82 research outputs found
A Federal Litigation Program: For Students, Inmates And The Legal Profession
Across the country, efforts have been made by the federal judiciary, the American Bar Association, and law schools to improve the quality of advocacy in the federal courts
A Cepheid Distance to NGC 4603 in Centaurus
In an attempt to use Cepheid variables to determine the distance to the
Centaurus cluster, we have obtained images of NGC 4603 with the Hubble Space
Telescope on 9 epochs using WFPC2 and the F555W and F814W filters. This galaxy
has been suggested to lie within the ``Cen30'' portion of the cluster and is
the most distant object for which this method has been attempted. Previous
distance estimates for Cen30 have varied significantly and some have presented
disagreements with the peculiar velocity predicted from redshift surveys,
motivating this investigation. Using our observations, we have found 61
candidate Cepheid variable stars; however, a significant fraction of these
candidates are likely to be nonvariable stars whose magnitude measurement
errors happen to fit a Cepheid light curve of significant amplitude for some
choice of period and phase. Through a maximum likelihood technique, we
determine that we have observed 43 +/- 7 real Cepheids and that NGC 4603 has a
distance modulus of 32.61 +0.11/-0.10 (random, 1 sigma) +0.24/-0.25
(systematic, adding in quadrature), corresponding to a distance of 33.3 Mpc.
This is consistent with a number of recent estimates of the distance to NGC
4603 or Cen30 and implies a small peculiar velocity consistent with predictions
from the IRAS 1.2 Jy redshift survey if the galaxy lies in the foreground of
the cluster.Comment: Accepted for publication in the Astrophysical Journal. 17 pages with
17 embedded figures and 3 tables using emulateapj.sty. Additional figures and
images may be obtained from http://astro.berkeley.edu/~marc/n4603
The HST Key Project on the Extragalactic Distance Scale. XV. A Cepheid Distance to the Fornax Cluster and Its Implications
Using the Hubble Space Telescope (HST) 37 long-period Cepheid variables have
been discovered in the Fornax Cluster spiral galaxy NGC 1365. The resulting V
and I period-luminosity relations yield a true distance modulus of 31.35 +/-
0.07 mag, which corresponds to a distance of 18.6 +/- 0.6 Mpc. This measurement
provides several routes for estimating the Hubble Constant. (1) Assuming this
distance for the Fornax Cluster as a whole yields a local Hubble Constant of 70
+/-18_{random} [+/-7]_{systematic} km/s/Mpc. (2) Nine Cepheid-based distances
to groups of galaxies out to and including the Fornax and Virgo clusters yield
Ho = 73 (+/-16)_r [+/-7]_s km/s/Mpc. (3) Recalibrating the I-band Tully-Fisher
relation using NGC 1365 and six nearby spiral galaxies, and applying it to 15
galaxy clusters out to 100 Mpc gives Ho = 76 (+/-3)_r [+/-8]_s km/s/Mpc. (4)
Using a broad-based set of differential cluster distance moduli ranging from
Fornax to Abell 2147 gives Ho = 72 (+/-)_r [+/-6]_s km/s/Mpc. And finally, (5)
Assuming the NGC 1365 distance for the two additional Type Ia supernovae in
Fornax and adding them to the SnIa calibration (correcting for light curve
shape) gives Ho = 67 (+/-6)_r [+/-7]_s km/s/Mpc out to a distance in excess of
500 Mpc. All five of these Ho determinations agree to within their statistical
errors. The resulting estimate of the Hubble Constant combining all these
determinations is Ho = 72 (+/-5)_r [+/-12]_s km/s/Mpc.Comment: Accepted for publication in the Astrophysical Journal, Apr. 10 issue
28 pages, 3 tables, 12 figures (Correct figures and abstract
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
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. X. The Cepheid Distance to NGC 7331
The distance to NGC 7331 has been derived from Cepheid variables observed
with HST/WFPC2, as part of the Extragalactic Distance Scale Key Project.
Multi-epoch exposures in F555W (V) and F814W (I), with photometry derived
independently from DoPHOT and DAOPHOT/ALLFRAME programs, were used to detect a
total of 13 reliable Cepheids, with periods between 11 and 42 days. The
relative distance moduli between NGC 7331 and the LMC, imply an extinction to
NGC 7331 of A_V = 0.47+-0.15 mag, and an extinction-corrected distance modulus
to NGC 7331 of 30.89+-0.14(random) mag, equivalent to a distance of 15.1 Mpc.
There are additional systematic uncertainties in the distance modulus of +-0.12
mag due to the calibration of the Cepheid Period-Luminosity relation, and a
systematic offset of +0.05+-0.04 mag if we applied the metallicity correction
inferred from the M101 results of Kennicutt et al 1998.Comment: To be published in The Astrophysical Journal, 1998 July 1, v501 note:
Figs 1 and 2 (JPEG files) and Fig 7 (multipage .eps file) need to be
viewed/printed separatel
The HST Key Project on the Extragalactic Distance Scale XIV. The Cepheids in NGC 1365
We report the detection of Cepheid variable stars in the barred spiral galaxy
NGC 1365, located in the Fornax cluster, using the Hubble Space Telescope Wide
Field and Planetary Camera 2. Twelve V (F555W) and four I (F814W) epochs of
observation were obtained. The two photometry packages, ALLFRAME and DoPHOT,
were separately used to obtain profile-fitting photometry of all the stars in
the HST field. The search for Cepheid variable stars resulted in a sample of 52
variables, with periods between 14 and 60 days, in common with both datasets.
ALLFRAME photometry and light curves of the Cepheids are presented. A subset of
34 Cepheids were selected on the basis of period, light curve shape, similar
ALLFRAME and DoPHOT periods, color, and relative crowding, to fit the Cepheid
period-luminosity relations in V and I for both ALLFRAME and DoPHOT. The
measured distance modulus to NGC 1365 from the ALLFRAME photometry is 31.31 +/-
0.20 (random) +/- 0.18 (systematic) mag, corresponding to a distance of 18.3
+/- 1.7 (random) +/- 1.6 (systematic) Mpc. The reddening is measured to be
E(V-I) = 0.16 +/- 0.08 mag. These values are in excellent agreement with those
obtained using the DoPHOT photometry, namely a distance modulus of 31.26 +/-
0.10 mag, and a reddening of 0.15 +/- 0.10 mag (internal errors only).Comment: 48 pages, 8 tables, 8 figures, to appear in Ap
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