The ACS Fornax Cluster Survey VII. Half-Light Radii of Globular Clusters in Early-Type Galaxies

We measure the half-light radii of globular clusters (GCs) in 43 galaxies from the ACS Fornax Cluster Survey (ACSFCS). We use these data to extend previous work in which the environmental dependencies of the half-light radii of GCs in early type galaxies in the ACS Virgo Cluster Survey (ACSVCS) were studied, and a corrected mean half-light radius (corrected for the observed environmental trends) was suggested as a reliable distance indicator. This work both increases the sample size for the study of the environmental dependencies, and adds leverage to the study of the corrected half-light radius as a possible distance indicator (since Fornax lies at a larger distance than the Virgo cluster). We study the environmental dependencies of the size of GCs using both a Principal Component Analysis as well as 2D scaling relations. We largely confirm the environmental dependencies shown in Jordan et al. (2005), but find evidence that there is a residual correlation in the mean half-light radius of GC systems with galaxy magnitude, and subtle differences in the other correlations - so there may not be a universal correction for the half-light radii of lower luminosity galaxy GC systems. The main factor determining the size of a GC in an early type galaxy is the GC color. Red GCs have = 2.8+/-0.3 pc, while blue GCs have = 3.4+/-0.3 pc. We show that for bright early-type galaxies (M_B < -19 mag), the uncorrected mean half-light radius of the GC system is by itself an excellent distance indicator (with error ~11%), having the potential to reach cosmologically interesting distances in the era of high angular resolution adaptive optics on large optical telescopes.Comment: ApJ in press, 19 pages, 16 figures

The ACS Fornax Cluster Survey. IX. The Color-Magnitude Relation of Globular Cluster Systems

We investigate the color-magnitude relation for globular clusters (GCs) -- the so-called "blue tilt" -- detected in the ACS Fornax Cluster Survey and using the combined sample of GCs from the ACS Fornax and Virgo Cluster Surveys. We find a tilt of gamma_z=d(g-z)/dz=-0.0257 +- 0.0050 for the full GC sample of the Fornax Cluster Survey (~5800 GCs). This is slightly shallower than the value gamma_z=-0.0459 +- 0.0048 found for the Virgo Cluster Survey GC sample (~11100 GCs). The slope for the merged Fornax and Virgo datasets (~16900 GCs) is gamma_z=-0.0293 +- 0.0085, corresponding to a mass-metallicity relation of Z ~ M^0.43. We find that the blue tilt sets in at GC masses in excess of M ~ 2*10^5 M_sun. The tilt is stronger for GCs belonging to high-mass galaxies (M_* > 5 * 10^10 M_sun) than for those in low-mass galaxies (M_* < 5 * 10^10 M_sun). It is also more pronounced for GCs with smaller galactocentric distances. Our findings suggest a range of mass-metallicity relations Z_GC ~ M_GC^(0.3-0.7) which vary as a function of host galaxy mass/luminosity. We compare our observations to a recent model of star cluster self-enrichment with generally favorable results. We suggest that, within the context of this model, the proto-cluster clouds out of which the GCs formed may have had density profiles slightly steeper than isothermal and/or star formation efficiencies somewhat below 0.3. We caution, however, that the significantly different appearance of the CMDs defined by the GC systems associated with galaxies of similar mass and morphological type pose a challenge to any single mechanism that seeks to explain the blue tilt. We therefore suggest that the merger/accretion histories of individual galaxies have played a non-negligible role determining the distribution of GCs in the CMDs of individual GC systems

Discovery of a New Member of the Inner Oort Cloud from The Next Generation Virgo Cluster Survey

