206 research outputs found
Conservation systematics of the shield-backed trapdoor spiders of the nigrum-group (Mygalomorphae, idiopidae, idiosoma): Integrative taxonomy reveals a diverse and threatened fauna from south-western Australia [dataset]
Supplementary material from: Rix MG, Huey JA, Cooper SJB, Austin AD, Harvey MS (2018) Conservation systematics of the shield-backed trapdoor spiders of the nigrum-group (Mygalomorphae, Idiopidae, Idiosoma): integrative taxonomy reveals a diverse and threatened fauna from south-western Australia. ZooKeys 756: 1-121. https://doi.org/10.3897/zookeys.756.24397
Supplementary material 1: Atlas of morphology : Explanation note: Atlas of morphology for shield-backed trapdoor spiders of the Idiosoma nigrum-group, illustrating a representative selection of male specimens for each species, in five standard views.
Supplementary material 2: GenBank data : Explanation note: Spreadsheet of specimens sequenced for the molecular analyses, with associated collection data and GenBank accession numbers.
Supplementary material 3: COI dataset : Explanation note: Nexus file of the aligned COI dataset for 82 taxa.
Supplementary material 4: FULL dataset : Explanation note: Nexus file of the aligned FULL dataset for 82 taxa.
Supplementary material 5: COI p-distances : Explanation note: Spreadsheet with matrix of COI p-distances for 61 sequenced specimens of Idiosoma in the nigrum-group, along with a summary of mean inter- and intra-specific p-distances
Sagittarius Tidal Debris 90 kpc from the Galactic Center
A new overdensity of A-colored stars in distant parts of the Milky Way's
stellar halo, at a dereddened SDSS magnitude of g_0 = 20.3, is presented.
Identification of associated variable RR Lyrae candidates supports the claim
that these are blue horizontal branch stars. The inferred distance of these
stars from the Galactic center is 90 kpc, assuming the absolute magnitude of
these stars is M_g_0 = 0.7 and that the Sun is 8.5 kpc from the Galactic
center. The new tidal debris is within 10 kpc of same plane as other confirmed
tidal debris from the disruption of the Sagittarius dwarf galaxy, and could be
associated with the trailing tidal arm. Distances to the Sagittarius stream
estimated from M stars are about 13% smaller than our inferred distances. The
tidal debris has a width of at least 10 degrees, and is traced for more than 20
degrees across the sky. The globular cluster NGC 2419 is located within the
detected tidal debris, and may also have once been associated with the
Sagittarius dwarf galaxy.Comment: 4 figures, ApJL in pres
Across the Indian Ocean: a remarkable example of trans-oceanic dispersal in an austral mygalomorph spider [dataset]
The Migidae are a family of austral trapdoor spiders known to show a highly restricted and disjunct distribution pattern. Here, we aim to investigate the phylogeny and historical biogeography of the group, which was previously thought to be vicariant in origin, and examine the biogeographic origins of the genus Moggridgea using a dated multi-gene phylogeny. Moggridgea specimens were sampled from southern Australia and Africa, and Bertmainus was sampled from Western Australia. Sanger sequencing methods were used to generate a robust six marker molecular dataset consisting of the nuclear genes 18S rRNA, 28S rRNA, ITS rRNA, XPNPEP3 and H3 and the mitochondrial gene COI. Bayesian and Maximum Likelihood methods were used to analyse the dataset, and the key dispersal nodes were dated using BEAST. Based on our data, we demonstrate that Moggridgea rainbowi from Kangaroo Island, Australia is a valid member of the otherwise African genus Moggridgea. Molecular clock dating analyses show that the inter-specific divergence of M. rainbowi from African congeners is between 2.27â16.02 million years ago (Mya). This divergence date significantly post-dates the separation of Africa from Gondwana (95 Mya) and therefore does not support a vicariant origin for Australian Moggridgea. It also pre-dates human colonisation of Kangaroo Island, a result which is further supported by the intra-specific divergence date of 1.10â6.39 Mya between separate populations on Kangaroo Island. These analyses provide strong support for the hypothesis that Moggridgea colonised Australia via long-distance trans-Indian Ocean dispersal, representing the first such documented case in a mygalomorph spider
Discovery of Two Gravitationally Lensed Quasars with Image Separations of 3 Arcseconds from the Sloan Digital Sky Survey
We report the discovery of two doubly-imaged quasars, SDSS
J100128.61+502756.9 and SDSS J120629.65+433217.6, at redshifts of 1.838 and
1.789 and with image separations of 2.86'' and 2.90'', respectively. The
objects were selected as lens candidates from the Sloan Digital Sky Survey
(SDSS). Based on the identical nature of the spectra of the two quasars in each
pair and the identification of the lens galaxies, we conclude that the objects
are gravitational lenses. The lenses are complicated; in both systems there are
several galaxies in the fields very close to the quasars, in addition to the
lens galaxies themselves. The lens modeling implies that these nearby galaxies
contribute significantly to the lens potentials. On larger scales, we have
detected an enhancement in the galaxy density near SDSS J100128.61+502756.9.
