388 research outputs found
Do facial first impressions reflect a shared social reality?
This work was supported by an Australian Research Council (ARC) Discovery Early Career Research Award to CS [DE 190101043], the ARC Centre of Excellence in Cognition and its Disorders [CE110001021], and an ARC Discovery Award [DP170104602]. The funding sources had no influence on the research.Peer reviewedPostprintPostprin
The Metagalactic Ionizing Radiation Field at Low Redshift
We compute the ionizing radiation field at low redshift, arising from
Seyferts, QSOs, and starburst galaxies. This calculation combines recent
Seyfert luminosity functions, extrapolated ultraviolet fluxes from our IUE-AGN
database, and a new intergalactic opacity model based on Hubble Space Telescope
and Keck Ly-alpha absorber surveys. At z = 0 for AGN only, our best estimate
for the specific intensity at 1 Ryd is I_0 = 1.3 (+0.8/-0.5) x 10^-23
ergs/cm^2/s/Hz/sr, independent of H_0, Omega_0, and Lambda. The one-sided
ionizing photon flux is Phi_ion = 3400 (+2100/-1300) photons/cm^2/s, and the H
I photoionization rate is Gamma_HI = 3.2 (+2.0/-1.2) x 10^-14 s^-1 for alpha_s
= 1.8. We also derive Gamma_ HI for z = 0 - 4. These error ranges reflect
uncertainties in the spectral indexes for the ionizing EUV (alpha_s = 1.8 +/-
0.3) and the optical/UV (alpha_UV = 0.86 +/- 0.05), the IGM opacity model, the
range of Seyfert luminosities (0.001 - 100 L*) and the completeness of the
luminosity functions. Our estimate is a factor of three lower than the most
stringent upper limits on the ionizing background (Phi_ion < 10^4
photons/cm^2/s) obtained from H-alpha observations in external clouds, and it
lies within the range implied by other indirect measures. Starburst galaxies
with a sufficiently large Lyman continuum escape fraction, f_ esc > 0.05, may
provide a comparable background to AGN, I_0 (z=0) = 1.1 (+1.5/-0.7) x 10^{-23).
An additional component of the ionizing background of this magnitude would
violate neither upper limits from H-alpha observations nor the acceptable range
from other measurements.Comment: 30 pages, 9 figures, accepted for Astronomical J. (Oct. 1999
Metal Abundances in the Magellanic Stream
We report on the first metallicity determination for gas in the Magellanic
Stream, using archival HST GHRS data for the background targets Fairall 9, III
Zw 2, and NGC 7469. For Fairall 9, using two subsequent HST revisits and new
Parkes Multibeam Narrowband observations, we have unequivocally detected the
MSI HI component of the Stream (near its head) in SII1250,1253 yielding a
metallicity of [SII/H]=-0.55+/-0.06(r)+/-0.2(s), consistent with either an SMC
or LMC origin and with the earlier upper limit set by Lu et al. (1994). We also
detect the saturated SiII1260 line, but set only a lower limit of
[SiII/H]>-1.5. We present serendipitous detections of the Stream, seen in
MgII2796,2803 absorption with column densities of (0.5-1)x10^13 cm^-2 toward
the Seyfert galaxies III Zw 2 and NGC 7469. These latter sightlines probe gas
near the tip of the Stream (80 deg down-Stream of Fairall 9). For III Zw 2, the
lack of an accurate HI column density and the uncertain MgIII ionization
correction limits the degree to which we can constrain [Mg/H]; a lower limit of
[MgII/HI]>-1.3 was found. For NGC 7469, an accurate HI column density
determination exists, but the extant FOS spectrum limits the quality of the
MgII column density determination, and we conclude that [MgII/HI]>-1.5.
Ionization corrections associated with MgIII and HII suggest that the
corresponding [Mg/H] may range lower by 0.3-1.0 dex. However, an upward
revision of 0.5-1.0 dex would be expected under the assumption that the Stream
exhibits a dust depletion pattern similar to that seen in the Magellanic
Clouds. Remaining uncertainties do not allow us to differentiate between an LMC
versus SMC origin to the Stream gas.Comment: 30 pages, 8 figures, LaTeX (aaspp4), also available at
http://casa.colorado.edu/~bgibson/publications.html, accepted for publication
in The Astronomical Journa
Extremely metal-poor Lyman limit system at z = 2.917 toward the quasar HE 0940-1050
We report on detailed Monte Carlo inversion analysis of the Lyman limit
system observed at z = 2.917 in the VLT/UVES spectrum of the quasar HE
0940-1050. Metal absorption lines of carbon and silicon in three ionization
stages and numerous atomic hydrogen lines have been analyzed simultaneously. It
is found that in order to match the observations, the shape of the ultraviolet
background ionizing spectrum of Haardt & Madau (1996) should be modified: a
spectrum with a higher intensity of the emission feature at 3 Ryd is required.
