335 research outputs found
Globular Clusters: DNA of Early-Type galaxies?
This paper explores if the mean properties of Early-Type Galaxies (ETG) can
be reconstructed from "genetic" information stored in their GCs (i.e., in their
chemical abundances, spatial distributions and ages). This approach implies
that the formation of each globular occurs in very massive stellar
environments, as suggested by some models that aim at explaining the presence
of multi-populations in these systems. The assumption that the relative number
of globular clusters to diffuse stellar mass depends exponentially on chemical
abundance, [Z/H], and the presence of two dominant GC sub-populations blue and
red, allows the mapping of low metallicity halos and of higher metallicity (and
more heterogeneous) bulges. In particular, the masses of the low-metallicity
halos seem to scale up with dark matter mass through a constant. We also find a
dependence of the globular cluster formation efficiency with the mean projected
stellar mass density of the galaxies within their effective radii. The analysis
is based on a selected sub-sample of galaxies observed within the ACS Virgo
Cluster Survey of the {\it Hubble Space Telescope}. These systems were grouped,
according to their absolute magnitudes, in order to define composite fiducial
galaxies and look for a quantitative connection with their (also composite)
globular clusters systems. The results strengthen the idea that globular
clusters are good quantitative tracers of both baryonic and dark matter in
ETGs.Comment: 20 pages, 28 figures and 5 table
Steady-state magneto-optical trap of fermionic strontium on a narrow-line transition
A steady-state magneto-optical trap (MOT) of fermionic strontium atoms
operating on the 7.5 kHz-wide transition
is demonstrated. This MOT features atoms, a loading rate of
atoms/s, and an average temperature of 12 K. These
parameters make it well suited to serve as a source of atoms for
continuous-wave superradiant lasers operating on strontium's mHz-wide clock
transition. Such lasers have only been demonstrated using pulsed Sr sources,
limiting their range of applications. Our MOT makes an important step toward
continuous operation of these devices, paving the way for continuous-wave
active optical clocks.Comment: 11 pages, 7 figure
Continuous Bose-Einstein condensation
Bose-Einstein condensates (BECs) are macroscopic coherent matter waves that
have revolutionized quantum science and atomic physics. They are essential to
quantum simulation and sensing, for example underlying atom interferometers in
space and ambitious tests of Einstein's equivalence principle. The key to
dramatically increasing the bandwidth and precision of such matter-wave sensors
lies in sustaining a coherent matter wave indefinitely. Here we demonstrate
continuous Bose-Einstein condensation by creating a continuous-wave (CW)
condensate of strontium atoms that lasts indefinitely. The coherent matter wave
is sustained by amplification through Bose-stimulated gain of atoms from a
thermal bath. By steadily replenishing this bath while achieving 1000x higher
phase-space densities than previous works, we maintain the conditions for
condensation. This advance overcomes a fundamental limitation of all atomic
quantum gas experiments to date: the need to execute several cooling stages
time-sequentially. Continuous matter-wave amplification will make possible CW
atom lasers, atomic counterparts of CW optical lasers that have become
ubiquitous in technology and society. The coherence of such atom lasers will no
longer be fundamentally limited by the atom number in a BEC and can ultimately
reach the standard quantum limit. Our development provides a new, hitherto
missing piece of atom optics, enabling the construction of continuous coherent
matter-wave devices. From infrasound gravitational wave detectors to optical
clocks, the dramatic improvement in coherence, bandwidth and precision now
within reach will be decisive in the creation of a new class of quantum
sensors.Comment: 17 pages, 10 figure
Culturable aerobic and facultative bacteria from the gut of the polyphagic dung beetle Thorectes lusitanicus Jeckel
Unlike other dung beetles, the Iberian geotrupid Thorectes lusitanicus exhibits polyphagous behavior; for example, it is able to eat acorns, fungi, fruits, and carrion in addition to the dung of different mammals. This adaptation to digest a wider diet has physiological and developmental advantages and requires key changes in the composition and diversity of the beetle's gut microbiota. In this study, we isolated aerobic, facultative anaerobic, and aerotolerant microbiota amenable to grow in culture from the gut contents of T. lusitanicus and resolved isolate identity to the species level by sequencing 16S rRNA gene fragments. Using BLAST similarity searches and maximum likelihood phylogenetic analyses, we were able to reveal that the analyzed fraction (culturable, aerobic, facultative anaerobic, and aerotolerant) of beetle gut microbiota is dominated by the phyla Proteobacteria, Firmicutes and Actinobacteria. Among Proteobacteria, members of the order Enterobacteriales (Gammaproteobacteria) were the most abundant. The main functions associated with the bacteria found in the gut of T. lusitanicus would likely include nitrogen fixation, denitrification, detoxification, and diverse defensive roles against pathogens.This study was supported by the project 065/2002 of the Ministry of Environment, and the projects “Thorbellota” (CGL2008/03878/BOS) and “NiTerDist” (CGL2011-515 25544) of the Secretaría de Estado de Investigación, Desarrollo e Innovación
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