REPORT ON WHT/ISIS OBSERVING
RUN 22/5/96 -- 23/5/96

Observers : M. Merrifield, K. Kuijken, S. Gottesman

REPORT ON WHT/ISIS OBSERVING RUN 22/5/96 -- 23/5/96

Observers: M. Merrifield, K. Kuijken, S. Gottesman


SUMMARY

Apart from minor technical and weather problems, the run went well.
We obtained spectra of NGC3359, NGC4314, NGC4596, NGC5383, NGC5850, and
NGC6951.  In each case we observed the bar major axis, but we also
obtained a number of other slit positions for several of the galaxies
where there was a clear physical motivation for doing so.  Details are
given below.


WEATHER

The first night of the run was clear, and pretty much photometric.
The second night was plagued by cirrus, which had significant impact
on the sky brightness before the moon set; it clouded over entirely
for the last hour of the run.  Seeing was pretty miserable both nights
(between 2 and 4 arcseconds), but fortunately the large-scale
kinematics should not be too badly affected by poor seeing.


TECHNICAL PROBLEMS

The spectrograph behaved itself very well throughout the run.  The
only significant problem was with the telescope pointing, which was
affected by a blown light bulb in the azimuthal encoder.  Tracking down
and circumventing this problem lost us the first hour of the first
night.


OBSERVING STRATEGY

Spectrograph set-up:

We observed using both arms of ISIS, with a 1200 line grating in each
arm.  The red arm spectral coverage was centred 8600A to cover the Ca
triplet, and the blue arm was centered on 5090A to cover the Mg b
feature at 5170A, and to fill a gap in the already-obtained IDS
spectra.  Velocity resolution with this set-up is around 14 km/s/pixel
on the red arm, and 24 km/s/pixel on the blue arm.  The spectrograph
was focused so that an unresolved line in a comparison lamp projected
to around 2 pixels on the red arm and 2.5 pixels on the blue arm
(through a 1.25 arcsecond slit).


Integration times:

We tried to obtain at least 3600 sec on the bar major axis of each
target galaxy.  Integration times on other slit positions were
adjusted to provide sufficient S/N for the intended analysis (see
below).


Calibration frames:

All long exposures were bracketed by Cu-Ne-Ar lamp exposures for
wavelength calbration.

We also obtained dome flats and internal (tungsten lamp) flats to
calibrate pixel-to-pixel variations in the chip, and spectra of the
twilight sky to measure the vignetting pattern of the telescope and
spectrograph across the slit


Standard stars:

On the first night which was close to photometric, we obtained spectra
for a couple of flux standards (BD28 4211, Feige 110) to allow approximate
flux calibration (although this calibration is not important for
kinematic work).  The second night was non-photometric, so no flux
standards were observed.

During the course of both nights, we also observed 10 radial velocity
standard stars with a range of spectral types (late F to late K) for
kinematic analysis.


NOTES ON INDIVIDUAL TARGETS

Night 1:

NGC 4596: This SB0 galaxy is ideally suited for studying stellar
kinematics, and is well-oriented for the Tremaine-Weinberg (T-W) and
Canzian methods for pattern speed determination.  We therefore
observed its bar major axis (2400 sec); a slit aligned parallel to the
disk major axis, but offset by 38" to the NE to cut through the end of
the bar (3600 sec); a similar observation offset to the SW (3600 sec);
and the disk minor axis 3600 sec).  The two offset observations can
be used for the T-W analysis, while the minor axis can be used for the
Canzian analysis.

NGC 5383: This intermediate-type barred galaxy can be used to compare
gas and stellar kinematics.  We observed the bar major axis (4800
sec); and disk minor axis (4800 sec).  The Canzian analysis can be
applied to the latter.

NGC 6951: The only target available at the end of the night.  The bar
is rather faint in this system.  We observed its major axis (6000
sec).


Night 2:

NGC 3359: Bar major axis (3600 sec).

NGC 4314: System apears round on the sky at large radii, so probably
close to face-on.  Thus, a good candidate for measuring the
z-dispersion of a bar.  We therefore observed the bar major axis (3600
sec); and a cut offset by 4" NE, parallel to the bar (3600 sec).  The
latter observation follows the "edge" of the bar, so we will be able
to see if the z-dispersion falls or rises away from the major axis.
Any predictions?

NGC 4340: Bar major axis (3600 sec).

NGC 5850: Bar major axis (3600 sec, but through some cloud)

NGC 6951: Bar major axis (1400 sec, before the clouds really closed in).

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