3,255 research outputs found
Triaxial orbit-based modelling of the Milky Way Nuclear Star Cluster
We construct triaxial dynamical models for the Milky Way nuclear star cluster
using Schwarzschild's orbit superposition technique. We fit the stellar
kinematic maps presented in Feldmeier et al. (2014). The models are used to
constrain the supermassive black hole mass M_BH, dynamical mass-to-light ratio
M/L, and the intrinsic shape of the cluster. Our best-fitting model has M_BH =
(3.0 +1.1 -1.3)x10^6 M_sun, M/L = (0.90 +0.76 -0.08) M_sun/L_{sun,4.5micron},
and a compression of the cluster along the line-of-sight. Our results are in
agreement with the direct measurement of the supermassive black hole mass using
the motion of stars on Keplerian orbits. The mass-to-light ratio is consistent
with stellar population studies of other galaxies in the mid-infrared. It is
possible that we underestimate M_BH and overestimate the cluster's triaxiality
due to observational effects. The spatially semi-resolved kinematic data and
extinction within the nuclear star cluster bias the observations to the near
side of the cluster, and may appear as a compression of the nuclear star
cluster along the line-of-sight. We derive a total dynamical mass for the Milky
Way nuclear star cluster of M_MWNSC = (2.1 +-0.7)x10^7 M_sun within a sphere
with radius r = 2 x r_eff = 8.4 pc. The best-fitting model is tangentially
anisotropic in the central r = 0.5-2 pc of the nuclear star cluster, but close
to isotropic at larger radii. Our triaxial models are able to recover complex
kinematic substructures in the velocity map.Comment: 14 pages, 10 figures. Accepted for publication in MNRA
The role of severity and intentionality in the intensity of Schadenfreude attribution:A developmental study of Danish children
Asymptotically free scalar curvature-ghost coupling in Quantum Einstein Gravity
We consider the asymptotic-safety scenario for quantum gravity which
constructs a non-perturbatively renormalisable quantum gravity theory with the
help of the functional renormalisation group. We verify the existence of a
non-Gaussian fixed point and include a running curvature-ghost coupling as a
first step towards the flow of the ghost sector of the theory. We find that the
scalar curvature-ghost coupling is asymptotically free and RG relevant in the
ultraviolet. Most importantly, the property of asymptotic safety discovered so
far within the Einstein-Hilbert truncation and beyond remains stable under the
inclusion of the ghost flow.Comment: 8 pages, 3 figures, RevTe
The unique contribution of vocabulary in the reading development of English as a foreign language
Molecular gas at supernova local environments unveiled by EDGE
CO observations allow estimations of the gas content of molecular clouds,
which trace the reservoir of cold gas fuelling star formation, as well as to
determine extinction via H column density, N(H). Here, we studied
millimetric and optical properties at 26 supernovae (SNe) locations of
different types in a sample of 23 nearby galaxies by combining molecular
CO (J = 1 0) resolved maps from the EDGE survey and
optical Integral Field Spectroscopy from the CALIFA survey. We found an even
clearer separation between type II and type Ibc SNe in terms of molecular gas
than what we found in the optical using H emission as a proxy for
current SF rate, which reinforces the fact that SNe Ibc are more associated
with SF-environments. While A at SN locations is similar for SNe II and SNe
Ibc, and higher compared to SNe Ia, N(H) is significantly higher for SNe
Ibc than for SNe II and SNe Ia. When compared to alternative extinction
estimations directly from SN photometry and spectroscopy, we find that our SNe
Ibc have also redder color excess but showed standard Na I D absorption
pseudo-equivalent widths (1 \AA). In some cases we find no extinction
when estimated from the environment, but high amounts of extinction when
measured from SN observations, which suggests that circumstellar material or
dust sublimation may be playing a role. This work serves as a benchmark for
future studies combining last generation millimeter and optical IFS instruments
to reveal the local environmental properties of extragalactic SNe.Comment: MNRAS accepted, 17 pages, 8 Figures, 4 Table
Resolving the age bimodality of galaxy stellar populations on kpc scales
Galaxies in the local Universe are known to follow bimodal distributions in
the global stellar populations properties. We analyze the distribution of the
local average stellar-population ages of 654,053 sub-galactic regions resolved
on ~1-kpc scales in a volume-corrected sample of 394 galaxies, drawn from the
CALIFA-DR3 integral-field-spectroscopy survey and complemented by SDSS imaging.
We find a bimodal local-age distribution, with an old and a young peak
primarily due to regions in early-type galaxies and star-forming regions of
spirals, respectively. Within spiral galaxies, the older ages of bulges and
inter-arm regions relative to spiral arms support an internal age bimodality.
Although regions of higher stellar-mass surface-density, mu*, are typically
older, mu* alone does not determine the stellar population age and a bimodal
distribution is found at any fixed mu*. We identify an "old ridge" of regions
of age ~9 Gyr, independent of mu*, and a "young sequence" of regions with age
increasing with mu* from 1-1.5 Gyr to 4-5 Gyr. We interpret the former as
regions containing only old stars, and the latter as regions where the relative
contamination of old stellar populations by young stars decreases as mu*
increases. The reason why this bimodal age distribution is not inconsistent
with the unimodal shape of the cosmic-averaged star-formation history is that
i) the dominating contribution by young stars biases the age low with respect
to the average epoch of star formation, and ii) the use of a single average age
per region is unable to represent the full time-extent of the star-formation
history of "young-sequence" regions.Comment: 17 pages, 11 figures, MNRAS accepte
Discovery of a Quadruple Lens in CANDELS with a Record Lens Redshift z=1.53
Using spectroscopy from the Large Binocular Telescope and imaging from the
Hubble Space Telescope we discovered the first strong galaxy lens at z(lens)>1.
