274 research outputs found
The SAMI Galaxy Survey: Revising the Fraction of Slow Rotators in IFS Galaxy Surveys
The fraction of galaxies supported by internal rotation compared to galaxies
stabilized by internal pressure provides a strong constraint on galaxy
formation models. In integral field spectroscopy surveys, this fraction is
biased because survey instruments typically only trace the inner parts of the
most massive galaxies. We present aperture corrections for the two most widely
used stellar kinematic quantities and . Our
demonstration involves integral field data from the SAMI Galaxy Survey and the
ATLAS Survey. We find a tight relation for both and
when measured in different apertures that can be used as a linear
transformation as a function of radius, i.e., a first-order aperture
correction. We find that and radial growth curves are
well approximated by second order polynomials. By only fitting the inner
profile (0.5), we successfully recover the profile out to one
if a constraint between the linear and quadratic parameter in the
fit is applied. However, the aperture corrections for and
derived by extrapolating the profiles perform as well as applying
a first-order correction. With our aperture-corrected
measurements, we find that the fraction of slow rotating galaxies increases
with stellar mass. For galaxies with 11, the fraction
of slow rotators is percent, but is underestimated if galaxies
without coverage beyond one are not included in the sample
( percent). With measurements out to the largest aperture radius
the slow rotator fraction is similar as compared to using aperture corrected
values ( percent). Thus, aperture effects can significantly bias
stellar kinematic IFS studies, but this bias can now be removed with the method
outlined here.Comment: Accepted for Publication in the Monthly Notices of the Royal
Astronomical Society. 16 pages and 11 figures. The key figures of the paper
are: 1, 4, 9, and 1
The SAMI Galaxy Survey: Shocks and Outflows in a normal star-forming galaxy
We demonstrate the feasibility and potential of using large integral field
spectroscopic surveys to investigate the prevalence of galactic-scale outflows
in the local Universe. Using integral field data from SAMI and the Wide Field
Spectrograph, we study the nature of an isolated disk galaxy, SDSS
J090005.05+000446.7 (z = 0.05386). In the integral field datasets, the galaxy
presents skewed line profiles changing with position in the galaxy. The skewed
line profiles are caused by different kinematic components overlapping in the
line-of-sight direction. We perform spectral decomposition to separate the line
profiles in each spatial pixel as combinations of (1) a narrow kinematic
component consistent with HII regions, (2) a broad kinematic component
consistent with shock excitation, and (3) an intermediate component consistent
with shock excitation and photoionisation mixing. The three kinematic
components have distinctly different velocity fields, velocity dispersions,
line ratios, and electron densities. We model the line ratios, velocity
dispersions, and electron densities with our MAPPINGS IV shock and
photoionisation models, and we reach remarkable agreement between the data and
the models. The models demonstrate that the different emission line properties
are caused by major galactic outflows that introduce shock excitation in
addition to photoionisation by star-forming activities. Interstellar shocks
embedded in the outflows shock-excite and compress the gas, causing the
elevated line ratios, velocity dispersions, and electron densities observed in
the broad kinematic component. We argue from energy considerations that, with
the lack of a powerful active galactic nucleus, the outflows are likely to be
driven by starburst activities. Our results set a benchmark of the type of
analysis that can be achieved by the SAMI Galaxy Survey on large numbers of
galaxies.Comment: 17 pages, 15 figures. Accepted to MNRAS. References update
The SAMI Galaxy Survey: Global stellar populations on the size-mass plane
We present an analysis of the global stellar populations of galaxies in the
SAMI Galaxy Survey. Our sample consists of 1319 galaxies spanning four orders
of magnitude in stellar mass and includes all morphologies and environments. We
derive luminosity-weighted, single stellar population equivalent stellar ages,
metallicities and alpha enhancements from spectra integrated within one
effective radius apertures. Variations in galaxy size explain the majority of
the scatter in the age--mass and metallicity--mass relations. Stellar
populations vary systematically in the plane of galaxy size and stellar mass,
such that galaxies with high stellar surface mass density are older, more
metal-rich and alpha-enhanced than less dense galaxies. Galaxies with high
surface mass densities have a very narrow range of metallicities, however, at
fixed mass, the spread in metallicity increases substantially with increasing
galaxy size (decreasing density). We identify residual correlations with
morphology and environment. At fixed mass and size, galaxies with late-type
morphologies, small bulges and low Sersic n are younger than early-type, high
n, high bulge-to-total galaxies. Age and metallicity both show small residual
correlations with environment; at fixed mass and size, galaxies in denser