It is also found that synthetic galactic spectra (or different mixtures of them
with power law spectra) cannot reproduce the observations, indicating that the
stellar contribution to the ionizing background is negligible at z ~= 3. For
the first time a very low carbon abundance of [C/H] = -2.93+/-0.13 and the
abundance ratio [Si/C] = 0.35+/-0.15 are directly measured in the Lyman limit
system with N(H I) = 3.2 10^{17} cm^{-2}. If the absorber at z = 2.917 provides
an example of a pristine gas enriched by the nucleosynthetic products of early
generations of stars, then the measured value of [Si/C] seems to indicate that
the initial mass functions for these stellar populations are constrained to
intermediate masses, M_up <= 25M_solar.Comment: 7 pages, 4 figures, A&A in pres
Does the Milky Way Produce a Nuclear Galactic Wind?
We detect high-velocity absorbing gas using Hubble Space Telescope and Far
Ultraviolet Spectroscopic Explorer medium resolution spectroscopy along two
high-latitude AGN sight lines (Mrk 1383 and PKS 2005-489) above and below the
Galactic Center (GC). These absorptions are most straightforwardly interpreted
as a wind emanating from the GC which does not escape from the Galaxy's
gravitational potential. Spectra of four comparison B stars are used to
identify and remove foreground velocity components from the absorption-line
profiles of O VI, N V, C II, C III, C IV, Si II, Si III, and Si IV. Two
high-velocity (HV) absorption components are detected along each AGN sight
line, three redshifted and one blueshifted. Assuming that the four HV features
trace a large-scale Galactic wind emanating from the GC, the blueshifted
absorber is falling toward the GC at a velocity of 250 +/- 20 km/s, which can
be explained by "Galactic fountain" material that originated in a bound
Galactic wind. The other three absorbers represent outflowing material; the
largest derived outflow velocity is +250 +/- 20 km/s, which is only 45% of the
velocity necessary for the absorber to escape from its current position in the
Galactic gravitational potential. All four HV absorbers are found to reach the
same maximum height above the Galactic plane (|z_max| = 12 +/- 1 kpc), implying
that they were all ejected from the GC with the same initial velocity. The
derived metallicity limits of >10-20% Solar are lower than expected for
material recently ejected from the GC unless these absorbers also contain
significant amounts of hotter gas in unseen ionization stages.Comment: 39 pages, 3 figures, ApJ accepte
Body odor quality predicts behavioral attractiveness in humans
Growing effort is being made to understand how different attractive physical traits co-vary within individuals, partly because this might indicate an underlying index of genetic quality. In humans, attention has focused on potential markers of quality such as facial attractiveness, axillary odor quality, the second-to-fourth digit (2D:4D) ratio and body mass index (BMI). Here we extend this approach to include visually-assessed kinesic cues (nonverbal behavior linked to movement) which are statistically independent of structural physical traits. The utility of such kinesic cues in mate assessment is controversial, particularly during everyday conversational contexts, as they could be unreliable and susceptible to deception. However, we show here that the attractiveness of nonverbal behavior, in 20 male participants, is predicted by perceived quality of their axillary body odor. This finding indicates covariation between two desirable traits in different sensory modalities. Depending on two different rating contexts (either a simple attractiveness rating or a rating for long-term partners by 10 female raters not using hormonal contraception), we also found significant relationships between perceived attractiveness of nonverbal behavior and BMI, and between axillary odor ratings and 2D:4D ratio. Axillary odor pleasantness was the single attribute that consistently predicted attractiveness of nonverbal behavior. Our results demonstrate that nonverbal kinesic cues could reliably reveal mate quality, at least in males, and could corroborate and contribute to mate assessment based on other physical traits
Systematic identification of signaling pathways with potential to confer anticancer drug resistance
