173 research outputs found
The Absolute Magnitude of the Sun in Several Filters
This paper presents a table with estimates of the absolute magnitude of the
Sun and the conversions from to the AB and ST systems for several
wide-band filters used in ground and space-based observatories. These estimates
use the dustless spectral energy distribution (SED) of Vega, calibrated
absolutely using the SED of Sirius, to set the zero-points and a
composite spectrum of the Sun that coadds space-based observations from the
ultra-violet to the near infrared with models of the Solar atmosphere. The
uncertainty of the absolute magnitudes is estimated comparing the synthetic
colors with photometric measurements of solar analogs and is found to be
0.02 magnitudes. Combined with the uncertainty of 2% in the calibration
of the Vega SED, the errors of these absolute magnitudes are 3--4%.
Using these SEDs, for the three of the most utilized filters in extragalactic
work the estimated absolute magnitudes of the Sun are = 5.44, =
4.81 and = 3.27 mag in the system and = 5.31, =
4.80 and = 5.08 mag in AB.Comment: 17 pages, 2 figures, accepted by ApJS. Composite solar spectrum
available for download at http://mips.as.arizona.edu/~cnaw/sun.htm
Effects of the Environment on the Properties of Seyfert Galaxies
We identify 175 Seyfert galaxies from the Southern Sky Redshift Survey -
SSRS2. We use the entire SSRS2 catalog to investigate the correlation between
the presence of AGN with host environment. The AGN phenomenon is more strongly
correlated with the internal host properties, than with the external
environment. In particular, we find that Seyferts reside in more luminous
galaxies, and are twice as frequent in barred galaxies and systems showing sign
of advanced merger condition, when compared to a control sample.Comment: 4 pages, 3 figs, 1 tables, to appear in the proceedings of "The
Interplay among Black Holes, Stars and ISM in Galactic Nuclei", IAU 222, eds.
T. Storchi Bergmann, L.C. Ho, and H.R. Schmit
Mid-Infrared Selected Quasars I: Virial Black Hole Mass and Eddington Ratios
We provide a catalog of 391 mid-infrared-selected (MIR, 24m)
broad-emission-line (BEL, type 1) quasars in the 22 deg SWIRE Lockman Hole
field. This quasar sample is selected in the MIR from Spitzer MIPS with Jy, jointly with an optical magnitude limit of r (AB) 22.5 for
broad line identification. The catalog is based on MMT and SDSS spectroscopy to
select BEL quasars, extends the SDSS coverage to fainter magnitudes and lower
redshifts, and recovers a more complete quasar population. The MIR-selected
quasar sample peaks at 1.4, and recovers a significant and constant
(20\%) fraction of extended objects with SDSS photometry across magnitudes,
which was not included in the SDSS quasar survey dominated by point sources.
This sample also recovers a significant population of . We then investigate the continuum luminosity and line profiles of these
MIR quasars, and estimate their virial black hole masses and the Eddington
ratios. The SMBH mass shows evidence of downsizing, though the Eddington ratios
remain constant at . Compared to point sources in the same redshift
range, extended sources at show systematically lower Eddington ratios.
The catalog and spectra are publicly available online.Comment: 72 pages, 27 figures, 16 tables; ApJ accepte
Properties of host galaxies of submillimeter sources as revealed by JWST Early Release Observations in SMACS J0723.3-7327
Using the 0.9--4.4~m imaging data from the James Webb Space Telescope
(JWST) Early Release Observation in the SMACS J0723.3-7327 galaxy cluster
field, we discuss the properties of three submillimeter galaxies (SMGs)
detected by the Atacama Large Millimeter Array. These sources are magnified by
1.4--2.1due to gravitational lensing. This is the first time that SMG
host galaxies are resolved in the rest-frame near-infrared (NIR). One source
was previous undetected by HST, while the remaining two are disk galaxies with
S\'ersic indices of and star formation rates on or just below the
star formation "main sequence". Their submillimeter emission originates from
the inner parts of the hosts, suggesting that their dust contents are
concentrated towards the center. The host half-light radii measured in the
rest-frame NIR are 1.5 smaller than those measured in the
rest-frame optical, consistent with a concentrated dust distribution. The more
severe extinction that optical light suffers towards the center makes it
seemingly less concentrated. Therefore, we expect that the optically-based
determination of the stellar mass distribution within host galaxies could still
be severely biased by dust. Interestingly, these two disk galaxies are
dramatically different in their outer regions, with one being star forming and
the other being quiescent. Upcoming JWST observations of statistically
significant samples of SMGs will allow us to understand the correlation between
the dusty star forming regions and their hosts.Comment: 11 pages, 7 figures, accepted by ApJ
