6,933 research outputs found
The Black Hole in the Compact, High-dispersion Galaxy NGC 1271
Located in the Perseus cluster, NGC 1271 is an early-type galaxy with a small
effective radius of 2.2 kpc and a large stellar velocity dispersion of 276 km/s
for its K-band luminosity of 8.9x10^{10} L_sun. We present a mass measurement
for the black hole in this compact, high-dispersion galaxy using observations
from the integral field spectrograph NIFS on the Gemini North telescope
assisted by laser guide star adaptive optics, large-scale integral field unit
observations with PPAK at the Calar Alto Observatory, and Hubble Space
Telescope WFC3 imaging observations. We are able to map out the stellar
kinematics on small spatial scales, within the black hole sphere of influence,
and on large scales that extend out to four times the galaxy's effective
radius. We find that the galaxy is rapidly rotating and exhibits a sharp rise
in the velocity dispersion. Through the use of orbit-based stellar dynamical
models, we determine that the black hole has a mass of (3.0^{+1.0}_{-1.1}) x
10^9 M_sun and the H-band stellar mass-to-light ratio is 1.40^{+0.13}_{-0.11}
M_sun/L_sun (1-sigma uncertainties). NGC 1271 occupies the sparsely-populated
upper end of the black hole mass distribution, but is very different from the
Brightest Cluster Galaxies (BCGs) and giant elliptical galaxies that are
expected to host the most massive black holes. Interestingly, the black hole
mass is an order of magnitude larger than expectations based on the galaxy's
bulge luminosity, but is consistent with the mass predicted using the galaxy's
bulge stellar velocity dispersion. More compact, high-dispersion galaxies need
to be studied using high spatial resolution observations to securely determine
black hole masses, as there could be systematic differences in the black hole
scaling relations between these types of galaxies and the BCGs/giant
ellipticals, thereby implying different pathways for black hole and galaxy
growth.Comment: accepted for publication in Ap
The structural and dynamical properties of compact elliptical galaxies
Dedicated photometric and spectroscopic surveys have provided unambiguous
evidence for a strong stellar mass-size evolution of galaxies within the last
10 Gyr. The likely progenitors of today's most massive galaxies are remarkably
small, disky, passive and have already assembled much of their stellar mass at
redshift z=2. An in-depth analysis of these objects, however, is currently not
feasible due to the lack of high-quality, spatially-resolved photometric and
spectroscopic data. In this paper, we present a sample of nearby compact
elliptical galaxies (CEGs), which bear resemblance to the massive and quiescent
galaxy population at earlier times. Hubble Space Telescope (HST) and wide-field
integral field unit (IFU) data have been obtained, and are used to constrain
orbit-based dynamical models and stellar population synthesis (SPS) fits, to
unravel their structural and dynamical properties. We first show that our
galaxies are outliers in the present-day stellar mass-size relation. They are,
however, consistent with the mass-size relation of compact, massive and
quiescent galaxies at redshift z=2. The compact sizes of our nearby galaxies
imply high central stellar mass surface densities, which are also in agreement
with the massive galaxy population at higher redshift, hinting at strong
dissipational processes during their formation. Corroborating evidence for a
largely passive evolution within the last 10 Gyr is provided by their orbital
distribution as well as their stellar populations, which are difficult to
reconcile with a very active (major) merging history. This all supports that we
can use nearby CEGs as local analogues of the high-redshift, massive and
quiescent galaxy population, thus providing additional constraints for models
of galaxy formation and evolution.Comment: 33 pages, 27 figures and 20 tables (with most of the tables provided
as online-only supporting information). Accepted for publication in MNRA
Efficient Parametrization of the Vertex Function, -Scheme, and the (t,t')-Hubbard Model at Van Hove Filling
We propose a new parametrization of the four-point vertex function in the
one-loop one-particle irreducible renormalization group (RG) scheme for
fermions. It is based on a decomposition of the effective two-fermion
interaction into fermion bilinears that interact via exchange bosons. The
numerical computation of the RG flow of the boson propagators reproduces the
leading weak coupling instabilities of the two-dimensional Hubbard model at Van
Hove filling, as they were previously obtained by a temperature RG flow.
Instead of regularizing with temperature, we here use a soft frequency
-regularization that likewise does not artificially suppress
ferromagnetism. Besides being more efficient than previous N-patch schemes,
this parametrization also reduces the ambiguities in introducing boson fields.Comment: 33 pages, 11 figures, references adde
Palaearctic biogeography revisited: evidence for the existence of a North African refugium for Western Palaearctic biota
Aim: In contrast to the attention given to southern Europe both as a centre of
speciation and differentiation and as a Pleistocene refugium of Western Palae-
arctic taxa, North Africa has been relatively neglected. In this paper, we set out
to address this shortfall.
