An Infrared Coronagraphic Survey for Substellar Companions

We have used the F160W filter (1.4-1.8 um) and the coronagraph on the Near-InfraRed Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope (HST) to survey 45 single stars with a median age of 0.15 Gyr, an average distance of 30 pc, and an average H-magnitude of 7 mag. For the median age we were capable of detecting a 30 M_Jup companion at separations between 15 and 200 AU. A 5 M_Jup object could have been detected at 30 AU around 36% of our primaries. For several of our targets that were less than 30 Myr old, the lower mass limit was as low as a Jupiter mass, well into the high mass planet region. Results of the entire survey include the proper motion verification of five low-mass stellar companions, two brown dwarfs (HR7329B and TWA5B) and one possible brown dwarf binary (Gl 577B/C).Comment: 11 figures, accepted by A

Externally Occulted Terrestrial Planet Finder Coronagraph: Simulations and Sensitivities

A multitude of coronagraphic techniques for the space-based direct detection and characterization of exo-solar terrestrial planets are actively being pursued by the astronomical community. Typical coronagraphs have internal shaped focal plane and/or pupil plane occulting masks which block and/or diffract starlight thereby increasing the planet's contrast with respect to its parent star. Past studies have shown that any internal technique is limited by the ability to sense and control amplitude, phase (wavefront) and polarization to exquisite levels - necessitating stressing optical requirements. An alternative and promising technique is to place a starshade, i.e. external occulter, at some distance in front of the telescope. This starshade suppresses most of the starlight before entering the telescope - relaxing optical requirements to that of a more conventional telescope. While an old technique it has been recently been advanced by the recognition that circularly symmetric graded apodizers can be well approximated by shaped binary occulting masks. Indeed optimal shapes have been designed that can achieve smaller inner working angles than conventional coronagraphs and yet have high effective throughput allowing smaller aperture telescopes to achieve the same coronagraphic resolution and similar sensitivity as larger ones. Herein we report on our ongoing modeling, simulation and optimization of external occulters and show sensitivity results with respect to number and shape errors of petals, spectral passband, accuracy of Fresnel propagation, and show results for both filled and segmented aperture telescopes and discuss acquisition and sensing of the occulter's location relative to the telescope

Genetic architecture of human plasma lipidome and its link to cardiovascular disease

AbstractUnderstanding genetic architecture of plasma lipidome could provide better insights into lipid metabolism and its link to cardiovascular diseases (CVDs). Here, we perform genome-wide association analyses of 141 lipid species (n = 2,181 individuals), followed by phenome-wide scans with 25 CVD related phenotypes (n = 511,700 individuals). We identify 35 lipid-species-associated loci (P −8), 10 of which associate with CVD risk including five new loci-COL5A1, GLTPD2, SPTLC3, MBOAT7 and GALNT16 (false discovery rateAbstract Understanding genetic architecture of plasma lipidome could provide better insights into lipid metabolism and its link to cardiovascular diseases (CVDs). Here, we perform genome-wide association analyses of 141 lipid species (n = 2,181 individuals), followed by phenome-wide scans with 25 CVD related phenotypes (n = 511,700 individuals). We identify 35 lipid-species-associated loci (P <5 ×10−8), 10 of which associate with CVD risk including five new loci-COL5A1, GLTPD2, SPTLC3, MBOAT7 and GALNT16 (false discovery rate<0.05). We identify loci for lipid species that are shown to predict CVD e.g., SPTLC3 for CER(d18:1/24:1). We show that lipoprotein lipase (LPL) may more efficiently hydrolyze medium length triacylglycerides (TAGs) than others. Polyunsaturated lipids have highest heritability and genetic correlations, suggesting considerable genetic regulation at fatty acids levels. We find low genetic correlations between traditional lipids and lipid species. Our results show that lipidomic profiles capture information beyond traditional lipids and identify genetic variants modifying lipid levels and risk of CVD

Chromosome Xq23 is associated with lower atherogenic lipid concentrations and favorable cardiometabolic indices