A Quantitative Evaluation of the Galaxy Component of COSMOS and APM Catalogs
We have carried out an independent quantitative evaluation of the galaxy
component of the "COSMOS/UKST Southern Sky Object Catalogue" (SSC) and the
"APM/UKST J Catalogue" (APM). Using CCD observations our results corroborate
the accuracy of the photometry of both catalogs, which have an overall
dispersion of about 0.2 mag in the range 17 <= b_J <= 21.5. The SSC presents
externally calibrated galaxy magnitudes that follow a linear relation, while
the APM instrumental magnitudes of galaxies, only internally calibrated by the
use of stellar profiles, require second-order corrections. The completeness of
both catalogs in a general field falls rapidly fainter than b_J = 20.0, being
slightly better for APM. The 90% completeness level of the SSC is reached
between b_J = 19.5 and 20.0, while for APM this happens between b_J = 20.5 and
21.0. Both SSC and APM are found to be less complete in a galaxy cluster field.
Galaxies misclassified as stars in the SSC receive an incorrect magnitude
because the stellar ones take saturation into account besides using a different
calibration curve. In both cases, the misclassified galaxies show a large
diversity of colors that range from typical colors of early-types to those of
blue star-forming galaxies. A possible explanation for this effect is that it
results from the combination of low sampling resolutions with properties of the
image classifier for objects with characteristic sizes close to the
instrumental resolution. We find that the overall contamination by stars
misclassified as galaxies is < 5% to b_J = 20.5, as originally estimated for
both catalogs. Although our results come from small areas of the sky, they are
extracted from two different plates and are based on the comparison with two
independent datasets.Comment: 14 pages of text and tables, 8 figures; to be published in the
Astronomical Journal; for a single postscript version file see
ftp://danw.on.br/outgoing/caretta/caretta.p
The COS Absorption Survey of Baryon Harbors (CASBaH): Warm-hot Circumgalactic Gas Reservoirs Traced by Ne VIII Absorption
We survey the highly ionized circumgalactic media (CGM) of 29 blindly
selected galaxies at 0.49 < z_(gal) < 1.44 based on high-S/N ultraviolet
spectra of z > 1 QSOs and the galaxy database from the COS Absorption Survey of
Baryon Harbors (CASBaH). We detect the Ne VIII doublet in nine of the galaxies,
and for gas with N(Ne VIII) > 10^13.3 cm^-2 (> 10^13.5 cm^-2), we derive a Ne
VIII covering fraction f_c = 75 +15/-25% (44 +22/-20%) within impact parameter
(rho) < 200 kpc of M_* = 10^(9.5-11.5) Msol galaxies and f_c = 70 +16/-22% (f_c
= 42 +20/-17%) within rho < 1.5 virial radii. We estimate the mass in Ne
VIII-traced gas to be M_gas(Ne VIII) > 10^9.5 Msol (Z/Zsol)^-1, or 6-20% of the
expected baryonic mass if the Ne VIII absorbers have solar metallicity.
Ionizing Ne VII to Ne VIII requires 207 eV, and photons with this energy are
scarce in the CGM. However, for the median halo mass and redshift of our
sample, the virial temperature is close to the peak temperature for the Ne VIII
ion, and the Ne VIII-bearing gas is plausibly collisionally ionized near this
temperature. Moreover, we find that photoionized Ne VIII requires cool and
low-density clouds that would be highly underpressured (by approximately two
orders of magnitude) relative to the putative, ambient virialized medium,
complicating scenarios where such clouds could survive. Thus, more complex
(e.g., non-equilibrium) models may be required; this first statistical sample
of Ne VIII absorber/galaxy systems will provide stringent constraints for
future CGM studies.Comment: Published in ApJL, Volume 877, Issue 2, Article L2
The Seyfert Population in the Local Universe
The magnitude-limited catalog of the Southern Sky Redshift Survey (SSRS2), is
used to characterize the properties of galaxies hosting Active Galactic Nuclei.
Using emission-line ratios, we identify a total of 162 (3%) Seyfert galaxies
out of the parent sample with 5399 galaxies. The sample contains 121 Seyfert 2
galaxies and 41 Seyfert 1. The SSRS2 Seyfert galaxies are predominantly in
spirals of types Sb and earlier, or in galaxies with perturbed appearance as
the result of strong interactions or mergers. Seyfert galaxies in this sample
are twice as common in barred hosts than the non-Seyferts. By assigning
galaxies to groups using a percolation algorithm we find that the Seyfert
galaxies in the SSRS2 are more likely to be found in binary systems, when
compared to galaxies in the SSRS2 parent sample. However, there is no
statistically significant difference between the Seyfert and SSRS2 parent
sample when systems with more than 2 galaxies are considered. The analysis of
the present sample suggests that there is a stronger correlation between the
presence of the AGN phenomenon with internal properties of galaxies
(morphology, presence of bar, luminosity) than with environmental effects
(local galaxy density, group velocity dispersion, nearest neighbor distance).Comment: 35 pages, 13 figures, Accepted to be publised in Astronomical Journa
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