Mon.Not.Roy.Astron.Soc.363:857-866,2005 We report the discovery of 5 massive Wolf-Rayet (WR) stars resulting from a
programme of follow-up spectroscopy of candidate emission line stars in the
...AAO/UKST Southern Galactic Plane H-alpha survey. The 6195-6775 angstrom spectra
of the stars are presented and discussed. A WC9 class is assigned to all 5
stars through comparison of their spectra with those of known late-type WC
stars, bringing the known total number of Galactic WC9 stars to 44. Whilst
three of the five WC9 stars exhibit near infrared (NIR) excesses characteristic
of hot dust emission -- as seen in the great majority of known WC9 stars -- we
find that two of the stars show no discernible evidence of such excesses. This
increases the number of known WC9 stars without NIR excesses to 7. Reddenings
and distances for all 5 stars are estimated.
Accurate emission line fluxes from planetary nebulae (PNe) provide important constraints on the nature of the final phases of stellar evolution. Large, evolved PNe may trace the latest stages of PN ...evolution, where material from the AGB wind is returned to the interstellar medium. However, the low surface brightness and spatially extended emission of large PNe have made accurate measurements of line fluxes difficult with traditional long-slit spectroscopic techniques. Furthermore, distinguishing these nebulae from HII regions, supernova remnants, or interstellar gas ionized by a hot, evolved stellar core can be challenging. Here, we report on an ongoing survey of large Galactic PNe (r > 5') with the Wisconsin H-Alpha Mapper (WHAM), a Fabry-Perot spectrograph designed to detect faint diffuse optical emission lines with high sensitivity and spectral resolution. Our sample includes newly revealed H-alpha enhancements from the AAO/UKST and WHAM H-alpha surveys of Parker et al. and Haffner et al. We present accurate emission line fluxes of H-alpha, NII, and OIII, and compare our data to other measurements. We use the emission line ratios and kinematics of the ionized gas to assess, or in some cases reassess, the identification of some nebulae.
The Isaac Newton Telescope Photometric H-alpha Survey (IPHAS) is currently
mapping the Northern Galactic plane reaching to r'=20 mag with typically 1"
resolution. Hundreds of Planetary Nebulae (PNe), ...both point-like and resolved,
are expected to be discovered. We report on the discovery of the first new PN
from this survey: it is an unusual object located at a large galactocentric
distance and has a very low oxygen abundance. The nebula shows an intricate
morphology: there is an inner ring surrounding the central star, bright inner
lobes with an enhanced waist, and very faint lobular extensions reaching up to
more than 100". We classify it as a quadrupolar PN, a rather unusual class of
planetary showing two pairs of misaligned lobes. From long-slit spectroscopy we
derive TeNII =12800+-1000K, Ne = 390+-40 cm-3, and chemical abundances
typical of Peimbert's Type I nebulae (He/H =0.13, N/O =1.8) with an oxygen
abundance of 12 + log(O/H)=8.17+-0.15. A kinematic distance of 7.0 kpc is
derived, implying an unusually large size of >4 pc for the nebula. The
photometry of the central star indicates the presence of a relatively cool
companion. This, and the evidence for a dense circumstellar disk and
quadrupolar morphology, all of which are rare among PNe, support the hypothesis
that this morphology is related to binary interaction.
We estimate the flux weighted acceleration on the Local Group (LG) from the
near-infrared Two Micron All Sky Redshift Survey (2MRS). The near-infrared flux
weighted dipoles are very robust because ...they closely approximate a mass
weighted dipole, bypassing the effects of redshift distortions and require no
preferred reference frame. We use this method with the redshift information to
determine the change in dipole with distance. The LG dipole seemingly converges
by 60 Mpc/h. Assuming convergence, the comparison of the 2MRS flux dipole and
the CMB dipole provides a value for the combination of the mass density and
luminosity bias parameters Omega_m^0.6/b_L= 0.40+/-0.09.
We have investigated the redshift space distortions in the optically selected
Durham/UKST Galaxy Redshift Survey using the 2-point galaxy correlation
function perpendicular and parallel to the ...observer's line of sight. We present
results for the real space 2-point correlation function, by inverting the
optimally estimated projected correlation function and find good agreement with
other real space estimates. On small, non-linear scales we observe an
elongation of the z-space corelation function contours in the line of sight
direction. Our result for the 1-D pairwise rms velocity dispersion is sigma =
416 +- 36 kms^-1 which is consistent with those from recent redshift surveys
and canonical values, but inconsistent with SCDM or LCDM models. On larger,
linear scales we observe a compression of the z-space correlation function
contours in the line of sight direction. This is due to the infall of galaxies
into overdense regions and the Durham/UKST data favours a value of Omega^0.6/b
= 0.5, where Omega is the mean mass density of the Universe and b is the linear
bias factor which relates the galaxy and mass distributions. Comparison with
other optical estimates yield consistent results, with the conclusion that the
data does not favour an unbiased critical-density universe.