AbstractAutosomal genetic analyses of blood lipids have yielded key insights for coronary heart disease (CHD). However, X chromosome genetic variation is understudied for blood lipids in large sample sizes. We now analyze genetic and blood lipid data in a high-coverage whole X chromosome sequencing study of 65,322 multi-ancestry participants and perform replication among 456,893 European participants. Common alleles on chromosome Xq23 are strongly associated with reduced total cholesterol, LDL cholesterol, and triglycerides (min P = 8.5 × 10−72), with similar effects for males and females. Chromosome Xq23 lipid-lowering alleles are associated with reduced odds for CHD among 42,545 cases and 591,247 controls (P = 1.7 × 10−4), and reduced odds for diabetes mellitus type 2 among 54,095 cases and 573,885 controls (P = 1.4 × 10−5). Although we observe an association with increased BMI, waist-to-hip ratio adjusted for BMI is reduced, bioimpedance analyses indicate increased gluteofemoral fat, and abdominal MRI analyses indicate reduced visceral adiposity. Co-localization analyses strongly correlate increased CHRDL1 gene expression, particularly in adipose tissue, with reduced concentrations of blood lipids.Abstract Autosomal genetic analyses of blood lipids have yielded key insights for coronary heart disease (CHD). However, X chromosome genetic variation is understudied for blood lipids in large sample sizes. We now analyze genetic and blood lipid data in a high-coverage whole X chromosome sequencing study of 65,322 multi-ancestry participants and perform replication among 456,893 European participants. Common alleles on chromosome Xq23 are strongly associated with reduced total cholesterol, LDL cholesterol, and triglycerides (min P = 8.5 × 10−72), with similar effects for males and females. Chromosome Xq23 lipid-lowering alleles are associated with reduced odds for CHD among 42,545 cases and 591,247 controls (P = 1.7 × 10−4), and reduced odds for diabetes mellitus type 2 among 54,095 cases and 573,885 controls (P = 1.4 × 10−5). Although we observe an association with increased BMI, waist-to-hip ratio adjusted for BMI is reduced, bioimpedance analyses indicate increased gluteofemoral fat, and abdominal MRI analyses indicate reduced visceral adiposity. Co-localization analyses strongly correlate increased CHRDL1 gene expression, particularly in adipose tissue, with reduced concentrations of blood lipids

Constraining Galaxy Evolution Using Observed UV-Optical Spectra

Our understanding of galaxy evolution depends on model spectra of stellar populations, and the models are only as good as the observed spectra and stellar parameters that go into them. We are therefore evaluating modem UV-optical model spectra using Hubble's Next Generation Spectral Library (NGSL) as the reference standard. The NGSL comprises intermediate-resolution (R is approximately 1000) STIS spectra of 378 stars having a wide range in metallicity and age. Unique features of the NGSL include its broad wavelength coverage (1,800-10,100 A) and high-S/N, absolute spectrophotometry. We will report on a systematic comparison of model and observed UV-blue spectra, describe where on the HR diagram significant differences occur, and comment on current approaches to correct the models for these differences

Observing the First Stars in Luminous, Red Galaxies

Modern cosmological simulations predict that the first stars are to be found today in luminous, red galaxies. Although observing such stars individually against a background of younger, metal-rich stars is impossible, the first stars should make their presence known by their strong, line-free ultraviolet flux. We have found evidence for a UV-bright stellar population in Sloan spectra of LRG's at z=0.4-0.5. We present arguments for interpreting this UV-bright stellar population as the oldest stars, rather than other types of stellar populations (e.g. young stars or blue straggler stars in the dominant, metal-rich stellar populatio

Ultraviolet Spectral Diagnostics

At redshifts, z>l, the rest-frame mid-UV is brought into view of large, ground-based telescopes. Here, we report on a study of the potential of the rest-frame UV spectrum for deriving the age since the last major episode of star formation in a galaxy. We base this investigation on wide-band (0.2-1.0 microns), low-resolution (R-1000) spectra of single stars in Hubble's Next Generation Spectral Library (NGSL). We find that a combination of mid-UV spectral indices and colors can indeed yield the age of a stellar population, but only if light from the stellar population is unreddened

Luminous Red Galaxies at Z=0.4-0.5

We report on a study of approx.20,000 luminous red galaxies (LRG's) at z=0.4-0.5 observed by the Sloan Digital Sky Survey. In order to differentiate among them, we measured restframe magnitudes, u (3000-3500 A), b (4200-4800 A), and y (5700-6300 A) from the spectra themselves. The galaxies show a significant range in restframe colors and absolute magnitudes. We binned the spectra according to the restframe u-b color and y-band absolute magnitude in order to increase the S/N. We used 3 approaches to estimate the ages and metal content of these binned spectra: via their spectral energy distributions, from spectral-line indices, and by full spectral fitting. The three methods usually produce discordant result