754 research outputs found
Individual Stellar Halos of Massive Galaxies Measured to 100 kpc at 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 . 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 : Rest-Frame UV Spectra
We report initial results for spectroscopic observations of candidates of
Lyman Break Galaxies (LBGs) at 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 mag, including one AGN, are
confirmed to be at . 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 1260, OI+SiII 1303, and CII 1334 (mean
rest-frame equivalent widths of them are \AA). These
properties are significantly different from those of the mean rest-frame UV
spectrum of LBGs at , but are quite similar to those of subgroups of
LBGs at 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 are chemically evolved to some degree and
have a dusty environment. Since the fraction of such LBGs at in our
sample is larger than that at , we may witness some sign of evolution
of LBGs from to , 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 ) among LBGs at . More observations are required to
establish spectroscopic nature of LBGs at .Comment: 16 pages, 3 figures, accepted by Ap
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