We have investigated the statistical clustering properties of galaxies by
calculating the 2-point galaxy correlation function from the Durham/UKST Galaxy
Redshift Survey. This survey is magnitude ...limited to bj = 17, contains 2500
galaxies sampled at a rate of one in three and surveys a 4 \times 10^6
(h^-1Mpc)^3 volume of space. We have empirically determined the optimal method
of estimating the 2-point correlation function from just such a magnitude
limited survey. Using this method, our correlation function results confirm the
previously claimed detections of large scale power out to 40h^-1 Mpc scales. We
compare with two common models of cosmological structure formation and find
that our 2-point correlation function has power significantly in excess of the
standard cold dark matter model in the 10-30h^-1 Mpc region, supporting the
observational results of the APM galaxy survey.
We present the results for the galaxy luminosity function as estimated from
the Durham/UKST Galaxy Redshift Survey. This survey is magnitude limited to bj
= 17, contains 2500 galaxies sampled at a ...rate of one in three and surveys a 4
x 10^6 Mpc^3 volume of space. The maximum likelihood parameters for a standard
Schechter luminosity function are estimated to be M*bj = -19.72+-0.09, alpha =
-1.14+-0.08 and phi* = (1.2 +- 0.2) x 10^-2 ( h^3Mpc^-3). A comparison with
galaxy luminosity functions from other redshift surveys shows good agreement
and the shape of the luminosity function now appears well-defined down to Mbj =
-17. There are some discrepancies between the different surveys for galaxies
fainter than this absolute magnitude. However, our estimate agrees well with
that from the APM-Stromlo Galaxy Redshift Survey and we measure a fairly flat
faint end slope.
The Parkes-MIT-NRAO (PMN) radio survey has been used to generate a quasi all-sky study of Galactic Supernova Remnants (SNRs) at a common frequency of 4.85 GHz. We present flux densities estimated for ...the sample of 110 Southern Galactic SNRs (up to Dec = - 65 deg.) observed with the Parkes 64-m radio telescope and an additional sample of 54 from the Northern PMN (up to Dec = +64 deg.) survey undertaken with the Green Bank 43-m (20 SNRs) and 91-m (34 SNRs) radio telescopes. Out of this total sample of 164 selected SNRs (representing 71% of the 231 known SNRs in the Green catalogue) we consider 138 to provide reliable estimates of flux density and surface brightness distribution. This sub-sample represents those SNRs which fall within carefully chosen selection criteria which minimises the effects of the known problems in establishing reliable fluxes from the PMN survey data. Our selection criteria are based on a judicious restriction of source angular size and telescope beam together with careful evaluation of fluxes on a case by case basis. This gives confidence in the newly derived PMN fluxes when the selection criteria are respected. We find a sharp drop off in the flux densities for Galactic SNRs beyond 4 Jy and then a fairly flat distribution from 5-9 Jy, a slight decline and a further flat distribution from 9-20 Jy though the numbers of SNR in each Jy bin are low. We also re-visit the contentious Sigma-D relation to determine a new power law index for a sub-sample of shell type SNRs which yields beta= -2.2 +/- 0.6. This new evaluation of the Sigma-D relation, applied to the restricted sample, provides new distance estimates and their Galactic scale height distribution. We find a peak in the SNR distribution between 7-11 kpc with most restricted to +/- 100 pc Galactic scale height.
MNRAS 1996, 283, 367 A significant empty region was found between the southern Pavo- Indus (PI)
wall and the northern Perseus-Pisces (PP) chain. This survey tests the reality
of this void which may ...simply reflect previous poor sampling of the galaxies in
this region. Redshifts for a magnitude selected sample of 379 galaxies were
obtained covering the four UKST/SERC survey fields with Bt <= 17.0. All
redshifts were obtained with the FLAIR multi-object spectroscopy system on the
1.2 m U.K. Schmidt Telescope at Siding Spring, Australia. Two highly
significant density enhancements were found in the galaxy distribution at 133
Mpc and 200 Mpc (Ho=75 km/s/Mpc). We claim that no connexion exists between PP
and PI. However, a southern extension of PP was detected and makes the total
length of this chain of more than 150 Mpc.
PDF