5,512 research outputs found
Present and future of the OTELO project
OTELO is an emission-line object survey carried out with the red tunable
filter of the instrument OSIRIS at the GTC, whose aim is to become the deepest
emission-line object survey to date. With 100% of the data of the first
pointing finally obtained in June 2014, we present here some aspects of the
processing of the data and the very first results of the OTELO survey. We also
explain the next steps to be followed in the near future.Comment: Oral contribution presented in the XI Scientific Meeting of the
Spanish Astronomical Society held on September 8-12, in Teruel, Spain (7
pages, 2 figures, 1 table). To appear in Highlights of Spanish Astrophysics
VIII, Proceedings of the XI Scientific Meeting of the Spanish Astronomical
Society. Eds. A. J. Cenarro, F. Figueras, C. Hern\'andez-Monteagudo, J.
Trujillo, L. Valdiviels
Census of HII regions in NGC 6754 derived with MUSE: Constraints on the metal mixing scale
We present a study of the HII regions in the galaxy NGC 6754 from a two
pointing mosaic comprising 197,637 individual spectra, using Integral Field
Spectrocopy (IFS) recently acquired with the MUSE instrument during its Science
Verification program. The data cover the entire galaxy out to ~2 effective
radii (re ), sampling its morphological structures with unprecedented spatial
resolution for a wide-field IFU. A complete census of the H ii regions limited
by the atmospheric seeing conditions was derived, comprising 396 individual
ionized sources. This is one of the largest and most complete catalogue of H ii
regions with spectroscopic information in a single galaxy. We use this
catalogue to derive the radial abundance gradient in this SBb galaxy, finding a
negative gradient with a slope consistent with the characteristic value for
disk galaxies recently reported. The large number of H ii regions allow us to
estimate the typical mixing scale-length (rmix ~0.4 re ), which sets strong
constraints on the proposed mechanisms for metal mixing in disk galaxies, like
radial movements associated with bars and spiral arms, when comparing with
simulations. We found evidence for an azimuthal variation of the oxygen
abundance, that may be related with the radial migration. These results
illustrate the unique capabilities of MUSE for the study of the enrichment
mechanisms in Local Universe galaxies.Comment: 13 pages, 7 Figurs, accepted for publishing in A&
Dielectric susceptibility of the Coulomb-glass
We derive a microscopic expression for the dielectric susceptibility
of a Coulomb glass, which corresponds to the definition used in classical
electrodynamics, the derivative of the polarization with respect to the
electric field. The fluctuation-dissipation theorem tells us that is a
function of the thermal fluctuations of the dipole moment of the system. We
calculate numerically for three-dimensional Coulomb glasses as a
function of temperature and frequency
The Poor Survival among Pulmonary Tuberculosis Patients in Chiapas, Mexico: The Case of Los Altos Region
Objective. To analyse survival in patients with pulmonary tuberculosis (PTB) and factors associated with such survival. Design. Study of a cohort of patients aged over 14 years diagnosed with PTB from January 1, 1998 to July 31, 2005. During 2004–2006 a home visit was made to each patient and, during 2008-2009, they were visited again. During these visits a follow-up interview was administered; when the patient had died, a verbal autopsy was conducted with family members. Statistical analysis consisted of survival tests, Kaplan-Meier log-rank test and Cox regression. Results. Of 305 studied patients, 68 had died due to PTB by the time of the first evaluation, 237 were followed-up for a second evaluation, and 10 of them had died of PTB. According to the Cox regression, age (over 45 years) and treatment duration (under six months) were associated with a poorer survival. When treatment duration was excluded, the association between poorer survival with age persisted, whereas with having been treated via DOTS strategy, was barely significant. Conclusions. In the studied area it is necessary that patients receive a complete treatment scheme, and to give priority to patients aged over 45 years
OTELO survey: optimal emission-line flux determination with OSIRIS/GTC
Emission-line galaxies are important targets for understanding the chemical
evolution of galaxies in the universe. Deep, narrow-band imaging surveys allow
to detect and study the flux and the equivalent widths (EW) of the emission
line studied. The present work has been developed within the context of the
OTELO project, an emission line survey using the Tunable Filters (TF) of
OSIRIS, the first generation instrument on the GTC 10.4m telescope located in
La Palma, Spain, that will observe through selected atmospheric windows
relatively free of sky emission lines. With a total survey area of 0.1 square
degrees distributed in different fields, reaching a 5 \sigma depth of 10^-18
erg/cm^2/s and detecting objects of EW < 0.3 A, OTELO will be the deepest
emission line survey to date. As part of the OTELO preparatory activities, the
objective of this study is to determine the best combination of sampling and
full width at half maximum (FWHM) for the OSIRIS tunable filters for deblending
H\alpha from [NII] lines by analyzing the flux errors obtained. We simulated
the OTELO data by convolving a complete set of synthetic HII galaxies in EW
with different widths of the OSIRIS TFs. We estimated relative flux errors of
the recovered H\alpha and [NII]6583 lines. We found that, for the red TF, a
FWHM of 12 A and a sampling of 5 A is an optimal combination that allow
deblending H\alpha from the [NII]6583 line with a flux error lower than 20%.
This combination will allow estimating SFRs and metallicities using the H\alpha
flux and the N2 method, respectively.Comment: 16 pages, 9 figures. Some authors added. Accepted for publication in
PAS
FIR-detected Lyman break galaxies at z ~ 3: Dust attenuation and dust correction factors at high redshift
Lyman break galaxies (LBGs) represent one of the kinds of star-forming
galaxies that are found in the high-redshift universe. The detection of LBGs in
the FIR domain can provide very important clues on their dust attenuation and
total SFR, allowing a more detailed study than those performed so far. In this
work we explore the FIR emission of a sample of 16 LBGs at z ~ 3 in the
GOODS-North and GOODS-South fields that are individually detected in PACS-100um
or PACS-160um. These detections demonstrate the possibility of measuring the
dust emission of LBGs at high redshift. We find that PACS-detected LBGs at z ~
3 are highly obscured galaxies which belong to the Ultra luminous IR galaxies
or Hyper luminous IR galaxies class. Their total SFR cannot be recovered with
the dust attenuation factors obtained from their UV continuum slope or their
SED-derived dust attenuation employing Bruzual & Charlot (2003) templates. Both
methods underestimate the results for most of the galaxies. Comparing with a
sample of PACS-detected LBGs at z ~ 1 we find evidences that the FIR emission
of LBGs might have changed with redshift in the sense that the dustiest LBGs
found at z ~ 3 have more prominent FIR emission, are dustier for a given UV
slope, and have higher SFR for a given stellar mass than the dustiest LBGs
found at z ~ 1.Comment: Accepted for publication in A&A letter
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