216 research outputs found
A fractional matter sector for general relativity
In this work, we construct a fractional matter sector for general relativity.
In particular, we propose a suitable fractional anisotropy function relating
both the tangential and radial pressure of a spherically symmetric fluid based
on the Gr\"unwald-Letnikov fractional derivative. The system is closed by
implementing the polytropic equation of state for the radial pressure. We solve
the system of integro-differential equations by Euler's method and explore the
behavior of the physical quantities, namely, the normalized density energy, the
normalized mass function, and the compactness
Flat rotation curves and low velocity dispersions in KMOS star-forming galaxies at z ~ 1
The study of the evolution of star-forming galaxies requires the
determination of accurate kinematics and scaling relations out to high
redshift. In this paper we select a sample of 18 galaxies at z~1, observed in
the H-alpha emission-line with KMOS, to derive accurate kinematics using a
novel 3D analysis technique. We use the new code 3D-Barolo, that models the
galaxy emission directly in the 3D observational space, without the need to
extract kinematic maps. This technique's major advantage is that it is not
affected by beam smearing and thus it enables the determination of rotation
velocity and intrinsic velocity dispersion, even at low spatial resolution. We
find that: 1) the rotation curves of these z~1 galaxies rise very steeply
within few kiloparsecs and remain flat out to the outermost radius and 2) the
H-alpha velocity dispersions are low, ranging from 15 to 40 km/s, which leads
to V/sigma = 3-10. These characteristics are similar to those of disc galaxies
in the local Universe. Finally, we also report no significant evolution of the
stellar-mass Tully-Fisher relation. Our results show that disc galaxies are
kinematically mature and rotation-dominated already at z~1.Comment: Accepted for publication in A&A, 11 pages, 6 figures, 1 tabl
The angular momentum of disc galaxies at z=1
We investigate the relation between stellar mass and specific stellar angular
momentum, or `Fall relation', for a sample of 17 isolated, regularly rotating
disc galaxies at z=1. All galaxies have a) rotation curves determined from
Halpha emission-line data; b) HST imaging in optical and infrared filters; c)
robust determinations of their stellar masses. We use HST images in f814w and
f160w filters, roughly corresponding to rest-frames B and I bands, to extract
surface brightness profiles for our systems. We robustly bracket the specific
angular momentum by assuming that rotation curves beyond the outermost Halpha
rotation point stay either flat or follow a Keplerian fall-off. By comparing
our measurements with those determined for disc galaxies in the local Universe,
we find no evolution in the Fall relation in the redshift range 0<z<1,
regardless of the band used and despite the uncertainties in the stellar
rotation curves at large radii. This result holds unless stellar masses at z=1
are systematically underestimated by more than 50%. Our findings are compatible
with expectations based on a LCDM cosmological framework and support a scenario
where both the stellar Tully-Fisher and mass-size relations for spirals do not
evolve significantly in this redshift range.Comment: 11 pages, 4 figures, 1 table. Accepted by A&
A highly-ionized region surrounding SN Refsdal revealed by MUSE
Supernova (SN) Refsdal is the first multiply-imaged, highly-magnified, and
spatially-resolved SN ever observed. The SN exploded in a highly-magnified
spiral galaxy at z=1.49 behind the Frontier Fields Cluster MACS1149, and
provides a unique opportunity to study the environment of SNe at high z. We
exploit the time delay between multiple images to determine the properties of
the SN and its environment, before, during, and after the SN exploded. We use
the integral-field spectrograph MUSE on the VLT to simultaneously target all
observed and model-predicted positions of SN Refsdal. We find MgII emission at
all positions of SN Refsdal, accompanied by weak FeII* emission at two
positions. The measured ratios of [OII] to MgII emission of 10-20 indicate a
high degree of ionization with low metallicity. Because the same high degree of
ionization is found in all images, and our spatial resolution is too coarse to
resolve the region of influence of SN Refsdal, we conclude that this high
degree of ionization has been produced by previous SNe or a young and hot
stellar population. We find no variability of the [OII] line over a period of
57 days. This suggests that there is no variation in the [OII] luminosity of
the SN over this period, or that the SN has a small contribution to the
integrated [OII] emission over the scale resolved by our observations.Comment: 5 pages, 4 figures, accepted for publication in A&
The 3D Kinematics of Gas in the Small Magellanic Cloud
We investigate the kinematics of neutral gas in the Small Magellanic Cloud
(SMC) and test the hypothesis that it is rotating in a disk. To trace the 3D
motions of the neutral gas distribution, we identify a sample of young, massive
stars embedded within it. These are stars with radial velocity measurements
from spectroscopic surveys and proper motion measurements from Gaia, whose
radial velocities match with dominant HI components. We compare the observed
radial and tangential velocities of these stars with predictions from the
state-of-the-art rotating disk model based on high-resolution 21 cm
observations of the SMC from the Australian Square Kilometer Array Pathfinder
telescope. We find that the observed kinematics of gas-tracing stars are
