Publications (2)0 Total impact
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Guillermo A. Blanc,
Tim Weinzirl,
Mimi Song,
Amanda Heiderman,
Karl Gebhardt,
Shardha Jogee,
Neal J. Evans II,
Remco C. E. van den Bosch,
Rongxin Luo,
Niv Drory,
Maximilian Fabricius,
David Fisher,
Lei Hao, Kyle Kaplan,
Irina Marinova,
Nalin Vutisalchavakul,
Peter Yoachim
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ABSTRACT: We present the survey design, data reduction, and spectral fitting pipeline
for the VIRUS-P Exploration of Nearby Galaxies (VENGA). VENGA is an integral
field spectroscopic survey, which maps the disks of 30 nearby spiral galaxies.
Targets span a wide range in Hubble type, star formation activity, morphology,
and inclination. The VENGA data-cubes have 5.6'' FWHM spatial resolution, ~5A
FWHM spectral resolution, sample the 3600A-6800A range, and cover large areas
typically sampling galaxies out to ~0.7 R_25. These data-cubes can be used to
produce 2D maps of the star formation rate, dust extinction, electron density,
stellar population parameters, the kinematics and chemical abundances of both
stars and ionized gas, and other physical quantities derived from the fitting
of the stellar spectrum and the measurement of nebular emission lines. To
exemplify our methods and the quality of the data, we present the VENGA
data-cube on the face-on Sc galaxy NGC 628 (a.k.a. M 74). The VENGA
observations of NGC 628 are described, as well as the construction of the
data-cube, our spectral fitting method, and the fitting of the stellar and
ionized gas velocity fields. We also propose a new method to measure the
inclination of nearly face-on systems based on the matching of the stellar and
gas rotation curves using asymmetric drift corrections. VENGA will measure
relevant physical parameters across different environments within these
galaxies, allowing a series of studies on star formation, structure assembly,
stellar populations, chemical evolution, galactic feedback, nuclear activity,
and the properties of the interstellar medium in massive disk galaxies.
03/2013;
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ABSTRACT: BL Lacertae (Lac) objects that are detected at very-high energies (VHE) are
of fundamental importance to study multiple astrophysical processes, including
the physics of jets, the properties of the extragalactic background light and
the strength of the intergalactic magnetic field. Unfortunately, since most
blazars have featureless optical spectra that preclude a redshift
determination, a substantial fraction of these VHE extragalactic sources cannot
be used for cosmological studies. To assess whether molecular lines are a
viable way to establish distances, we have undertaken a pilot program at the
IRAM 30m telescope to search for CO lines in three BL Lac objects with known
redshifts. We report a positive detection of M_H2 ~ 3x10^8 Msun toward 1ES
1959+650, but due to the poor quality of the baseline, this value is affected
by a large systematic uncertainty. For the remaining two sources, W Comae and
RGB J0710+591, we derive 3sigma upper limits at, respectively, M_H2 < 8.0x10^8
Msun and M_H2 < 1.6x10^9 Msun, assuming a line width of 150 km/s and a standard
conversion factor alpha=4 M_sun/(K km/s pc^2). If these low molecular gas
masses are typical for blazars, blind redshift searches in molecular lines are
currently unfeasible. However, deep observations are still a promising way to
obtain precise redshifts for sources whose approximate distances are known via
indirect methods. Our observations further reveal a deficiency of molecular gas
in BL Lac objects compared to quasars, suggesting that the host galaxies of
these two types of active galactic nuclei (AGN) are not drawn from the same
parent population. Future observations are needed to assess whether this
discrepancy is statistically significant, but our pilot program shows how
studies of the interstellar medium in AGN can provide key information to
explore the connection between the active nuclei and the host galaxies.
05/2012;
