Individual Stellar Halos of Massive Galaxies Measured to 100 kpc at 0.3<z<0.50.3<z<0.5 using Hyper Suprime-Cam

Massive galaxies display extended light profiles that can reach several hundreds of kilo parsecs. These stellar halos provide a fossil record of galaxy assembly histories. Using data that is both wide (~100 square degree) and deep (i>28.5 mag/arcsec^2 in i-band), we present a systematic study of the stellar halos of a sample of more than 3000 galaxies at 0.3 < z < 0.5 with $\log M_{\star}/M_{\odot} > 11.4$. Our study is based on high-quality (0.6 arcsec seeing) imaging data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP), which enables us to individually estimate surface mass density profiles to 100 kpc without stacking. As in previous work, we find that more massive galaxies exhibit more extended outer profiles. When this extended light is not properly accounted for as a result of shallow imaging or inadequate profile modeling, the derived stellar mass function can be significantly underestimated at the highest masses. Across our sample, the ellipticity of outer light profiles increases substantially as we probe larger radii. We show for the first time that these ellipticity gradients steepen dramatically as a function of galaxy mass, but we detect no mass-dependence in outer color gradients. Our results support the two-phase formation scenario for massive galaxies in which outer envelopes are built up at late times from a series of merging events. We provide surface mass surface mass density profiles in a convenient tabulated format to facilitate comparisons with predictions from numerical simulations of galaxy formation.Comment: Submitted to MNRAS; 23 pages, 8 figures, 2 appendix; Data will be made available here: http://massivegalaxies.com/ once the paper is publishe

La educación ambiental en las instituciones educativas del municipio de Villa Hayes para la reducción de la generación de residuos sólidos urbanos

La presente investigación describe y analiza las representaciones sociales de la Educación Ambiental desde la perspectiva de la Gestión Integral de Residuos Sólidos Urbanos en tres Instituciones Educativas, correspondientes a la Educación Escolar Básica y a la Educación Media del Sistema Educativo Nacional del Municipio de Villa Hayes. Con base en el análisis proponen estrategias de Educación Ambiental orientadas a la reducción de la generación de Residuos Sólidos Urbanos. Se ha utilizado una investigación con enfoque cualitativo, además del tipo exploratorio y descriptivo. Como instrumento de recolección de datos, se han aplicado las técnicas de entrevistas personales semiestructuradas basado en un cuestionario a los estudiantes, docentes y personal de limpieza de las Instituciones Educativas seleccionadas y al Jefe de Planificación de la Municipalidad, además, de una revisión documental con los directores de las Instituciones. Se pudo verificar que la Educación Ambiental, desde la perspectiva de la Gestión Integral de Residuos Sólidos Urbanos, está muy limitada al conocimiento y la iniciativa de los docentes. De modo similar, se pudo constatar la importancia que le dan los estudiantes a las actividades de Educación Ambiental que les inculcan los docentes. Por otra parte, se logró identificar que los docentes tienen altos niveles de actitudes ambientales, pero existe una necesidad de fortalecer la competencia en la sostenibilidad ambiental. Por lo tanto, mejorar la misma es vital para evitar barreras en el momento de formular y transmitir los conocimientos a los estudiantes. Finalmente, se observó la necesidad de ajustar sus acciones con base en los problemas ambientales del territorio y que permita a los estudiantes formar parte de la problemática, que los motiven y desarrollen sus capacidades ambientales.CONACYT - Consejo Nacional de Ciencia y TecnologíaPROCIENCI

What Kinds of Volunteers become more motivated by Community Currency?

Local communities in Japan are struggling to increase the number of participants in volunteer activities in order to revitalize local life. To maintain the enthusiasm of active volunteers and entice new volunteers, a new type of reward to increase motivation is needed. Accordingly, community currencies (hereafter, CCs) have been introduced as a reward in an attempt to provide such a source of motivation. In particular, local residents have been expected to participate in volunteer work more frequently in return for receiving CCs; however, there is no evidence yet as to whether CCs arouse their motivation to do volunteer work. In this study, we investigated whether CCs play a role in raising local residents’ motivation to do volunteer work. Our conclusion is that even some people with a no-reward orientation are likely to have their motivation raised by CCs, rather than diminished. This result shows that their perception towards CCs and cash is dramatically different though CCs have the same monetary value as cash

Lyman Break Galaxies at z∼5z\sim5: Rest-Frame UV Spectra

We report initial results for spectroscopic observations of candidates of Lyman Break Galaxies (LBGs) at $z\sim5$ in a region centered on the Hubble Deep Field-North by using the Faint Object Camera and Spectrograph attached to the Subaru Telescope. Eight objects with $I_C\leq25.0$ mag, including one AGN, are confirmed to be at $4.5<z<5.2$. The rest-frame UV spectra of seven LBGs commonly show no or weak Lyalpha emission line (rest-frame equivalent width of 0-10\AA) and relatively strong low-ionization interstellar metal absorption lines of SiII $\lambda$1260, OI+SiII $\lambda$1303, and CII $\lambda$1334 (mean rest-frame equivalent widths of them are $-1.2 \sim -5.1$\AA). These properties are significantly different from those of the mean rest-frame UV spectrum of LBGs at $z\sim3$, but are quite similar to those of subgroups of LBGs at $z\sim3$ with no or weak Lyalpha emission. The weakness of Lyalpha emission and strong low-ionization interstellar metal absorption lines may indicate that these LBGs at $z\sim5$ are chemically evolved to some degree and have a dusty environment. Since the fraction of such LBGs at $z\sim5$ in our sample is larger than that at $z\sim3$, we may witness some sign of evolution of LBGs from $z\sim5$ to $z\sim3$, though the present sample size is very small. It is also possible, however, that the brighter LBGs tend to show no or weak Lyalpha emission, because our spectroscopic sample is bright (brighter than $L^{\ast}$) among LBGs at $z\sim5$. More observations are required to establish spectroscopic nature of LBGs at $z\sim5$.Comment: 16 pages, 3 figures, accepted by Ap