41 research outputs found
Metallicity Distribution Functions, Radial Velocities, and Alpha Element Abundances in Three Off-Axis Bulge Fields
We present radial velocities and chemical abundance ratios of [Fe/H], [O/Fe],
[Si/Fe], and [Ca/Fe] for 264 red giant branch (RGB) stars in three Galactic
bulge off-axis fields located near (l,b)=(-5.5,-7), (-4,-9), and (+8.5,+9). The
results are based on equivalent width and spectrum synthesis analyses of
moderate resolution (R~18,000), high signal-to-noise ratio (S/N~75-300) spectra
obtained with the Hydra spectrographs on the Blanco 4m and WIYN 3.5m
telescopes. The targets were selected from the blue side of the giant branch to
avoid cool stars that would be strongly affected by CN and TiO; however, a
comparison of the color-metallicity distribution in literature samples suggests
our selection of bluer targets should not present a significant bias against
metal-rich stars. We find a full range in metallicity that spans
[Fe/H]\approx-1.5 to +0.5, and that, in accordance with the previously observed
minor-axis vertical metallicity gradient, the median [Fe/H] also declines with
increasing Galactic latitude in off-axis fields. The off-axis vertical [Fe/H]
gradient in the southern bulge is estimated to be ~0.4 dex/kpc. The (+8.5,+9)
field exhibits a higher than expected metallicity, with a median [Fe/H]=-0.23,
that might be related to a stronger presence of the X--shaped bulge structure
along that line-of-sight. All fields exhibit an identical, strong decrease in
velocity dispersion with increasing metallicity that is consistent with
observations in similar minor-axis outer bulge fields. Additionally, the
[O/Fe], [Si/Fe], and [Ca/Fe] versus [Fe/H] trends are identical among our three
fields, and are in good agreement with past bulge studies. [abridged]Comment: Accepted for Publication in the Astrophysical Journal; 120 pages
(main text ends on page 24); 22 figures (figures end on page 46); 6 tables;
electronic versions of the tables can be made available upon request to
author C. Johnso
The Blanco DECam Bulge Survey (BDBS) VIII: Chemo-kinematics in the southern Galactic bulge from 2.3 million red clump stars with Gaia DR3 proper motions
The Blanco DECam Bulge Survey (BDBS) provides near-ultraviolet to
near-infrared photometry for ~250 million unique stars. By combining BDBS
photometry with the latest Gaia astrometry, we characterize the chemo-dynamics
of red clump stars across the BDBS footprint, using an unprecedented sample
size and sky coverage. We construct a sample of ~2.3 million red clump giants
in the bulge with photometric metallicities, BDBS photometric distances, and
proper motions. We study the kinematics of the red clump stars as a function of
sky position and metallicity, by investigating proper motion rotation curves,
velocity dispersions, and proper motion correlations across the southern
Galactic bulge. We find that metal-poor red clump stars exhibit lower rotation
amplitudes, at ~29 km s kpc^{-1}. The peak of the angular velocity is
~39 km s^{-1} kpc^{-1} for [Fe/H] ~ -0.2 dex, exhibiting declining rotation at
higher [Fe/H]. The velocity dispersion is higher for metal-poor stars, while
metal-rich stars show a steeper gradient with Galactic latitude, with a maximum
dispersion at low latitudes along the bulge minor axis. Only metal-rich stars
([Fe/H] >~ -0.5 dex) show clear signatures of the bar in their kinematics,
while the metal-poor population exhibits isotropic motions with an axisymmetric
pattern around Galactic longitude l = 0. This work reports the largest sample
of bulge stars with distance, metallicity, and astrometry and shows clear
kinematic differences with metallicity. The global kinematics over the bulge
agrees with earlier studies. However, we see striking changes with increasing
metallicity and for the first time, see kinematic differences for stars with
[Fe/H]>-0.5, suggesting that the bar itself may have kinematics that depends on
metallicity.Comment: 12 pages, Accepted for publication in A&
Mast Cell–Derived Particles Deliver Peripheral Signals to Remote Lymph Nodes
During infection, signals from the periphery are known to reach draining lymph nodes (DLNs), but how these molecules, such as inflammatory cytokines, traverse the significant distances involved without dilution or degradation remains unclear. We show that peripheral mast cells, upon activation, release stable submicrometer heparin-based particles containing tumor necrosis factor and other proteins. These complexes enter lymphatic vessels and rapidly traffic to the DLNs. This physiological drug delivery system facilitates communication between peripheral sites of inflammation and remote secondary lymphoid tissues
Before the bar:kinematic detection of a spheroidal metal-poor bulge component
We present 947 radial velocities of RR Lyrae variable stars in four fields located toward the Galactic bulge, observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay (BRAVA-RR). We show that these RR Lyrae stars (RRLs) exhibit hot kinematics and null or negligible rotation and are therefore members of a separate population from the bar/pseudobulge that currently dominates the mass and luminosity of the inner Galaxy. Our RRLs predate these structures and have metallicities, kinematics, and spatial distribution that are consistent with a "classical" bulge, although we cannot yet completely rule out the possibility that they are the metal-poor tail of a more metal-rich ( dex) halo–bulge population. The complete catalog of radial velocities for the BRAVA-RR stars is also published electronically
Diagnosis of prostate cancer by desorption electrospray ionization mass spectrometric imaging of small metabolites and lipids
