −20 • < ℓ < 0, |b| ≤ 2 • using VVV, 2MASS, and GLIMPSE data. We applied an average interstellar extinction correction. We also adjusted latitudinal profiles to obtain the centroid variation and bar thickness. Results. We probe the structure of long Galactic bar, as well as its far edge at ℓ ≈ −14 • . The differences between counts with and without extinction correction allow us to produce a crude extinction map showing regions with high extinction, mainly beyond the end of long Galactic bar. The latitudinal profiles show evidence of the centroid vertical variation with Galactic longitude reaching a minimum at ℓ ≈ −13.8 • . The bar has an inclination angle α = 43 • ± 5 • with respect to the line Sun-Galactic center. In addition, we have determined the bar parameters, such as thickness, length, and stellar distribution.
Astronomy & Astrophysics, 2011
Context. It is not known how many globular clusters may have been left undetected towards the Gal... more Context. It is not known how many globular clusters may have been left undetected towards the Galactic bulge. Aims. One of the aims of the VISTA Variables in the Via Lactea (VVV) Survey is to accurately measure the physical parameters of the known globular clusters in the inner regions of the Milky Way and to search for new ones, hidden in regions of large extinction. Methods. Deep near infrared images give deep JHK S -band photometry of a region surrounding the known globular cluster UKS 1 and reveal a new low-mass globular cluster candidate that we name VVV CL001. Results. We use the horizontal branch red clump in order to measure E(B-V)∼2.2 mag, (m− M) 0 = 16.01 mag, and D=15.9 kpc for the globular cluster UKS 1. Based on the near-infrared colour magnitude diagrams, we also measure that VVV CL001 has E(B-V)∼2.0, and that it is at least as metal-poor as UKS 1, however, its distance remains uncertain. Conclusions. Our finding confirms the previous projection that the central region of the Milky Way harbors more globular clusters. VVV CL001 and UKS 1 are good candidates for a physical cluster binary, but follow-up observations are needed to decide if they are located at the same distance and have similar radial velocities.
Astronomy & Astrophysics, 2011
Context. VISTA Variables in the Vía Láctea (VVV) is one of the six ESO Public Surveys operating o... more Context. VISTA Variables in the Vía Láctea (VVV) is one of the six ESO Public Surveys operating on the new 4-meter Visible and Infrared Survey Telescope for Astronomy (VISTA). VVV is scanning the Milky Way bulge and an adjacent section of the disk, where star formation activity is high. One of the principal goals of the VVV Survey is to find new star clusters of different ages. Aims. In order to trace the early epochs of star cluster formation we concentrated our search in the directions to those of known star formation regions, masers, radio, and infrared sources. Methods. The disk area covered by VVV was visually inspected using the pipeline processed and calibrated KS-band tile images for stellar overdensities. Subsequently, we examined the composite JHKS and ZJKS color images of each candidate. PSF photometry of 15 × 15 arcmin fields centered on the candidates was then performed on the Cambridge Astronomy Survey Unit reduced images. After statistical field-star decontamination, color-magnitude and color-color diagrams were constructed and analyzed. Results. We report the discovery of 96 new infrared open clusters and stellar groups. Most of the new cluster candidates are faint and compact (with small angular sizes), highly reddened, and younger than 5 Myr. For relatively well populated cluster candidates we derived their fundamental parameters such as reddening, distance, and age by fitting the solarmetallicity Padova isochrones to the color-magnitude diagrams.
Astronomy and Astrophysics, 2009
Aims. This study aims at determining the parameters of the three candidate pre-cataclysmic binari... more Aims. This study aims at determining the parameters of the three candidate pre-cataclysmic binaries EC 12477-1738, EC 13349-3237, and EC 14329-1625, most importantly their orbital period. Methods. Time-series photometry reveals orbital modulation in the form of sinusoidal variation due to the reflection effect. Photometric observations are complemented by time-resolved spectroscopy that yields radial velocities of the Hα emission line. The combination of both methods allows us to unambiguously determine the orbital periods. The average spectra are used to estimate physical parameters of the primary and secondary stellar components. Results. We determine the orbital period for EC 12477-1738 as 0.362 d, thus confirming the value previously reported. A similar period, P = 0.350 d, is found for EC 14329-1625. Both systems incorporate a medium-hot white dwarf (T = 15 000 − 20 000 K) and an M3V secondary star. The third pre-CV, EC 13349-3237, is the youngest of the three, with a hot WD (T ∼ 35 000 K), and it also has the longest period P = 0.469 d. It furthermore turns out to be one of the still rare pre-CVs with a comparatively early-type, M1V, secondary star, which will eventually evolve into a CV above the period gap.
Astronomische Nachrichten, 2009
We propose that some high relative velocity dumbbell galaxies are the centers of poor clusters or... more We propose that some high relative velocity dumbbell galaxies are the centers of poor clusters or groups that are coming into a merging process. The components of these galaxies closely follow the incoming velocity of the merging groups, as revealed by the bimodality of the velocity histograms. Only mergers in a direction with a small angle to the line of sight can show the large velocity difference of the components and the velocity separation of incoming subgroups in the histograms. In this case the simple interpretation would be that the dumbbells components are also in an early phase of their merger, as they still keep the information of the incoming orbits, but analysis of a numerous sample is needed to prove this suggestion.
We report on measurements of the extinction in the U, B & V bands and of the NSB (Night Sky Backg... more We report on measurements of the extinction in the U, B & V bands and of the NSB (Night Sky Background) during 2 dark periods on La Silla Observatory and at 4000-5000m on the ALMA site using an UV optimized 25 cm portable telescope. Using Landolt stars we obtained the color equations of our filters in the range of −0.22 < B − V < 1.45, −1.11 < U − B < 1.18, the extinction coefficients within 1 < Z < 2 air masses, and the NSB in U, B & V on La Silla. We measured the transparency of the night sky and the NSB in U, at 4000m asl. on the ALMA road towards the Chajnantor site, and the extinction in U, B & V at 5000m on the Chajnantor plateau. We also obtained some NSB measurements at 5000m in U under variable sky conditions.
We carried out a VVV J, H and Ks survey of infrared star clusters in the Milky Way southern disk ... more We carried out a VVV J, H and Ks survey of infrared star clusters in the Milky Way southern disk area. We concentrated efforts on embedded clusters, which are those expected in the areas of known star formation regions, masers, radio, and infrared sources. The present study provides 96 new infrared clusters and stellar groups. (1 data file).