985 research outputs found
High resolution kinematics of galactic globular clusters. II. On the significance of velocity dispersion measurements
Small number statistics may heavily affect the structure of the broadening
function in integrated spectra of galactic globular cluster centers. As a
consequence, it is a priori unknown how closely line broadening measure- ments
gauge the intrinsic velocity dispersions at the cores of these stel- lar
systems. We have tackled this general problem by means of Monte Carlo
simulations. An examination of the mode and the frequency distribution of the
measured values of the simulations indicates that the low value measured for
the velocity dispersion of M30 (Zaggia etal 1992) is likely a reliable estimate
of the velocity dispersion at the center of this cluster. The same methodology
applied to the case of M15 suggests that the steep inward rise of the velocity
dispersion found by Peterson, Seitzer and Cudworth (1989) is real, although
less pronounced. Large-aperture observa- tions are less sensitive to
statistical fluctuations, but are unable to detect strong variations in the
dispersion wich occur within the aperture itself.Comment: 6 pages, 8 figures upon request, Latex A&A style version 3.0,
DAPD-20
Assessing the risks to tesla´s market value: towards the share price
The report evaluates the risks associated with owning Tesla’s stock to provide the investors with an informed investment recommendation. Firstly, Tesla may suffer from the competition undercutting its prices by marketing cheaper models. Secondly, the supply of essential battery components puts the penetration of electric vehicles in Europe and America under considerable pressure. Thirdly, the escalating inflation is scaring investors more than how it is impacting Tesla’s financials. Finally, before drawing a comparison between the long-term RONIC and the cost of capital, the report provides evidence on how Tesla can navigate the supply chain disruption better than its legacy competition
«Isoletta sacra al commercio ed all’arti». Andrea Memmo, Melchiorre Cesarotti e il Prato della Valle come esperimento di riforma del paesaggio urbano
Il contributo esamina, con l’ausilio degli scritti di Melchiorre Cesarotti, genesi e finalità dell’intervento urbano sul Prato della Valle ideato dal Provveditore straordinario di Padova Andrea Memmo. La questione della fiera nel Prato della Valle fu assunta da Memmo come nodo centrale per avviare un più vasto programma di rinnovo urbano che in prospettiva intendeva giungere ad una sistemazione generale della città . La forza riformatrice dell’idea posta a confronto con la realtà urbana e sociale, riuscì solo in parte ad attingere l’esito auspicato: la grande piazza attuale non è che il frammento di un disegno urbano ben più vasto, l’aspirazione di Memmo condivisa anche da Cesarotti
Pre-MS depletion, accretion and primordial 7Li
We reconsider the role of pre-main sequence (pre-MS) Li depletion on the
basis of new observational and theoretical evidence: i) new observations of
Halpha emissions in young clusters show that mass accretion could be continuing
till the first stages of the MS, ii) theoretical implications from
helioseismology suggest large overshooting values below the bottom of the
convective envelopes. We argue here that a significant pre-MS 7Li destruction,
caused by efficient overshoot mixing, could be followed by a matter accretion
after 7Li depletion has ceased on MS thus restoring Li almost to the pristine
value. As a test case we show that a halo dwarf of 0.85 Msun with an extended
overshooting envelope starting with an initial abundance of A(Li) = 2.74 would
burn Li completely, but an accretion rate of the type 1e-8xe^{-t/3e6} Msun
yr would restore Li to end with an A(Li) = 2.31. A self-regulating
process is required to produce similar final values in a range of different
stellar masses to explain the PopII Spite plateau. However, this framework
could explain why open cluster stars have lower Li abundances than the
pre-solar nebula, the absence of Li in the most metal poor dwarfs and a number
of other features which lack of a satisfactory explanation.Comment: To be published in Memorie della Societ\`a Astronomica Italiana
Supplementi Vol. 22, Proceedings of Lithium in the cosmos, Iocco F.,
Bonifacio P., Vangioni E., ed
The Luminosity and Mass Function of the Globular Cluster NGC1261
I-band CCD images of two large regions of the Galactic globular cluster NGC
1261 have been used to construct stellar luminosity functions (LF) for 14000
stars in three annuli from 1.4' from the cluster center to the tidal radius.