The number of lenses with image separation of ~3'' in the SDSS already exceeds
the prediction of simple theoretical models based on the standard
Lambda-dominated cosmology and observed velocity function of galaxies.Comment: 24 pages, 9 figures, accepted for publication in Ap
The Rest-Frame Optical Luminosity Density, Color, and Stellar Mass Density of the Universe from z=0 to z=3
We present the evolution of the rest-frame optical luminosity density, of the
integrated rest-frame optical color, and of the stellar mass density for a
sample of Ks-band selected galaxies in the HDF-S. We derived the luminosity
density in the rest-frame U, B, and V-bands and found that the luminosity
density increases by a factor of 1.9+-0.4, 2.9+-0.6, and 4.9+-1.0 in the V, B,
and U rest-frame bands respectively between a redshift of 0.1 and 3.2. We
derived the luminosity weighted mean cosmic (U-B)_rest and (B-V)_rest colors as
a function of redshift. The colors bluen almost monotonically with increasing
redshift; at z=0.1, the (U-B)_rest and (B-V)_rest colors are 0.16 and 0.75
respectively, while at z=2.8 they are -0.39 and 0.29 respectively. We derived
the luminosity weighted mean M/LV using the correlation between (U-V)_rest and
log_{10} M/LV which exists for a range in smooth SFHs and moderate extinctions.
We have shown that the mean of individual M/LV estimates can overpredict the
true value by ~70% while our method overpredicts the true values by only ~35%.
We find that the universe at z~3 had ~10 times lower stellar mass density than
it does today in galaxies with LV>1.4 \times 10^{10} h_{70}^-2 Lsol. 50% of the
stellar mass of the universe was formed by $z~1-1.5. The rate of increase in
the stellar mass density with decreasing redshift is similar to but above that
for independent estimates from the HDF-N, but is slightly less than that
predicted by the integral of the SFR(z) curve.Comment: 19 pages, 12 figures, Accepted for Publication in the Dec. 20, 2003
edition of the Astrophysical Journal. Minor changes made to match the
accepted version including short discussions on the effects of clustering and
on possible systematic effects resulting from photometric redshift error
Kinematic study of the disrupting globular cluster Palomar 5 using VLT spectra
Wide-field photometric data from the Sloan Digital Sky Survey have recently
revealed that the Galactic globular cluster Palomar 5 is in the process of
being tidally disrupted (Odenkirchen et al. 2001). Here we investigate the
kinematics of this sparse remote star cluster using high resolution spectra
from the Very Large Telescope (VLT). Twenty candidate cluster giants located
within 6 arcmin of the cluster center have been observed with the UV-Visual
Echelle Spectrograph (UVES) on VLT-UT2. The spectra provide radial velocities
with a typical accuracy of 0.15 km/s. We find that the sample contains 17
certain cluster members with very coherent kinematics, two unrelated field
dwarfs, and one giant with a deviant velocity, which is most likely a cluster
binary showing fast orbital motion. From the confirmed members we determine the
heliocentric velocity of the cluster as -58.7 +- 0.2 km/s. The total
line-of-sight velocity dispersion of the cluster stars is 1.1 +- 0.2 km/s (all
members) or 0.9 +- 0.2 km/s (stars on the red giant branch only). This is the
lowest velocity dispersion that has so far been measured for a stellar system
classified as a globular cluster. The shape of the velocity distribution
suggests that there is a significant contribution from orbital motions of
binaries and that the dynamical part of the velocity dispersion is therefore
still substantially smaller than the total dispersion. ... (abridged)Comment: 29 pages including 10 figures, accepted for publication in the
Astronomical Journa
The extended tails of Palomar 5: A ten degree arc of globular cluster tidal debris
Using wide-field photometric data from the Sloan Digital Sky Survey (SDSS) we
recently showed that the Galactic globular cluster Palomar 5 is in the process
of being tidally disrupted. Its tidal tails were initially detected in a 2.5
degree wide band along the celestial equator. A new analysis of SDSS data for a
larger field now reveals that the tails of Pal 5 have a much larger spatial
extent and can be traced over an arc of 10 deg across the sky, corresponding to
a projected length of 4 kpc at the distance of the cluster. The number of
former cluster stars found in the tails adds up to about 1.2 times the number
of stars in the cluster. The radial profile of stellar surface density in the
tails follows approximately a power law r^gamma with -1.5 < gamma < -1.2.
