162 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
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
AEGIS: Enhancement of Dust-enshrouded Star Formation in Close Galaxy Pairs and Merging Galaxies up to z ~ 1
Using data from the DEEP2 Galaxy Redshift Survey and HST/ACS imaging in the
Extended Groth Strip, we select nearly 100 interacting galaxy systems including
kinematic close pairs and morphologically identified merging galaxies. Spitzer
MIPS 24 micron fluxes of these systems reflect the current dusty star formation
activity, and at a fixed stellar mass (M_{*}) the median infrared luminosity
(L_{IR}) among merging galaxies and close pairs of blue galaxies is twice (1.9
+/- 0.4) that of control pairs drawn from isolated blue galaxies. Enhancement
declines with galaxy separation, being strongest in close pairs and mergers and
weaker in wide pairs compared to the control sample. At z ~ 0.9, 7.1% +/- 4.3%
of massive interacting galaxies (M_{*} > 2*10^{10} M_{solar}) are found to be
ULIRGs, compared to 2.6% +/- 0.7% in the control sample. The large spread of IR
luminosity to stellar mass ratio among interacting galaxies suggests that this
enhancement may depend on the merger stage as well as other as yet unidentified
factors (e.g., galaxy structure, mass ratio, orbital characteristics, presence
of AGN or bar). The contribution of interacting systems to the total IR
luminosity density is moderate (<= 36 %).Comment: 12 pages, 2 figures, 1 table, minor changes to match the proof
version, accepted for publication in the ApJL AEGIS Special Issu
Absolute physical calibration in the infrared
We determine an absolute calibration for the Multiband Imaging Photometer for Spitzer 24 μm band and recommend adjustments to the published calibrations for Two Micron All Sky Survey (2MASS), Infrared Array Camera (IRAC), and IRAS photometry to put them on the same scale. We show that consistent results are obtained by basing the calibration on either an average A0V star spectral energy distribution (SED), or by using the absolutely calibrated SED of the Sun in comparison with solar-type stellar photometry (the solar analog method). After the rejection of a small number of stars with anomalous SEDs (or bad measurements), upper limits of ~1.5% root mean square (rms) are placed on the intrinsic infrared (IR) SED variations in both A-dwarf and solar-type stars. These types of stars are therefore suitable as general-purpose standard stars in the IR. We provide absolutely calibrated SEDs for a standard zero magnitude A star and for the Sun to allow extending this work to any other IR photometric system. They allow the recommended calibration to be applied from 1 to 25 μm with an accuracy of ~2%, and with even higher accuracy at specific wavelengths such as 2.2, 10.6, and 24 μm, near which there are direct measurements. However, we confirm earlier indications that Vega does not behave as a typical A0V star between the visible and the IR, making it problematic as the defining star for photometric systems. The integration of measurements of the Sun with those of solar-type stars also provides an accurate estimate of the solar SED from 1 through 30 μm, which we show agrees with theoretical models
The DEEP2 Galaxy Redshift Survey: Mean Ages and Metallicities of Red Field Galaxies at z ~ 0.9 from Stacked Keck/DEIMOS Spectra
As part of the DEEP2 galaxy redshift survey, we analyze absorption line
strengths in stacked Keck/DEIMOS spectra of red field galaxies with weak to no
emission lines, at redshifts 0.7 <= z <= 1. Comparison with models of stellar
population synthesis shows that red galaxies at z ~ 0.9 have mean
luminosity-weighted ages of the order of only 1 Gyr and at least solar
metallicities. This result cannot be reconciled with a scenario where all stars
evolved passively after forming at very high z. Rather, a significant fraction
of stars can be no more than 1 Gyr old, which means that star formation
continued to at least z ~ 1.2. Furthermore, a comparison of these distant
galaxies with a local SDSS sample, using stellar populations synthesis models,
shows that the drop in the equivalent width of Hdelta from z ~ 0.9 to 0.1 is
less than predicted by passively evolving models. This admits of two
interpretations: either each individual galaxy experiences continuing low-level
star formation, or the red-sequence galaxy population from z ~ 0.9 to 0.1 is
continually being added to by new galaxies with younger stars.Comment: A few typos were corrected and numbers in Table 1 were revise
- …