Cancer cells can activate diverse signaling pathways to evade the cytotoxic action of drugs. We created and screened a library of barcoded pathway-activating mutant complementary DNAs to identify those that enhanced the survival of cancer cells in the presence of 13 clinically relevant, targeted therapies. We found that activation of the RAS-MAPK (mitogen-activated protein kinase), Notch1, PI3K (phosphoinositide 3-kinase)–mTOR (mechanistic target of rapamycin), and ER (estrogen receptor) signaling pathways often conferred resistance to this selection of drugs. Activation of the Notch1 pathway promoted acquired resistance to tamoxifen (an ER-targeted therapy) in serially passaged breast cancer xenografts in mice, and treating mice with a γ-secretase inhibitor to inhibit Notch signaling restored tamoxifen sensitivity. Markers of Notch1 activity in tumor tissue correlated with resistance to tamoxifen in breast cancer patients. Similarly, activation of Notch1 signaling promoted acquired resistance to MAPK inhibitors in BRAF[superscript V600E] melanoma cells in culture, and the abundance of Notch1 pathway markers was increased in tumors from a subset of melanoma patients. Thus, Notch1 signaling may be a therapeutic target in some drug-resistant breast cancers and melanomas. Additionally, multiple resistance pathways were activated in melanoma cell lines with intrinsic resistance to MAPK inhibitors, and simultaneous inhibition of these pathways synergistically induced drug sensitivity. These data illustrate the potential for systematic identification of the signaling pathways controlling drug resistance that could inform clinical strategies and drug development for multiple types of cancer. This approach may also be used to advance clinical options in other disease contexts.National Institutes of Health (U.S.) (Grant CA103866)National Institutes of Health (U.S.) (Grant AI07389
Cosmic Origins Spectrograph and FUSE Observations of T ~ 10^5 K Gas In A Nearby Galaxy Filament
We present a detection of a broad Ly-alpha absorber (BLA) with a matching O
VI line in the nearby universe. The BLA is detected at z = 0.01028 in the high
S/N spectrum of Mrk 290 obtained using the Cosmic Origins Spectrograph. The
Ly-alpha absorption has two components, with b(HI) = 55 +/- 1 km/s and b(HI) =
33 +/- 1 km/s, separated in velocity by v ~ 115 km/s. The O VI, detected by
FUSE at z = 0.01027, has a b(OVI) = 29 +/- 3 km/s and is kinematically well
aligned with the broader HI component. The different line widths of the BLA and
OVI suggest a temperature of T = 1.4 x 10^5 K in the absorber. The observed
line strength ratios and line widths favor an ionization scenario in which both
ion-electron collisions and UV photons contribute to the ionization in the gas.
Such a model requires a low-metallicity of -1.7 dex, ionization parameter of
log U ~ -1.4, a large total hydrogen column density of N(H) ~ 4 x 10^19 cm^-2,
and a path length of 400 kpc. The line of sight to Mrk 290 intercepts at the
redshift of the absorber, a megaparsec scale filamentary structure extending
over 20 deg in the sky, with several luminous galaxies distributed within 1.5
Mpc projected distance from the absorber. The collisionally ionized gas in this
absorber is likely tracing a shock-heated gaseous structure, consistent with a
few different scenarios for the origin, including an over-dense region of the
WHIM in the galaxy filament or highly ionized gas in the extended halo of one
of the galaxies in the filament. In general, BLAs with metals provide an
efficient means to study T ~ 10^5 - 10^6 K gas in galaxy halos and in the
intergalactic medium. A substantial fraction of the baryons "missing" from the
present universe is predicted to be in such environments in the form of highly
ionized plasma.Comment: Astrophysical Journal Accepte
An Introduction to Gas Accretion onto Galaxies
Evidence for gas accretion onto galaxies can be found throughout the
universe. In this chapter, I summarize the direct and indirect signatures of
this process and discuss the primary sources. The evidence for gas accretion
includes the star formation rates and metallicities of galaxies, the evolution
of the cold gas content of the universe with time, numerous indirect indicators
for individual galaxies, and a few direct detections of inflow. The primary
sources of gas accretion are the intergalactic medium, satellite gas and
feedback material. There is support for each of these sources from observations
and simulations, but the methods with which the fuel ultimately settles in to
form stars remain murky.Comment: 14 pages, 5 figures, Invited review to appear in Gas Accretion onto
Galaxies, Astrophysics and Space Science Library, eds. A. J. Fox & R. Dav\'e,
to be published by Springe
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