1,995 research outputs found
A Database of Cepheid Distance Moduli and TRGB, GCLF, PNLF and SBF Data Useful for Distance Determinations
We present a compilation of Cepheid distance moduli and data for four
secondary distance indicators that employ stars in the old stellar populations:
the planetary nebula luminosity function (PNLF), the globular cluster
luminosity function (GCLF), the tip of the red giant branch (TRGB), and the
surface brightness fluctuation (SBF) method. The database includes all data
published as of July 15, 1999. The main strength of this compilation resides in
all data being on a consistent and homogeneous system: all Cepheid distances
are derived using the same calibration of the period-luminosity relation, the
treatment of errors is consistent for all indicators, measurements which are
not considered reliable are excluded. As such, the database is ideal for
inter-comparing any of the distance indicators considered, or for deriving a
Cepheid calibration to any secondary distance indicator. Specifically, the
database includes: 1) Cepheid distances, extinctions and metallicities; 2)
apparent magnitudes of the PNLF cutoff; 3) apparent magnitudes and colors of
the turnover of the GCLF (both in the V- and B-bands); 4) apparent magnitudes
of the TRGB (in the I-band) and V-I colors at and 0.5 magnitudes fainter than
the TRGB; 5) apparent surface brightness fluctuation magnitudes I, K', K_short,
and using the F814W filter with the HST/WFPC2. In addition, for every galaxy in
the database we give reddening estimates from DIRBE/IRAS as well as HI maps,
J2000 coordinates, Hubble and T-type morphological classification, apparent
total magnitude in B, and systemic velocity. (Abridged)Comment: Accepted for publication in the Astrophysical Journal Supplement
Series. Because of space limitations, the figures included are low resolution
bitmap images. Original figures can be found at
http://www.astro.ucla.edu/~laura/pub.ht
The HST Key Project on the Extragalactic Distance Scale. XXII. The Discovery of Cepheids in NGC 1326-A
We report on the detection of Cepheids and the first distance measurement to
the spiral galaxy NGC 1326-A, a member of the Fornax cluster of galaxies. We
have employed data obtained with the Wide Field and Planetary Camera 2 on board
the Hubble Space Telescope. Over a 49 day interval, a total of twelve V-band
(F555W) and eight I-band (F814W) epochs of observation were obtained. Two
photometric reduction packages, ALLFRAME and DoPHOT, have been employed to
obtain photometry measures from the three Wide Field CCDs. Variability analysis
yields a total of 17 Cepheids in common with both photometry datasets, with
periods ranging between 10 and 50 days. Of these 14 Cepheids with high-quality
lightcurves are used to fit the V and I period-luminosity relations and derive
apparent distance moduli, assuming a Large Magellanic Cloud distance modulus
(m-M) (LMC) = 18.50 +- 0.10 mag and color excess E(B-V) = 0.10 mag. Assuming
A(V)/E(V-I) = 2.45, the DoPHOT data yield a true distance modulus to NGC 1326-A
of (m-M)_0 = 31.36 +- 0.17 (random) +- 0.13 (systematic) mag, corresponding to
a distance of 18.7 \pm 1.5 (random) \pm 1.2 (systematic) Mpc. The derived
distance to NGC 1326-A is in good agreement with the distance derived
previously to NGC 1365, another spiral galaxy member of the Fornax cluster.
However the distances to both galaxies are significantly lower than to NGC
1425, a third Cepheid calibrator in the outer parts of the cluster.Comment: 33 pages A gzipped tar file containing 12 figures can be obtained
from http://www.ipac.caltech.edu/H0kp/n1326a/n1326a.htm
The HST Key Project on the Extragalactic Distance Scale XXV. A Recalibration of Cepheid Distances to Type Ia Supernovae and the Value of the Hubble Constant
Cepheid-based distances to seven Type Ia supernovae (SNe)-host galaxies have
been derived using the standard HST Key Project on the Extragalactic Distance
Scale pipeline. For the first time, this allows for a transparent comparison of
data accumulated as part of three different HST projects, the Key Project, the
Sandage et al. Type Ia SNe program, and the Tanvir et al. Leo I Group study.
Re-analyzing the Tanvir et al. galaxy and six Sandage et al. galaxies we find a
mean (weighted) offset in true distance moduli of 0.12+/-0.07 mag -- i.e., 6%
in linear distance -- in the sense of reducing the distance scale, or
increasing H0. Adopting the reddening-corrected Hubble relations of Suntzeff et
al. (1999), tied to a zero point based upon SNe~1990N, 1981B, 1998bu, 1989B,
1972E and 1960F and the photometric calibration of Hill et al. (1998), leads to
a Hubble constant of H0=68+/-2(random)+/-5(systematic) km/s/Mpc. Adopting the
Kennicutt et al. (1998) Cepheid period-luminosity-metallicity dependency
decreases the inferred H0 by 4%. The H0 result from Type Ia SNe is now in good
agreement, to within their respective uncertainties, with that from the
Tully-Fisher and surface brightness fluctuation relations.Comment: Accepted for publication in The Astrophysical Journal. 62 pages,
LaTeX, 9 Postscript figures. Also available at
http://casa.colorado.edu/~bgibson/publications.htm
The HST Key Project on the Extragalactic Distance Scale XXVI. The Calibration of Population II Secondary Distance Indicators and the Value of the Hubble Constant
A Cepheid-based calibration is derived for four distance indicators that
utilize stars in the old stellar populations: the tip of the red giant branch
(TRGB), the planetary nebula luminosity function (PNLF), the globular cluster
luminosity function (GCLF) and the surface brightness fluctuation method (SBF).