environments or more massive halos are older and somewhat more metal rich than
those in less dense environments. We connect these trends to evolutionary
tracks within the size--mass plane.Comment: 25 pages, 18 figures, MNRAS in press Corrected typo in author lis
Sleep-Disordered Breathing and Mortality: A Prospective Cohort Study
In a cohort of 6,441 volunteers followed over an average of 8.2 years, Naresh Punjabi and colleagues find sleep-disordered breathing to be independently associated with mortality and identify predictive characteristics
The SAMI Galaxy Survey: a new method to estimate molecular gas surface densities from star formation rates
Stars form in cold molecular clouds. However, molecular gas is difficult to observe because the most abundant molecule (H_2) lacks a permanent dipole moment. Rotational transitions of CO are often used as a tracer of H_2, but CO is much less abundant and the conversion from CO intensity to H2 mass is often highly uncertain. Here we present a new method for estimating the column density of cold molecular gas (Σ_(gas)) using optical spectroscopy. We utilize the spatially resolved Hα maps of flux and velocity dispersion from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey. We derive maps of Σ_(gas) by inverting the multi-freefall star formation relation, which connects the star formation rate surface density (Σ_(SFR)) with Σ_(gas) and the turbulent Mach number (M). Based on the measured range of Σ_(SFR) = 0.005-1.5M⊙ yr^(−1) kpc^(−2) and M=18–130, we predict Σ_(gas) = 7–200 M⊙ pc^(−2)
in the star-forming regions of our sample of 260 SAMI galaxies. These values are close to previously measured Σ_(gas) obtained directly with unresolved CO observations of similar galaxies at low redshift. We classify each galaxy in our sample as ‘star-forming’ (219) or ‘composite/AGN/shock’ (41), and find that in ‘composite/AGN/shock’ galaxies the average Σ_(SFR),
M and Σ_(gas) are enhanced by factors of 2.0, 1.6 and 1.3, respectively, compared to star-forming galaxies. We compare our predictions of Σ_(gas) with those obtained by inverting the Kennicutt–Schmidt relation and find that our new method is a factor of 2 more accurate in predicting Σ_(gas), with an average deviation of 32 per cent from the actual Σ_(gas)
Metabolic imaging across scales reveals distinct prostate cancer phenotypes
Hyperpolarised magnetic resonance imaging (HP-13C-MRI) has shown promise as a clinical tool for detecting and characterising prostate cancer. Here we use a range of spatially resolved histological techniques to identify the biological mechanisms underpinning differential [1-13C]lactate labelling between benign and malignant prostate, as well as in tumours containing cribriform and non-cribriform Gleason pattern 4 disease. Here we show that elevated hyperpolarised [1-13C]lactate signal in prostate cancer compared to the benign prostate is primarily driven by increased tumour epithelial cell density and vascularity, rather than differences in epithelial lactate concentration between tumour and normal. We also demonstrate that some tumours of the cribriform subtype may lack [1-13C]lactate labelling, which is explained by lower epithelial lactate dehydrogenase expression, higher mitochondrial pyruvate carrier density, and increased lipid abundance compared to lactate-rich non-cribriform lesions. These findings highlight the potential of combining spatial metabolic imaging tools across scales to identify clinically significant metabolic phenotypes in prostate cancer
First Dinosaur Tracks from the Arabian Peninsula
Background: The evolutionary history of Mesozoic terrestrial vertebrates from the Arabian Peninsula is virtually unknown. Despite vast exposures of rocky outcrops, only a handful of fossils have yet been described from the region. Here we report a multi-taxon dinosaur track assemblage near Madar village, 47 km north of Sana’a, Republic of Yemen. This represents the first dinosaur tracksite from the Arabian Peninsula, and the only multi-taxon dinosaur ichnosite in the Middle East. Methodology/Findings: Measurements were taken directly from trackway impressions, following standard ichnological conventions. The presence of bipedal trackmakers is evidenced by a long series of pes imprints preserving smoothly rounded posterior margins, no evidence of a hallux, bluntly rounded digit tips and digital divarication angles characteristic of ornithopod dinosaurs. Nearby, eleven parallel quadrupedal trackways document a sauropod herd that included large and small individuals traveling together. Based on the morphology of manus impressions along with a narrow-gauged stance, the quadrupedal trackways were made by non-titanosauriform neosauropods. Additional isolated tracks and trackways of sauropod and ornithopod dinosaurs are preserved nearby. Conclusions/Significance: Taken together, these discoveries present the most evocative window to date into the evolutionary history of dinosaurs of the Arabian Peninsula. Given the limited Mesozoic terrestrial record from the region, this discovery is of both temporal and geographic significance, and massive exposures of similarly-aged outcrops nearby offe
The ocean sampling day consortium