The stream of debris from Pal 5 is significantly curved, which demonstrates
its acceleration by the Galactic potential. The cluster is presently near the
apocenter but has repeatedly undergone disk crossings in the inner part of the
Galaxy leading to strong tidal shocks. Our results suggest that the observed
debris originates mostly from mass loss within the last 2 Gyrs. The cluster is
likely to be destroyed after the next disk crossing, which will happen in about
100 Myr. (abridged)Comment: 44 pages, including 14 figures (Figs.1,3 & 14 with decreased
resolution), accepted for publication in the Astronomical Journa
The Sloan Digital Sky Survey Quasar Lens Search. II. Statistical lens sample from the third data release
We report the first results of our systematic search for strongly lensed quasars using the spectroscopically confirmed quasars in the Sloan Digital Sky Survey (SDSS). Among 46,420 quasars from the SDSS Data Release 3 (~4188 deg^2), we select a subsample of 22,683 quasars that are located at redshifts between 0.6 and 2.2 and are brighter than the Galactic extinction-corrected i-band magnitude of 19.1. We identify 220 lens candidates from the quasar subsample, for which we conduct extensive and systematic follow-up observations in optical and near-infrared wavebands, in order to construct a complete lensed quasar sample at image separations between 1" and 20" and flux ratios of faint to bright lensed images larger than 10^(â0.5). We construct a statistical sample of 11 lensed quasars. Ten of these are galaxy-scale lenses with small image separations (~ 1"-2") and one is a large separation (15") system which is produced by a massive cluster of galaxies, representing the first statistical sample of lensed quasars including both galaxy- and cluster-scale lenses. The Data Release 3 spectroscopic quasars contain an additional 11 lensed quasars outside the statistical sample
Evolution of the Ionizing Background and the Epoch of Reionization from the Spectra of z~6 Quasars
We study the process of cosmic reionization and estimate the ionizing
background in the IGM using the Lyman series absorption in the spectra of the
four quasars at 5.7<z<6.3 discovered by the SDSS. We derive the evolution of
the ionizing background at high redshifts, using both semi-analytic techniques
and cosmological simulations to model the density fluctuations in the IGM. The
existence of the complete Ly alpha Gunn-Peterson trough in the spectrum of the
z=6.28 quasar SDSS 1030+0524 indicates a photoionization rate Gamma_{-12} at
z~6 lower than 0.08, at least a factor of 6 smaller than the value at z~3. The
Ly beta and Ly gamma Gunn-Peterson troughs give an even stronger limit
Gamma_{-12}<0.02 due to their smaller oscillator strengths, indicating that the
ionizing background in the IGM at z~6 is more than 20 times lower than that at
z~3. Meanwhile, the volume-averaged neutral hydrogen fraction increases from
10^{-5} at z~3 to >10^{-3} at z~6. At this redshift, the mass-averaged neutral
hydrogen fraction is larger than 1%; the mildly overdense regions (delta > 3)
are still mostly neutral and the comoving mean free path of ionizing photons is
shorter than 8 Mpc. Comparison with simulations of cosmological reionization
shows that the observed properties of the IGM at z~6 are typical of those in
the era at the end of the overlap stage of reionization when the individual HII
regions merge. Thus, z~6 marks the end of the reionization epoch. The redshift
of reionization constrains the small scale power of the mass density
fluctuations and the star forming efficiency of the first generation of
objects.Comment: AJ accepted, 27 pages; minor change
VLT observations of the z=6.28 quasar SDSS 1030+0524
We present new VLT spectroscopic observations of the most distant quasar
known, SDSS J1030+0524 at z=6.28 which was recently discovered by the Sloan
Digital Sky Survey. We confirm the presence of a complete Gunn-Peterson trough
caused by neutral hydrogen in the intergalactic medium. There is no detectable
flux over the wavelength range from 8450 to 8710 A. We set an improved limit on
the drop of the flux level blueward of the Ly alpha line: a factor of
> 200. Below 8450 A the spectrum shows a rise in flux, with a large fraction
(> 60 %) of the total emission produced by few narrow features of transmitted
flux. We discuss the obvious proximity effect around this quasar, with the
presence of transmitted flux with many absorption features in a region of about
23h^{-1} comoving Mpc. If assuming the surrounding medium were completely
neutral, the size of this region would imply a quasar lifetime of \~1.3x10^7
years.
We also present near-IR spectroscopy of both SDSS J1030+0524 and of SDSS
J1306+05, the second most distant quasar known at redshift 6.0. We combine
measurements of the CIV line and limits on the HeII emission with the NV line
measurements from the optical spectra to derive line ratios, and by implication
the abundances of these early quasar environments. The results are
indistinguishable from those of lower redshift quasars and indicate little or
no evolution in the abundances from z ~ 6 to z ~ 2. The line ratios suggest
supersolar metallicities, implying that the first stars around the quasars must
have formed at least a few hundreds of Myrs prior to the observation, i.e. at
redshift higher than 8.Comment: Accepted by the Astronomical Journal (scheduled for May 2002).
Proximity effect section revise
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