We report the discovery of 2010 GB$_{174}$, a likely new member of the Inner Oort Cloud (IOC). 2010 GB$_{174}$ is one of 91 Trans Neptunian Objects (TNOs) and Centaurs discovered in a 76 deg$^2$ contiguous region imaged as part of the Next Generation Virgo Cluster Survey (NGVS) --- a moderate ecliptic latitude survey reaching a mean limiting magnitude of $g^\prime \simeq 25.5$ --- using MegaPrime on the 3.6m Canada France Hawaii Telescope. 2010 GB$_{174}$ is found to have an orbit with semi-major axis $a\simeq350.8$ AU, inclination $i \simeq 21.6^\circ$ and pericentre $q\sim48.5$ AU. This is the second largest perihelion distance among known solar system objects. Based on the sky coverage and depth of the NGVS, we estimate the number of IOC members with sizes larger than 300 km ($H_V \le 6.2$ mag) to be $\simeq 11\,000$. A comparison of the detection rate from the NGVS and the PDSSS (a characterized survey that `re-discovered' the IOC object Sedna) gives, for an assumed a power-law LF for IOC objects, a slope of $\alpha \simeq 0.7 \pm 0.2$, with only two detections in this region this slope estimate is highly uncertain.Comment: 20 pages, 3 figures, 1 table. Accepted for publication in The Astrophysical Journal Letter

Load Generators for Automatic Simulation of Urban Fleets

[EN] To ensure cities sustainability, we must deal with, among other challenges, traffic congestion, and its associated carbon emissions. We can approach such a problem from two perspectives: the transition to electric vehicles, which implies the need for charging station infrastructure, and the optimization of traffic flow. However, cities are complex systems, so it is helpful to test changes on them in controlled environments like the ones provided by simulators. In our work, we use SimFleet, an agent-based fleet simulator. Nevertheless, SimFleet does not provide tools for easily setting up big experiments, neither to simulate the realistic movement of its agents inside a city. Aiming to solve that, we enhanced SimFleet introducing two fully configurable generators that automatize the creation of experiments. First, the charging stations generator, which allocates a given amount of charging stations following a certain distribution, enabling to simulate how transports would charge and compare distributions. Second, the load generator, which populates the experiment with a given number of agents of a given type, introducing them dynamically in the simulation, and assigns them a movement that can be either random or based on real city data. The generators proved to be useful for comparing different distributions of charging stations as well as different agent behaviors over the same complex setup.This work was partially supported by MINECO/FEDER RTI2018-095390-B-C31 project of the Spanish government. Pasqual Martí and Jaume Jordán are funded by UPV PAID-06-18 project. Jaume Jordán is also funded by grant APOSTD/2018/010 of Generalitat Valenciana - Fondo Social Europeo.Martí Gimeno, P.; Jordán, J.; Palanca Cámara, J.; Julian Inglada, VJ. (2020). Load Generators for Automatic Simulation of Urban Fleets. Springer. 394-405. https://doi.org/10.1007/978-3-030-51999-5_33S394405Campo, C.: Directory facilitator and service discovery agent. FIPA Document Repository (2002)Dong, J., Liu, C., Lin, Z.: Charging infrastructure planning for promoting battery electric vehicles: an activity-based approach using multiday travel data. Transp. Res. Part C: Emerg. Technol. 38, 44–55 (2014)Jordán, J., Palanca, J., Del Val, E., Julian, V., Botti, V.: A multi-agent system for the dynamic emplacement of electric vehicle charging stations. Appl. Sci. 8(2), 313 (2018)Noori, H.: Realistic urban traffic simulation as vehicular Ad-hoc network (VANET) via Veins framework. In: 2012 12th Conference of Open Innovations Association (FRUCT), pp. 1–7. IEEE (2012)Palanca, J., Terrasa, A., Carrascosa, C., Julián, V.: SimFleet: a new transport fleet simulator based on MAS. In: De La Prieta, F., et al. (eds.) PAAMS 2019. CCIS, vol. 1047, pp. 257–264. Springer, Cham (2019). https://doi.org/10.1007/978-3-030-24299-2_22Skippon, S., Garwood, M.: Responses to battery electric vehicles: UK consumer attitudes and attributions of symbolic meaning following direct experience to reduce psychological distance. Transp. Res. Part D: Transp. Environ. 16(7), 525–531 (2011)del Val, E., Palanca, J., Rebollo, M.: U-tool: a urban-toolkit for enhancing city maps through citizens’ activity. In: Demazeau, Y., Ito, T., Bajo, J., Escalona, M.J. (eds.) PAAMS 2016. LNCS (LNAI), vol. 9662, pp. 243–246. Springer, Cham (2016). https://doi.org/10.1007/978-3-319-39324-7_2