The calibration is largely based on the Cepheid distances to 18 spiral galaxies
within cz =1500 km/s obtained as part of the HST Key Project on the
Extragalactic Distance Scale, but relies also on Cepheid distances from
separate HST and ground-based efforts. The newly derived calibration of the SBF
method is applied to obtain distances to four Abell clusters in the velocity
range between 3800 and 5000 km/s, observed by Lauer et al. (1998) using the
HST/WFPC2. Combined with cluster velocities corrected for a cosmological flow
model, these distances imply a value of the Hubble constant of H0 = 69 +/- 4
(random) +/- 6 (systematic) km/s/Mpc. This result assumes that the Cepheid PL
relation is independent of the metallicity of the variable stars; adopting a
metallicity correction as in Kennicutt et al. (1998), would produce a (5 +/-
3)% decrease in H0. Finally, the newly derived calibration allows us to
investigate systematics in the Cepheid, PNLF, SBF, GCLF and TRGB distance
scales.Comment: Accepted for publication in the Astrophysical Journal. 48 pages
(including 13 figures and 4 tables), plus two additional tables in landscape
format. Also available at http://astro.caltech.edu/~lff/pub.htm K' SBF
magnitudes have been update
The HST Key Project on the Extragalactic Distance Scale. XXVIII. Combining the Constraints on the Hubble Constant
Since the launch of the Hubble Space Telescope nine years ago, Cepheid
distances to 25 galaxies have been determined for the purpose of calibrating
secondary distance indicators. A variety of these can now be calibrated, and
the accompanying papers by Sakai, Kelson, Ferrarese, and Gibson employ the full
set of 25 galaxies to consider the Tully-Fisher relation, the fundamental plane
of elliptical galaxies, Type Ia supernovae, and surface brightness
fluctuations.
When calibrated with Cepheid distances, each of these methods yields a
measurement of the Hubble constant and a corresponding measurement uncertainty.
We combine these measurements in this paper, together with a model of the
velocity field, to yield the best available estimate of the value of H_0 within
the range of these secondary distance indicators and its uncertainty.
The result is H_0 = 71 +/- 6 km/sec/Mpc. The largest contributor to the
uncertainty of this 67% confidence level result is the distance of the Large
Magellanic Cloud, which has been assumed to be 50 +/- 3 kpc
The HST Key Project on the Extragalactic Distance Scale XVII. The Cepheid Distance to NGC 4725
The distance to NGC 4725 has been derived from Cepheid variables, as part of
the Hubble Space Telescope Key Project on the Extragalactic Distance Scale.
Thirteen F555W (V) and four F814W (I) epochs of cosmic-ray-split Wide Field and
Planetary Camera 2 observations were obtained. Twenty Cepheids were discovered,
with periods ranging from 12 to 49 days. Adopting a Large Magellanic Cloud
distance modulus and extinction of 18.50+/-0.10 mag and E(V-I)=0.13 mag,
respectively, a true reddening-corrected distance modulus (based on an analysis
employing the ALLFRAME software package) of 30.50 +/- 0.16 (random) +/- 0.17
(systematic) mag was determined for NGC 4725. The corresponding of distance of
12.6 +/- 1.0 (random) +/- 1.0 (systematic) Mpc is in excellent agreement with
that found with an independent analysis based upon the DoPHOT photometry
package. With a foreground reddening of only E(V-I)=0.02, the inferred
intrinsic reddening of this field in NGC 4725, E(V-I)=0.19, makes it one of the
most highly-reddened, encountered by the HST Key Project, to date.Comment: To be published in The Astrophysical Journal, Vol. 512 (1999). 34
pages, LaTeX, 9 jpg figure
The Hubble Space Telescope Extragalactic Distance Scale Key Project XXIII. The Discovery of Cepheids In NGC 3319
The distance to NGC 3319 has been determined from Cepheid variable stars as
part of the Hubble Space Telescope Key Project on the Extragalactic Distance
Scale. Thirteen and four epochs of observations, using filters F555W (V) and
F814W (I) respectively, were made with the Wide Field Planetary Camera 2.
Thirty-three Cepheid variables between periods of 8 and 47 days were
discovered. Adopting a Large Magellanic Cloud distance modulus of 18.50 +- 0.10
mag and extinction of E(V-I)=0.13 mag, a true reddening-corrected distance
modulus (based on an analysis employing the ALLFRAME software package) of 30.78
+- 0.14 (random) +- 0.10 (systematic) mag and the extinction of E(V-I) = 0.06
mag were determined for NGC 3319. This galaxy is the last galaxy observed for
the HST H0 Key Project.Comment: 22 pages. A gzipped tar file containing 16 figures can be obtained
from http://www.ipac.caltech.edu/H0kp/n3319/n3319.htm
Rapid Field Immunoassay for Detecting Antibody to Sin Nombre Virus in Deer Mice
We developed a 1-hour field enzyme immunoassay (EIA) for detecting antibody to Sin Nombre virus in deer mice (Peromyscus maniculatus). The assay specificity and sensitivity were comparable to those of a standard EIA. This test will permit identification of rodents with antibody to this and perhaps other hantaviruses
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