Accurate identification of prostate cancer in frozen sections at the time of surgery can be challenging, limiting the surgeon's ability to best determine resection margins during prostatectomy. We performed desorption electrospray ionization mass spectrometry imaging (DESI-MSI) on 54 banked human cancerous and normal prostate tissue specimens to investigate the spatial distribution of a wide variety of small metabolites, carbohydrates, and lipids. In contrast to several previous studies, our method included Krebs cycle intermediates (m/z <200), which we found to be highly informative in distinguishing cancer from benign tissue. Malignant prostate cells showed marked metabolic derangements compared with their benign counterparts. Using the "Least absolute shrinkage and selection operator" (Lasso), we analyzed all metabolites from the DESI-MS data and identified parsimonious sets of metabolic profiles for distinguishing between cancer and normal tissue. In an independent set of samples, we could use these models to classify prostate cancer from benign specimens with nearly 90% accuracy per patient. Based on previous work in prostate cancer showing that glucose levels are high while citrate is low, we found that measurement of the glucose/citrate ion signal ratio accurately predicted cancer when this ratio exceeds 1.0 and normal prostate when the ratio is less than 0.5. After brief tissue preparation, the glucose/citrate ratio can be recorded on a tissue sample in 1 min or less, which is in sharp contrast to the 20 min or more required by histopathological examination of frozen tissue specimens. prostate cancer | Krebs cycle | metabolism | desorption electrospray ionization | mass spectrometry P rostate cancer (PCa) is the most commonly diagnosed solidorgan cancer and the second leading cause of cancer death in men in the United States (1). Because of prostate-specific antigen (PSA) screening in the United States, most PCas are discovered when they are confined to the prostate (2). Many of these localized PCas are treated by surgical removal of the entire prostate (radical prostatectomy). The presence of cancer cells at the edge of the surgical resection, or positive surgical margins, is associated with higher rates of recurrence and death from PCa (3, 4). Therefore, an important clinical challenge in PCa management is to devise a rapid and highly accurate method to detect cancerous cells in real time to allow resection of additional periprostatic tissues and reduce cancer recurrence after surgery. Over the last decade, several innovative analytical techniques (5-12) have been developed to distinguish cancer from benign tissue in various organs. However, none has achieved wide clinical adoption for various reasons including inconvenience, narrow information content, unavailability, poor sensitivity, slowness of adoption, and operating room workflow incompatibility. In PCa, intraoperative frozen sections have been used to attempt to identify PCa at the margin based on analysis of histology. However, frozen sections have been shown to have poor sensitivity and specificity for the detection of PCa and currently are not recommended Recently, a label-free molecular imaging method called desorption electrospray ionization mass spectrometric imaging (DESI-MSI) has been developed (15-17). DESI-MSI can rapidly evaluate the tissue metabolome in situ by simultaneously characterizing hundreds of lipids and metabolites. In the last 5 y, reports from our group Given the known alterations in metabolic pathways in PCa, we tested whether DESI-MSI of metabolites and lipids could have utility in discriminating cancer from normal tissue obtained from radical prostatectomy. Using tandem and high-resolution mass spectrometry we have characterized the distinct metabolite and lipid profiles of normal and malignant prostate. Although many earlier DESI-MSI studies considered only lipid profiles in identification of cancer, here we report imaging small metabolite Significance Desorption electrospray ionization mass spectrometry imaging (DESI-MSI) is a label-free molecular imaging technique that provides a window into the biochemical processes present in benign and malignant prostate tissue. This is important both in improving the understanding of tissue biology and in achieving rapid cancer diagnosis. We applied DESI-MSI to record lipid, carbohydrate, and most importantly, small metabolite images from 54 normal and malignant prostate tissue specimens. Several Krebs cycle intermediates were present at different concentrations in prostate cancer compared with normal tissue. Statistical calculations identified panels of metabolites that could readily distinguish prostate cancer from normal tissue with nearly 90% accuracy in a validation set. The results also indicated that the ratio of glucose to citrate ion signals could be used to accurately identify prostate cancer
Blanco DECam Bulge Survey (BDBS) IV: Metallicity Distributions and Bulge Structure from 2.6 Million Red Clump Stars
We present photometric metallicity measurements for a sample of 2.6 million
bulge red clump stars extracted from the Blanco DECam Bulge Survey (BDBS).
Similar to previous studies, we find that the bulge exhibits a strong vertical
metallicity gradient, and that at least two peaks in the metallicity
distribution functions appear at b < -5. We can discern a metal-poor ([Fe/H] ~
-0.3) and metal-rich ([Fe/H] ~ +0.2) abundance distribution that each show
clear systematic trends with latitude, and may be best understood by changes in
the bulge's star formation/enrichment processes. Both groups exhibit asymmetric
tails, and as a result we argue that the proximity of a star to either peak in
[Fe/H] space is not necessarily an affirmation of group membership. The
metal-poor peak shifts to lower [Fe/H] values at larger distances from the
plane while the metal-rich tail truncates. Close to the plane, the metal-rich
tail appears broader along the minor axis than in off-axis fields. We also
posit that the bulge has two metal-poor populations -- one that belongs to the
metal-poor tail of the low latitude and predominantly metal-rich group, and
another belonging to the metal-poor group that dominates in the outer bulge. We
detect the X-shape structure in fields with |Z| > 0.7 kpc and for stars with
[Fe/H] > -0.5. Stars with [Fe/H] < -0.5 may form a spheroidal or "thick bar"
distribution while those with [Fe/H] > -0.1 are strongly concentrated near the
plane.Comment: 26 pages, 22 figures, accepted for publication in MNRAS; the full
data table is very long so only a stub table has been provided here; the full
electronic table will be provided through MNRAS upon publication, but early
access to the full table will be granted upon request to the author