Location North-West Africa and the Mediterranean.
Methods We reviewed the existing literature on the biogeography of North
Africa, and carried out analyses of species distribution data using parsimony,
nestedness and co-occurrence methods.
Results In many cases, distribution patterns of non-flying mammals, bats,
amphibians, reptiles, butterflies, zygaenid moths and odonates demonstrated
important biogeographical affinities between Europe and North Africa at the
species level. On the other hand, species co-occurrence, nestedness and parsi-
mony analysis also revealed some deep splits between the Maghreb and Europe;
yet even in these cases the closest affinities were found between the Iberian
Peninsula and the Maghreb. Furthermore, North Africa harbours the highest
proportion of endemic taxa (13.7%) across all groups analysed. Many molecu-
lar studies demonstrated a strong genetic cohesiveness between North Africa
and Europe despite the potential barrier effect of the Mediterranean Sea. In
other taxa, however, remarkable splits were detected. In addition, southern
European genetic lineages were often nested within North African clades, and
many taxa showed exceptionally high genetic variability and differentiation in
this region.
Main conclusions The Maghreb was an important differentiation and specia-
tion centre for thermophilic organisms during the Pliocene and Pleistocene
with high relevance as a colonization source for Europe. The regions around
the sea straits of Gibraltar and Sicily have acted as important biogeographical
links between North Africa and Europe at different times
Resolving galaxies in time and space: II: Uncertainties in the spectral synthesis of datacubes
In a companion paper we have presented many products derived from the
application of the spectral synthesis code STARLIGHT to datacubes from the
CALIFA survey, including 2D maps of stellar population properties and 1D
averages in the temporal and spatial dimensions. Here we evaluate the
uncertainties in these products. Uncertainties due to noise and spectral shape
calibration errors and to the synthesis method are investigated by means of a
suite of simulations based on 1638 CALIFA spectra for NGC 2916, with
perturbations amplitudes gauged in terms of the expected errors. A separate
study was conducted to assess uncertainties related to the choice of
evolutionary synthesis models. We compare results obtained with the Bruzual &
Charlot models, a preliminary update of them, and a combination of spectra
derived from the Granada and MILES models. About 100k CALIFA spectra are used
in this comparison.
Noise and shape-related errors at the level expected for CALIFA propagate to
0.10-0.15 dex uncertainties in stellar masses, mean ages and metallicities.
Uncertainties in A_V increase from 0.06 mag in the case of random noise to 0.16
mag for shape errors. Higher order products such as SFHs are more uncertain,
but still relatively stable. Due to the large number statistics of datacubes,
spatial averaging reduces uncertainties while preserving information on the
history and structure of stellar populations. Radial profiles of global
properties, as well as SFHs averaged over different regions are much more
stable than for individual spaxels. Uncertainties related to the choice of base
models are larger than those associated with data and method. Differences in
mean age, mass and metallicity are ~ 0.15 to 0.25 dex, and 0.1 mag in A_V.
Spectral residuals are ~ 1% on average, but with systematic features of up to
4%. The origin of these features is discussed. (Abridged)Comment: A&A, accepte
The dependence of oxygen and nitrogen abundances on stellar mass from the CALIFA survey
We analysed the optical spectra of HII regions extracted from a sample of 350
galaxies of the CALIFA survey. We calculated total O/H abundances and, for the
first time, N/O ratios using the semi-empirical routine HII-CHI-mistry, which,
according to P\'erez-Montero (2014), is consistent with the direct method and
reduces the uncertainty in the O/H derivation using [NII] lines owing to the
dispersion in the O/H-N/O relation. Then we performed linear fittings to the
abundances as a function of the de-projected galactocentric distances. The
analysis of the radial distribution both for O/H and N/O in the non-interacting
galaxies reveals that both average slopes are negative, but a non-negligible
fraction of objects have a flat or even a positive gradient (at least 10\% for
O/H and 4\% for N/O). The slopes normalised to the effective radius appear to
have a slight dependence on the total stellar mass and the morphological type,
as late low-mass objects tend to have flatter slopes. No clear relation is
found, however, to explain the presence of inverted gradients in this sample,
and there is no dependence between the average slopes and the presence of a
bar. The relation between the resulting O/H and N/O linear fittings at the
effective radius is much tighter (correlation coefficient = 0.80) than
between O/H and N/O slopes ( = 0.39) or for O/H and N/O in the
individual \hii\ regions ( = 0.37). These O/H and N/O values at the
effective radius also correlate very tightly (less than 0.03 dex of dispersion)
with total luminosity and stellar mass. The relation with other integrated
properties, such as star formation rate, colour, or morphology, can be
understood only in light of the found relation with mass.Comment: Accepted for publication in A&A. 20 pages, 19 figure
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