We have investigated the abundance of calcium in early-type galaxies by measuring the strength of the Ca I l4227 absorption line in their integrated spectra. The database used is the large sample of ...early-type galaxy integrated spectra in Caldwell and coworkers. We have measured Ca abundances from the Ca I l4227 feature both by using the Lick Ca4227 index and by defining a new index, Ca4227r, that avoids the CN4216 molecular band in the continuum on the blueward side of the line. With the new index definition we measure Ca abundances that are systematically ~0.3 dex higher than with the Lick Ca4227 index. The result is that with the new index definition we obtain higher Ca/Fe abundances in early-type galaxies, which are more consistent with their well-known Mg/Fe overabundances. Hence, we suggest that Ca might be slightly enhanced, relative to Fe, in early-type galaxies.
As part of this paper we present radial velocities and rotational velocities of over 200 M dwarfs, with a v sin i precision of ~2 km s super(-1) and a measurement floor at v sin i = 4 km s super(-1). ...This survey significantly increases the number of M dwarfs studied for rotational velocities and radial velocity variability (at ~100-200 m s super(-1)), and will inform and advance the target selection for planned radial velocity and photometric searches for low-mass exoplanets around M dwarfs, such as the Habitable Zone Planet Finder, CARMENES, and TESS. Multiple epochs of radial velocity observations enable us to identify short period binaries, and adaptive optics imaging of a subset of stars enables the detection of possible stellar companions at larger separations. The high-resolution APOGEE spectra, covering the entire H band, provide the opportunity to measure physical stellar parameters such as effective temperatures and metallicities for many of these stars.
We map the trends of elemental abundance ratios across the Galactic disk, spanning R = 3 - 15 kpc and midplane distance Z = 0 - 2 kpc , for 15 elements in a sample of 20,485 stars measured by the ...SDSS/APOGEE survey (O, Na, Mg, Al, Si, P, S, K, Ca, V, Cr, Mn, Fe, Co, Ni). Adopting Mg rather than Fe as our reference element, and separating stars into two populations based on Fe/Mg, we find that the median trends of X/Mg versus Mg/H in each population are nearly independent of location in the Galaxy. The full multi-element cartography can be summarized by combining these nearly universal median sequences with our measured metallicity distribution functions and the relative proportions of the low-Fe/Mg (high- ) and high-Fe/Mg (low- ) populations, which depend strongly on R and Z . We interpret the median sequences with a semi-empirical "two-process" model that describes both the ratio of core collapse and Type Ia supernova (SN Ia) contributions to each element and the metallicity dependence of the supernova yields. These observationally inferred trends can provide strong tests of supernova nucleosynthesis calculations. Our results lead to a relatively simple picture of abundance ratio variations in the Milky Way, in which the trends at any location can be described as the sum of two components with relative contributions that change systematically and smoothly across the Galaxy. Deviations from this picture and future extensions to other elements can provide further insights into the physics of stellar nucleosynthesis and unusual events in the Galaxy's history.
Crotamine is a peptide toxin from the venom of the rattlesnake
Crotalus durissus terrificus that induces a typical hind-limb paralysis of unknown nature. Hind limbs have a predominance of ...fast-twitching muscles that bear a higher density of sodium channels believed until now to be the primary target of crotamine. Hypothetically, this makes these muscles more sensitive to crotamine and would explain such hind-limb paralysis. To challenge this hypothesis, we performed concentration vs. response curves on fast (extensor digitorum longus (EDL)) and slow (soleus) muscles of adult male rats. Crotamine was tested on various human Na
+ channel isoforms (Na
v1.1–Na
v1.6
α-subunits) expressed in HEK293 cells in patch-clamp experiments, as well as in acutely dissociated dorsal root ganglion (DRG) neurons. Also, the behavioral effects of crotamine intoxication were compared with those of a muscle-selective sodium channel antagonist
μ-CgTx-GIIIA, and other sodium-acting toxins such as tetrodotoxin
α- and
β-pompilidotoxins, sea anemone toxin BcIII, spider toxin Tx2-6. Results pointed out that EDL was more susceptible to crotamine than soleus under direct electrical stimulation. Surprisingly, electrophysiological experiments in human Na
v1.1 to Na
v1.6 Na
+ channels failed to show any significant change in channel characteristics, in a clear contrast with former studies. DRG neurons did not respond to crotamine. The behavioral effects of the toxins were described in detail and showed remarkable differences. We conclude that, although differences in the physiology of fast and slow muscles may cause the typical crotamine syndrome, sodium channels are not the primary target of crotamine and therefore, the real mechanism of action of this toxin is still unknown.
