About the linearity of the color-magnitude relation of early-type galaxies in the Virgo cluster

We revisit the color-magnitude relation (CMR) of the Virgo cluster early-type galaxies in order to explore its alleged non-linearity. To this aim, we reanalyze the relation already published from data obtained within the ACS Virgo Cluster Survey of the Hubble Space Telescope, and perform our own photometry and analysis of the images of the 100 early-type galaxies observed as part of this survey. In addition, we compare our results with those reported in the literature from data of the Sloan Digital Sky Survey. We have found that when the brightest galaxies and untypical systems are excluded from the sample, a linear relation arises in agreement with what is observed in other groups and clusters. The central regions of the brightest galaxies also follow this relation. In addition, we notice that Virgo contains at least four compact elliptical galaxies besides the well known object VCC 1297 (NGC 4486B). Their locations in the -luminosity diagram define a different trend to that followed by normal early-type dwarf galaxies, setting an upper limit in effective surface brightness and a lower limit in effective radius for their luminosities. Based on the distribution of different galaxy sub-samples in the color-magnitude and -luminosity diagrams we draw some conclusions on their formation and the history of their evolution.Comment: 21 pages, 4 figures, 2 tables. Accepted for publication in Ap

The Brazil-Argentina gemini group for the study of globular cluster systems (BAGGs GCs): Flamingos-2 and GMOS data for NGC 1395

In this letter, we present preliminary results of the analysis of Flamingos-2 and GMOS-S photometry of the globular cluster (GC) system of the elliptical galaxy NGC1395. This is the first step of a long-term Brazilian-Argentinian collaboration for the study of GC systems in early-type galaxies. In the context of this collaboration, we obtained deep NIR photometric data in two different bands (J and Ks), which were later combined with high quality optical Gemini + GMOS photometry previously obtained by the Argentinian team. This allowed us to obtain different color indices, less sensitive to the effect of horizontal branch (HB) stars for several hundreds of GC candidates, and to make an initial assessment of the presence or absence of multiple GC populations in colors in NGC1395.Instituto de Astrofísica de La PlataMuseo de Astronomía y Geofísic

The Brazil-Argentina gemini group for the study of globular cluster systems (BAGGs GCs): Flamingos-2 and GMOS data for NGC 1395

In this letter, we present preliminary results of the analysis of Flamingos-2 and GMOS-S photometry of the globular cluster (GC) system of the elliptical galaxy NGC1395. This is the first step of a long-term Brazilian-Argentinian collaboration for the study of GC systems in early-type galaxies. In the context of this collaboration, we obtained deep NIR photometric data in two different bands (J and Ks), which were later combined with high quality optical Gemini + GMOS photometry previously obtained by the Argentinian team. This allowed us to obtain different color indices, less sensitive to the effect of horizontal branch (HB) stars for several hundreds of GC candidates, and to make an initial assessment of the presence or absence of multiple GC populations in colors in NGC1395.Instituto de Astrofísica de La PlataMuseo de Astronomía y Geofísic

Sensor noise in LISA Pathfinder: in-flight performance of the optical test mass readout

We report on the first subpicometer interferometer flown in space. It was part of ESA’s Laser Interferometer Space Antenna (LISA) Pathfinder mission and performed the fundamental measurement of the positional and angular motion of two free-falling test masses. The interferometer worked immediately, stably, and reliably from switch on until the end of the mission with exceptionally low residual noise of 32.0 + 2.4 - 1.7 ¿ ¿ fm / v Hz , significantly better than required. We present an upper limit for the sensor performance at millihertz frequencies and a model for the measured sensitivity above 200 mHz.Peer ReviewedPostprint (published version

Multi-Modal Data Collection for Measuring Health, Behavior, and Living Environment of Large-Scale Participant Cohorts: Conceptual Framework and Findings from Deployments