The LFs extend to M_I~8 and tend to steepen from the inner to the outer
annulus, in agreement with the predictions of the multimass King-Michie model
that we have calculated for this cluster. The LFs have been transformed into
mass functions. Once corrected for mass segregation the global mass function of
NGC 1261 has a slope x_0=0.8+/-0.5Comment: 9 pages, A&A macros, accepted for publication in A&
Structure and kinematics of the peculiar galaxy NGC 128
This is a multiband photometric and spectroscopic study of the peculiar S0
galaxy NGC128. We present results from broad (B and R) and narrow band optical
CCD photometry, near (NIR) and far (FIR) infrared observations, long slit
spectroscopy, and Fabry-Perot interferometry (CIGALE). The peculiar peanut
shape morphology of the galaxy is observed both at optical and near-infrared
wavelengths. The stellar disk is thick and distorted (arc-bended), with a color
asymmetry along the major axis due to the presence of a large amount of dust,
estimated through NIR and FIR data of ~6x10^6 M_sun, in the region of
interaction with the companion galaxy NGC127. The color maps are nearly uniform
over the whole galaxy, but for the major axis asymmetry, and a small gradient
toward the center indicating the presence of a redder disk-like component. The
H_alpha image indeed reveals the existence of a tilted gaseous ``disk'' around
the center, oriented with the major axis toward the companion galaxy NGC127.
Long slit and CIGALE data confirm the presence of gas in a disk-like component
counter-rotating and inclined approximately of 50 deg. to the line of sight.
The mass of the gas disk in the inner region is ~2.7x10^4 M_sun. The stellar
velocity field is cylindrical up to the last measured points of the derived
rotation curves, while the velocity dispersion profiles are typical for an S0
galaxy, but for an extended constant behaviour along the minor axis.Comment: accepted for pubblication in A&A Supp
Extended stellar kinematics of elliptical galaxies in the Fornax cluster
We present extended stellar kinematics for a sample of 13 elliptical galaxies
in the Fornax cluster. Major-axis velocity dispersion profiles (VDPs) and
rotation curves (RCs) are given for 12 of the galaxies. A major feature of this
data is the spatial extension: for 8 galaxies the data extends beyond 1 R_e,
and for 5 it extends beyond 2 R_e. Compared to the previously available data,
this corresponds to an increase in spatial coverage by a factor from 1 to 5.
Five of the ellipticals in the sample turn out to be rotationally-supported
systems, having positive rotation parameter log (V/sigma)*. One of these five,
and another 3 galaxies from the remaining sample, display evidence for bar-like
kinematics. The data indicate that the true number of `dynamically hot' stellar
systems, is much lower than previously thought: of the Es in the present sample
only 1/4 are confirmed as `pressure-supported' systems. The data reveal a host
of individual peculiarities, like: wiggles, strong gradients, and asymmetries
in the rotation curve and/or in the velocity dispersion profile, thus showing
that the presence of kinematically distinct components and/or triaxiality is a
common characteristic of this class of object.Comment: 27 pages, includes 15 eps figures. Accepted for publication in A&A
Sup
The Earth transiting the Sun as seen from Jupiter's moons: detection of an inverse Rossiter-McLaughlin effect produced by the Opposition Surge of the icy Europa
We report on a multi-wavelength observational campaign which followed the
Earth's transit on the Sun as seen from Jupiter on 5 Jan the 2014. Simultaneous
observations of Jupiter's moons Europa and Ganymede obtained with HARPS from La
Silla, Chile, and HARPS-N from La Palma, Canary Islands, were performed to
measure the Rossiter-McLaughlin effect due to the Earth's passage using the
same technique successfully adopted for the 2012 Venus Transit (Molaro et al
2013). The expected modulation in radial velocities was of about 20 cm/s but an
anomalous drift as large as 38 m/s, i.e. more than two orders of magnitude
higher and opposite in sign, was detected instead. The consistent behaviour of
the two spectrographs rules out instrumental origin of the radial velocity
drift and BiSON observations rule out the possible dependence on the Sun's
magnetic activity. We suggest that this anomaly is produced by the Opposition
Surge on Europa's icy surface, which amplifies the intensity of the solar
radiation from a portion of the solar surface centered around the crossing
Earth which can then be observed as a a sort of inverse Rossiter-McLaughling
effect. in fact, a simplified model of this effect can explain in detail most
features of the observed radial velocity anomalies, namely the extensions
before and after the transit, the small differences between the two
observatories and the presence of a secondary peak closer to Earth passage.
This phenomenon, observed here for the first time, should be observed every
time similar Earth alignments occur with rocky bodies without atmospheres. We
predict it should be observed again during the next conjunction of Earth and
Jupiter in 2026.Comment: 9 pages, 7 figure
- …