5 research outputs found
Space Telescope Imaging Spectrograph Parallel Observations of the Planetary Nebula M94-20
The planetary nebula M94--20 in the Large Magellanic Cloud was
serendipitously observed with the Space Telescope Imaging Spectrograph on board
the Hubble Space Telescope as part of the Hubble Space Telescope Archival Pure
Parallel Program. We present spatially resolved imaging and spectral data of
the nebula and compare them with ground based data, including detection of
several emission lines from the nebula and the detection of the central star.
We find the total H alpha + [NII] flux = 7.3e-15 erg s^-1 cm^-2 and we estimate
the magnitude of the central star to be m_V = 26.0 +/- 0.2. Many other H alpha
sources have been found in M31, M33 and NGC 205 as well. We discuss the use of
the parallel observations as a versatile tool for planetary nebula surveys and
for other fields of astronomical research.Comment: Latex, 14 pages, 2 JPEG figures, 2 tables. PASP Research Note, June
1999, in pres
Imaging and spectroscopy of arcs around the most luminous X-ray cluster RX J1347.5-1145
The cluster RX J1347.5-1145, the most luminous cluster in the X-ray
wavelengths, was imaged with the newly installed Space Telescope Imaging
Spectrograph (STIS) on-board HST. Its relatively high redshift (0.451) and
luminosity indicate that this is one of the most massive of all known clusters.
The STIS images unambiguously show several arcs in the cluster. The largest two
arcs (> 5 arcsec in length) are symmetrically situated on opposite sides of the
cluster, at a distance of ~ 35 arcsec from the central galaxy. The STIS images
also show approximately 100 faint galaxies within the radius of the arcs whose
combined luminosity is ~ 4 x 10^11 Lsun. We also present ground-based
spectroscopic observations of the northern arc which show one clear emission
line at 6730 A, which is consistent with an identification as [OII] 3727 A,
implying a redshift of 0.81 for this arc. The southern arc shows a faint
continuum but no emission features. The surface mass within the radius of the
arcs (240 kpc), as derived from the gravitational lensing, is 6.3 x 10^14 Msun.
The resultant mass-to-light ratio of ~1200 is higher than what is seen in many
clusters but smaller than the value recently derived for some `dark' X-ray
clusters (Hattori et al. 1997). The total surface mass derived from the X-ray
flux within the radius of the arcs is ~2.1 - 6.8 x 10^14 Msun, which implies
that the ratio of the gravitational to the X-ray mass is ~1 to 3. The surface
GAS mass within this radius is ~3.5 x 10^13 Msun, which implies that at least
6% of the total mass within this region is baryonic.Comment: 3 figures. Replaced with the final version as appears in the
Astrophysical Journal Letters (Jan 10, 1998 issue). This incorporates some
important revision
Bad Astronomy
This web site is devoted to airing out myths and common misconceptions about astronomy and related topics. There is also a blog which the author, who is an astronomer, often posts to