As mobile technologies become ever more sensor-rich, portable, and ubiquitous, data captured by smart devices are lending rich insights into users' daily lives with unprecedented comprehensiveness, unobtrusiveness, and ecological validity. A number of human-subject studies have been conducted in the past decade to examine the use of mobile sensing to uncover individual behavioral patterns and health outcomes. While understanding health and behavior is the focus for most of these studies, we find that minimal attention has been placed on measuring personal environments, especially together with other human-centric data modalities. Moreover, the participant cohort size in most existing studies falls well below a few hundred, leaving questions open about the reliability of findings on the relations between mobile sensing signals and human outcomes. To address these limitations, we developed a home environment sensor kit for continuous indoor air quality tracking and deployed it in conjunction with established mobile sensing and experience sampling techniques in a cohort study of up to 1584 student participants per data type for 3 weeks at a major research university in the United States. In this paper, we begin by proposing a conceptual framework that systematically organizes human-centric data modalities by their temporal coverage and spatial freedom. Then we report our study design and procedure, technologies and methods deployed, descriptive statistics of the collected data, and results from our extensive exploratory analyses. Our novel data, conceptual development, and analytical findings provide important guidance for data collection and hypothesis generation in future human-centric sensing studies.This work was supported by Whole Communities—Whole Health, a research grand challenge at the University of Texas at Austin, and National Science Foundation Award SES-1758835.Office of the VP for Researc

Charging of free-falling test masses in orbit due to cosmic rays: results from LISA Pathfinder

A comprehensive summary of the measurements made to characterize test-mass charging due to the space environment during the LISA Pathfinder mission is presented. Measurements of the residual charge of the test mass after release by the grabbing and positioning mechanism show that the initial charge of the test masses was negative after all releases, leaving the test mass with a potential in the range from - 12 to - 512 . Variations in the neutral test-mass charging rate between 21.7 and 30.7 ¿ ¿ e ¿ s - 1 were observed over the course of the 17-month science operations produced by cosmic ray flux changes including a Forbush decrease associated with a small solar energetic particle event. A dependence of the cosmic ray charging rate on the test-mass potential between - 30.2 and - 40.3 ¿ ¿ e ¿ s - 1 ¿ V - 1 was observed resulting in an equilibrium test-mass potential between 670 and 960 mV, and this is attributed to a contribution to charging from low-energy electrons emitted from the gold surfaces of the gravitational reference sensor. Data from the onboard particle detector show a reliable correlation with the charging rate and with other environmental monitors of the cosmic ray flux. This correlation is exploited to extrapolate test-mass charging rates to a 20-year period giving useful insight into the expected range of charging rate that may be observed in the LISA mission.Peer ReviewedPostprint (published version

Transient acceleration events in LISA Pathfinder data: properties and possible physical origin

We present an in depth analysis of the transient events, or glitches, detected at a rate of about one per day in the differential acceleration data of LISA Pathfinder. We show that these glitches fall in two rather distinct categories: fast transients in the interferometric motion readout on one side, and true force transient events on the other. The former are fast and rare in ordinary conditions. The second may last from seconds to hours and constitute the majority of the glitches. We present an analysis of the physical and statistical properties of both categories, including a cross-analysis with other time series like magnetic fields, temperature, and other dynamical variables. Based on these analyses we discuss the possible sources of the force glitches and identify the most likely, among which the outgassing environment surrounding the test-masses stands out. We discuss the impact of these findings on the LISA design and operation, and some risk mitigation measures, including experimental studies that may be conducted on the ground, aimed at clarifying some of the questions left open by our analysis.Peer ReviewedPostprint (author's final draft

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

The Brazil-Argentina gemini group for the study of globular cluster systems (BAGGs GCs): Flamingos-2 and GMOS data for NGC 1395

In this letter, we present preliminary results of the analysis of Flamingos-2 and GMOS-S photometry of the globular cluster (GC) system of the elliptical galaxy NGC1395. This is the first step of a long-term Brazilian-Argentinian collaboration for the study of GC systems in early-type galaxies. In the context of this collaboration, we obtained deep NIR photometric data in two different bands (J and Ks), which were later combined with high quality optical Gemini + GMOS photometry previously obtained by the Argentinian team. This allowed us to obtain different color indices, less sensitive to the effect of horizontal branch (HB) stars for several hundreds of GC candidates, and to make an initial assessment of the presence or absence of multiple GC populations in colors in NGC1395.Instituto de Astrofísica de La PlataMuseo de Astronomía y Geofísic