Ocean Sampling Day was initiated by the EU-funded Micro B3 (Marine Microbial Biodiversity, Bioinformatics, Biotechnology) project to obtain a snapshot of the marine microbial biodiversity and function of the world’s oceans. It is a simultaneous global mega-sequencing campaign aiming to generate the largest standardized microbial data set in a single day. This will be achievable only through the coordinated efforts of an Ocean Sampling Day Consortium, supportive partnerships and networks between sites. This commentary outlines the establishment, function and aims of the Consortium and describes our vision for a sustainable study of marine microbial communities and their embedded functional traits
The SAMI Galaxy Survey: : extraplanar gas, galactic winds, and their association with star formation history
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ©: 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society, the version of record is available on line at doi: 10.1093/mnras/stw017We investigate a sample of 40 local, main-sequence, edge-on disc galaxies using integral field spectroscopy with the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey to understand the link between properties of the extraplanar gas and their host galaxies. The kinematics properties of the extraplanar gas, including velocity asymmetries and increased dispersion, are used to differentiate galaxies hosting large-scale galactic winds from those dominated by the extended diffuse ionized gas. We find rather that a spectrum of diffuse gas-dominated to wind dominated galaxies exist. The wind-dominated galaxies span a wide range of star formation rates () across the whole stellar mass range of the sample (). The wind galaxies also span a wide range in SFR surface densities () that is much lower than the canonical threshold of . The wind galaxies on average have higher SFR surface densities and higher values than those without strong wind signatures. The enhanced indicates that bursts of star formation in the recent past are necessary for driving large-scale galactic winds. We demonstrate with Sloan Digital Sky Survey data that galaxies with high SFR surface density have experienced bursts of star formation in the recent past. Our results imply that the galactic winds revealed in our study are indeed driven by bursts of star formation, and thus probing star formation in the time domain is crucial for finding and understanding galactic winds.Peer reviewe
The SAMI Galaxy Survey: Gravitational Potential and Surface Density Drive Stellar Populations. I. Early-type Galaxies
The well-established correlations between the mass of a galaxy and the properties of its stars are considered to be evidence for mass driving the evolution of the stellar population (SP). However, for early-type galaxies (ETGs), we find that g - i color and stellar metallicity [Z/H] correlate more strongly with gravitational potential Φ than with mass M, whereas SP age correlates best with surface density Σ. Specifically, for our sample of 625 ETGs with integral-field spectroscopy from the Sydney-AAO Multi-object Integral-field Galaxy Survey, compared to correlations with mass, the color-Φ, [Z/H]-Φ, and age-Σ relations show both a smaller scatter and a lower residual trend with galaxy size. For the star formation duration proxy [α/Fe], we find comparable results for trends with Φ and Σ, with both being significantly stronger than the [α/Fe]-M relation. In determining the strength of a trend, we analyze both the overall scatter, and the observational uncertainty on the parameters, in order to compare the intrinsic scatter in each correlation. These results lead us to the following inferences and interpretations: (1) the color-Φ diagram is a more precise tool for determining the developmental stage of the SP than the conventional color-mass diagram; and (2) gravitational potential is the primary regulator of global stellar metallicity, via its relation to the gas escape velocity. Furthermore, we propose the following two mechanisms for the age and [α/Fe] relations with Σ: (a) the age-Σ and [α/Fe]-Σ correlations arise as results of compactness-driven quenching mechanisms; and/or (b) as fossil records of the relation in their disk-dominated progenitors.The SAMI Galaxy Survey is based on observations made at
the Anglo-Australian Telescope. The SAMI spectrograph was
developed jointly by the University of Sydney and the
Australian Astronomical Observatory. The SAMI input catalog
is based on data from the Sloan Digital Sky Survey, the GAMA
Survey and the VST ATLAS Survey. The SAMI Galaxy
Survey is funded by the Australian Research Council Centre of
Excellence for All-sky Astrophysics (CAASTRO; grant
CE110001020), and other participating institutions.
Parts of this research was conducted by the Australian
Research Council Centre of Excellence for All Sky Astrophysics
in 3 Dimensions (ASTRO 3D), through project number
CE170100013.
T.M.B. is supported by an Australian Government Research
Training Program Scholarship. N.S. acknowledges a University
of Sydney Postdoctoral Research Fellowship. J.v.d.S. is funded
under J.B.-H.’s ARC Laureate Fellowship (FL140100278). S.B.
and M.S.O. acknowledge Australian Research Council Future
Fellowships (FT140101166 and FT140100255). A.M.M. acknowledges
NASA Hubble Fellowship (HST-HF2-51377) from
the Space Telescope Science Institute, operated by Association
of Universities for Research in Astronomy, Inc., for NASA
(NAS5-26555
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