ABSTRACT
Studies of the kinematics and chemical compositions of Galactic globular clusters (GCs) enable the reconstruction of the history of star formation, chemical evolution, and mass assembly of ...the Galaxy. Using the latest data release (DR16) of the SDSS/APOGEE survey, we identify 3090 stars associated with 46 GCs. Using a previously defined kinematic association, we break the sample down into eight separate groups and examine how the kinematics-based classification maps into chemical composition space, considering only α (mostly Si and Mg) elements and Fe. Our results show that (i) the loci of both in situ and accreted subgroups in chemical space match those of their field counterparts; (ii) GCs from different individual accreted subgroups occupy the same locus in chemical space. This could either mean that they share a similar origin or that they are associated with distinct satellites which underwent similar chemical enrichment histories; (iii) the chemical compositions of the GCs associated with the low orbital energy subgroup defined by Massari and collaborators is broadly consistent with an in situ origin. However, at the low-metallicity end, the distinction between accreted and in situ populations is blurred; (iv) regarding the status of GCs whose origin is ambiguous, we conclude the following: the position in Si–Fe plane suggests an in situ origin for Liller 1 and a likely accreted origin for NGC 5904 and NGC 6388. The case of NGC 288 is unclear, as its orbital properties suggest an accretion origin, its chemical composition suggests it may have formed in situ.
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) provides spectroscopic information of regions of the inner Milky Way, which are inaccessible to optical surveys. We present the ...first large study of the metallicity distribution of the innermost Galactic regions based on high-quality measurements for 7545 red giant stars within 4.5 kpc of the Galactic center, with the goal to shed light on the structure and origin of the Galactic bulge. Stellar metallicities are found, through multiple Gaussian decompositions, to be distributed in several components, which is indicative of the presence of various stellar populations such as the bar or the thin and the thick disks. Super-solar (Fe/H = +0.32) and solar (Fe/H = +0.00) metallicity components, tentatively associated with the thin disk and the Galactic bar, respectively, seem to be major contributors near the midplane. A solar-metallicity component extends outwards in the midplane but is not observed in the innermost regions. The central regions (within 3 kpc of the Galactic center) reveal, on the other hand, the presence of a significant metal-poor population (Fe/H = −0.46), tentatively associated with the thick disk, which becomes the dominant component far from the midplane ( kpc). Varying contributions from these different components produce a transition region at +0.5 kpc , characterized by a significant vertical metallicity gradient.
We derive age constraints for 1639 red giants in the APOKASC sample for which seismic parameters from Kepler, as well as effective temperatures, metallicities and α/Fe values from APOGEE DR12 (Apache ...Point Observatory Galactic Evolution Experiment Data Release 12) are available. We investigate the relation between age and chemical abundances for these stars, using a simple and robust approach to obtain ages. We first derive stellar masses using standard seismic scaling relations, then determine the maximum possible age for each star as function of its mass and metallicity, independently of its evolutionary stage. While the overall trend between maximum age and chemical abundances is a declining fraction of young stars with increasing α/Fe, at least 14 out of 241 stars with α/Fe >0.13 are younger than 6 Gyr. Five stars with α/Fe ≥0.2 have ages below 4 Gyr. We examine the effect of modifications in the standard seismic scaling relations, as well as the effect of very low helium fractions, but these changes are not enough to make these stars as old as usually expected for α-rich stars (i.e. ages greater than 8–9 Gyr). Such unusual α-rich young stars have also been detected by other surveys, but defy simple explanations in a galaxy evolution context.
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