inconsistent with disk rotation. We conclude that the kinematics of gas in the
SMC are more complex than can be inferred from the integrated radial velocity
field. As a result of violent tidal interactions with the LMC, non-rotational
motions are prevalent throughout the SMC, and it is likely composed of distinct
sub-structures overlapping along the line of sight.Comment: 9 pages, 5 figures, 1 Appendix; ApJ accepte
The envelope protein of Usutu virus attenuates West Nile virus virulence in immunocompetent mice
West Nile virus (WNV) and Usutu virus (USUV) are the two most widespread mosquito-borne flaviviruses in Europe causing severe neuroinvasive disease in humans. Here, following standardization of the murine model with wild type (wt) viruses, we engineered WNV and USUV genome by reverse genetics. A recombinant virus carrying the 5′ UTR of WNV within the USUV genome backbone (r-USUV5′-UTR WNV) was rescued; when administered to mice this virus did not cause signs or disease as wt USUV suggesting that 5′ UTR of a marked neurotropic parental WNV was not per se a virulence factor. Interestingly, a chimeric virus carrying the envelope (E) protein of USUV in the WNV genome backbone (r-WNVE-USUV) showed an attenuated profile in mice compared to wt WNV but significantly more virulent than wt USUV. Moreover, except when tested against serum samples originating from a live WNV infection, r-WNVE-USUV showed an identical antigenic profile to wt USUV confirming that E is also the major immunodominant protein of USUV
Epidemiology, pathological aspects and genome heterogeneity of feline morbillivirus in Italy
Feline morbillivirus (FeMV) is an emerging morbillivirus first described in cats less than a decade ago. FeMV has been associated with chronic kidney disease of cats characterized by tubulointerstitial nephritis (TIN), although this aspect is still controversial and not demonstrated with certainty. To investigate FeMV prevalence and genomic characteristics, an epidemiological survey was conducted in a total number of 127 household cats originating from two Italian regions, Abruzzi and Emilia-Romagna. A total number of 69 cats originating from three feline colonies were also enrolled for the study. Correlation with TIN was investigated by employing a total number of 35 carcasses. Prevalence of FeMV RNA was higher in urine samples collected from cats of colonies (P = 31.8%, CI 95% 22.1–43.6) compared to household cats (P = 8.66%, CI 95% 4.9–14.9) and in young and middle-aged cats while prevalence of FeMV Abs was higher in old cats. Sequences obtained straight from infected biological samples, either partial or complete, cluster into two clades within FeMV genotype 1, distantly related to FeMV genotype 2. Immunohistochemistry analysis of kidney sections of FeMV RNA positive cats revealed immunoreactivity within epithelial cells of renal tubuli and inflammatory cells. However, statistically significant association between FeMV and renal damages, including TIN, was not demonstrated (p= 0.0695, Fisher exact test). By virus histochemistry performed with FeMV-negative feline tissues and a FeMV isolate, tropism for different cellular types such as inflammatory cells residing in blood vessels of kidney and brain, airway epithelial cells, alveolar macrophages and to a lesser extent, the central nervous system, was demonstrated. Additional studies are warranted in order to establish viral tropism and immune response during the early phases of infection and to disentangle the role of FeMV in co-infection processes
The PUMA project. III. Incidence and properties of ionised gas disks in ULIRGs, associated velocity dispersion and its dependence on starburstiness
A classical scenario suggests that ULIRGs transform colliding spiral galaxies
into a spheroid dominated early-type galaxy. Recent high-resolution simulations
have instead shown that, under some circumstances, rotation disks can be
preserved during the merging process or rapidly regrown after coalescence. Our
goal is to analyze in detail the ionised gas kinematics in a sample of ULIRGs
to infer the incidence of gas rotational dynamics in late-stage interacting
galaxies and merger remnants. We analysed MUSE data of a sample of 20 nearby
(z<0.165) ULIRGs, as part of the "Physics of ULIRGs with MUSE and ALMA" (PUMA)
project. We found that 27% individual nuclei are associated with kpc-scale
disk-like gas motions. The rest of the sample displays a plethora of gas
kinematics, dominated by winds and merger-induced flows, which make the
detection of rotation signatures difficult. On the other hand, the incidence of
stellar disk-like motions is ~2 times larger than gaseous disks, as the former
are probably less affected by winds and streams. The eight galaxies with a
gaseous disk present relatively high intrinsic gas velocity dispersion (sigma =
30-85 km/s), rotationally-supported motions (with gas rotation velocity over
velocity dispersion vrot/sigma > 1-8), and dynamical masses in the range
(2-7)x1e10 Msun. By combining our results with those of local and high-z disk
galaxies from the literature, we found a significant correlation between sigma
and the offset from the main sequence (MS), after correcting for their
evolutionary trends. Our results confirm the presence of kpc-scale rotating
disks in interacting galaxies and merger remnants, with an incidence going from
27% (gas) to ~50% (stars). The ULIRGs gas velocity dispersion is up to a factor
of ~4 higher than in local normal MS galaxies, similar to high-z starbursts as
presented in the literature
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