The lens has a secure photometric redshift of z=1.53+/-0.09 and the source is
spectroscopically confirmed at z=3.417. The Einstein radius (0.35"; 3.0 kpc)
encloses 7.6 x 10^10 Msol, with an upper limit on the dark matter fraction of
60%. The highly magnified (40x) source galaxy has a very small stellar mass
(~10^8 Msol) and shows an extremely strong [OIII]_5007A emission line (EW_0 ~
1000A) bolstering the evidence that intense starbursts among very low-mass
galaxies are common at high redshift.Comment: accepted for publication in ApJ Letter
Balmer-dominated shocks in Tycho's SNR: omnipresence of CRs
We present wide-field, spatially and highly resolved spectroscopic
observations of Balmer filaments in the northeastern rim of Tycho's supernova
remnant in order to investigate the signal of cosmic-ray (CR) acceleration. The
spectra of Balmer-dominated shocks (BDSs) have characteristic narrow (FWHM
10 kms) and broad (FWHM 1000 kms) H
components. CRs affect the H-line parameters: heating the cold neutrals
in the interstellar medium results in broadening of the narrow H-line
width beyond 20 kms, but also in reduction of the broad H-line
width due to energy being removed from the protons in the post-shock region.
For the first time we show that the width of the narrow H line, much
larger than 20 kms, is not a resolution or geometric effect nor a
spurious result of a neglected intermediate (FWHM 100 kms)
component resulting from hydrogen atoms undergoing charge exchange with warm
protons in the broad-neutral precursor. Moreover, we show that a narrow line
width 20 kms extends across the entire NE rim, implying CR
acceleration is ubiquitous, and making it possible to relate its strength to
locally varying shock conditions. Finally, we find several locations along the
rim, where spectra are significantly better explained (based on Bayesian
evidence) by inclusion of the intermediate component, with a width of 180
kms on average.Comment: Proceeding for contributed talk at the IAU Symposium No. 331: "SN
1987A, 30 years later - Cosmic Rays and Nuclei from Supernovae and their
Aftermaths", 2017, La Reunion Island; References correcte
Balmer filaments in Tycho's supernova remnant: an interplay between cosmic-ray and broad-neutral precursors
We present H spectroscopic observations and detailed modelling of the
Balmer filaments in the supernova remnant Tycho. We used Galaxy H
Fabry-P\'erot Spectrometer on the William Herschel Telescope with a
3.4'3.4' field-of-view, 0.2" pixel scale and \sigma_\rm{instr}=8.1
km/s resolution at 1" seeing for hours, resulting in 82
spatial-spectral bins that resolve the narrow H line in the entire
Tycho's northeastern rim. For the first time, we can mitigate artificial line
broadening from unresolved differential motion, and probe H emission
parameters in varying shock and ambient medium conditions. Broad H line
remains unresolved within spectral coverage of 392 km/s. We employed Bayesian
inference to obtain reliable parameter confidence intervals, and quantify the
evidence for models with multiple line components. The median H
narrow-line full-width at half-maximum of all bins and models is
W_\rm{NL}=(54.8\pm1.8) km/s at the confidence level, varying within
[35, 72] km/s between bins and clearly broadened compared to the intrinsic
(thermal) km/s. Possible line splits are accounted for, significant
in of the filament, and presumably due to remaining projection
effects. We also find wide-spread evidence for intermediate-line emission of a
broad-neutral precursor, with median W_\rm{IL}=(180\pm14) km/s (
confidence). Finally, we present a measurement of the remnant's systemic
velocity, V_\rm{LSR}=-34 km/s, and map differential line-of-sight motions.
Our results confirm the existence and interplay of shock precursors in Tycho's
remnant. In particular, we show that suprathermal narrow-line emission is
near-universal in Tycho and that, in absence of an alternative explanation,
collisionless supernova remnant shocks constitute a viable acceleration source
for Galactic TeV Cosmic-Ray protons.Comment: 36 pages, 17 figures, 5 tables, Paper accepted for publication in the
Astrophysical Journal; References correcte
The effect of unresolved binaries on globular cluster proper-motion dispersion profiles
High-precision kinematic studies of globular clusters require an accurate knowledge of all possible sources of contamination. Amongst other sources, binary stars can introduce systematic biases in the kinematics. Using a set of Monte Carlo cluster simulations with different concentrations and binary fractions, we investigate the effect of unresolved binaries on proper-motion dispersion profiles, treating the simulations like HST propermotion samples. Since globular clusters evolve towards a state of partial energy equipartition, more massive stars lose energy and decrease their velocity dispersion. As a consequence, on average, binaries have a lower velocity dispersion, since they are more massive kinematic tracers. We show that, in the case of clusters with high binary fraction (initial binary fraction of 50%) and high concentration (i.e., closer to energy equipartition), unresolved binaries introduce a color-dependent bias in the velocity dispersion of main-sequence stars of the order of 0.1-0.3 km s^-1 (corresponding to 1 − 6% of the velocity dispersion), with the reddest stars having a lower velocity dispersion, due to the higher fraction of contaminating binaries. This bias depends on the ability to distinguish binaries from single stars, on the details of the color-magnitude diagram and the photometric errors. We apply our analysis to the HSTPROMO data set of NGC 7078 (M15) and show that no effect ascribable to binaries is observed, consistent with the low binary fraction of the cluster. Our work indicates that binaries do not significantly bias proper-motion velocity-dispersion profiles, but should be taken into account in the error budget of kinematic analyses
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