235 research outputs found
A Study of Cepheids in M81 with the Large Binocular Telescope (Efficiently Calibrated with HST)
We identify and phase a sample of 107 Cepheids with 10<P/days<100 in M81
using the LBT and calibrate their BVI mean magnitudes with archival HST data.
The use of a ground-based telescope to identify and phase the Cepheids and HST
only for the final calibration reduces the demand on HST by nearly an order of
magnitude and yields Period-Luminosity (PL) relations with dispersions
comparable to the best LMC samples. We fit the sample using the OGLE-II LMC PL
relations and are unable to find a self-consistent distance for different band
combinations or radial locations within M81. We can do so after adding a radial
dependence to the PL zero point that corresponds to a luminosity dependence on
metallicity of g_mu=-0.56+/-0.36 mag/dex. We find marginal evidence for a shift
in color as a function of metallicity, distinguishable from the effects of
extinction, of g_2=+0.07+/-0.03 mag/dex. We find a distance modulus for M81,
relative to the LMC, of mu(M81-LMC)=9.39+/-0.14 mag, including uncertainties
due to the metallicity corrections. This corresponds to a distance to M81 of
3.6+/-0.2 Mpc, assuming a LMC distance modulus of 18.41 mag. We carry out a
joint analysis of M81 and NGC4258 Cepheids and simultaneously solve for the
distance of M81 relative to NGC4258 and the metallicity corrections. Given the
current data, the uncertainties of such joint fits are dominated by the
relative metallicities and the abundance gradients rather than by measurement
errors of the Cepheid magnitudes or colors. We find mu(M81-LMC)=9.40
(-0.11/+0.15) mag, mu(N4258-LMC)=11.08 (-0.17/+0.21) mag and
mu(N4258-M81)=1.68+/-0.08 mag and joint metallicity corrections of g_mu=-0.62
(-0.35/+0.31) mag/dex and g_2=0.01+/-0.01 mag/dex. Quantitative analyses of
Cepheid distances must take into account both the metallicity dependencies of
the Cepheids and the uncertainties in the abundance estimates. (ABRIDGED)Comment: 45 pages, 14 figures, 4 tables, appeared in The Astrophysical Journa
Using Continuous Data Tracking Technology to Study Exercise Adherence in Pulmonary Rehabilitation
Pulmonary rehabilitation is widely recognized in the management of respiratory diseases. A key component to successful pulmonary rehabilitation is adherence to the recommended exercise training. The purpose of the present protocol is to describe how continuous data tracking technology can be used to precisely measure adherence to a prescribed aerobic training intensity
An improved method for statistical studies of the internal kinematics of HII regions: the case of M 83
We present the integrated Halpha emission line profile for 157 HII regions in
the central 3.4' x 3.4' of the galaxy M 83 (NGC 5236). Using the Fabry-Perot
interferometer GHaFaS, on the 4.2 m William Herschel on La Palma, we show the
importance of a good characterization of the instrumental response function for
the study of line profile shapes. The luminosity-velocity dispersion relation
is also studied, and in the log(L)-log(sigma) plane we do not find a linear
relation, but an upper envelope with equation log(L)=0.9 *log(sigma)+38.1. For
the adopted distance of 4.5 Mpc, the upper envelope appears at the luminosity
L=10^38.5 ergs, in full agreement with previous studies of other galaxies,
reinforcing the idea of using HII regions as standard candles.Comment: 13 pages, 9 figures, accepted for publication in MNRA
The central region of M83: Massive star formation, kinematics, and the location and origin of the nucleus
We report new near-IR integral field spectroscopy of the central starburst
region of the barred spiral galaxy M83 obtained with CIRPASS on Gemini-S, which
we analyse in conjunction with GHaFaS Fabry-Perot data, an AAT IRIS2 Ks-band
image, and near- and mid-IR imaging from the Hubble and Spitzer space
telescopes. The bulk of the current star formation activity is hidden from
optical view by dust extinction, but is seen in the near- and mid-IR to the
north of the nucleus. This region is being fed by inflow of gas through the bar
of M83, traced by the prominent dust lane entering into the circumnuclear
region from the north. An analysis of stellar ages confirms that the youngest
stars are indeed in the northwest. A gradual age gradient, with older stars
further to the south, characterises the well-known star-forming arc in the
central region of M83. Detailed analyses of the Pa beta ionised gas kinematics
and near-IR imaging confirm that the kinematic centre coincides with the
photometric centre of M83, and that these are offset significantly, by about 3
arcsec or 60 pc, from the visible nucleus of the galaxy. We discuss two
possible options, the first of which postulates that the kinematic and
photometric centre traces a galaxy nucleus hidden by a substantial amount of
dust extinction, in the range A_V=3-10 mag. By combining this information with
kinematic results and using arguments from the literature, we conclude that
such a scenario is, however, unlikely, as is the existence of other "hidden"
nuclei in M83. We thus concur with recent authors and favour a second option,
in which the nucleus of the galaxy is offset from its kinematic and photometric
centre. This is presumably a result of some past interaction, possibly related
to the event which lies at the origin of the disturbance of the outer disk of
the galaxy. (Abridged)Comment: MNRAS, in press; 16 pages latex, 15 figure
Novel insights into the cardio-protective effects of FGF21 in lean and obese rat hearts
Aims: Fibroblast growth factor 21 (FGF21) is a hepatic metabolic regulator with pleotropic actions. Its plasma concentrations are increased in obesity and diabetes; states associated with an increased incidence of cardiovascular disease. We therefore investigated the direct effect of FGF21 on cardio-protection in obese and lean hearts in response to ischemia.
Methods and Results: FGF21, FGF21-receptor 1 (FGFR1) and beta-Klotho (βKlotho) were expressed in rodent, human hearts and primary rat cardiomyocytes. Cardiac FGF21 was expressed and secreted (real time RT-PCR/western blot and ELISA) in an autocrine-paracrine manner, in response to obesity and hypoxia, involving FGFR1-βKlotho components. Cardiac-FGF21 expression and secretion were increased in response to global ischemia. In contrast βKlotho was reduced in obese hearts. In isolated adult rat cardiomyocytes, FGF21 activated PI3K/Akt (phosphatidylinositol 3-kinase/Akt), ERK1/2(extracellular signal-regulated kinase) and AMPK (AMP-activated protein kinase) pathways. In Langendorff perfused rat [adult male wild-type wistar] hearts, FGF21 administration induced significant cardio-protection and restoration of function following global ischemia. Inhibition of PI3K/Akt, AMPK, ERK1/2 and ROR-α (retinoic-acid receptor alpha) pathway led to significant decrease of FGF21 induced cardio-protection and restoration of cardiac function in response to global ischemia. More importantly, this cardio-protective response induced by FGF21 was reduced in obesity, although the cardiac expression profiles and circulating FGF21 levels were increased.
Conclusion: In an ex vivo Langendorff system, we show that FGF21 induced cardiac protection and restoration of cardiac function involving autocrine-paracrine pathways, with reduced effect in obesity. Collectively, our findings provide novel insights into FGF21-induced cardiac effects in obesity and ischemia
Measuring the mass of the central black hole in the bulgeless galaxy ngc 4395 from gas dynamical modeling
NGC 4395 is a bulgeless spiral galaxy, harboring one of the nearest known type 1 Seyfert nuclei. Although there is no consensus on the mass of its central engine, several estimates suggest it is one of the lightest massive black holes (MBHs) known. We present the first direct dynamical measurement of the mass of this MBH from a combination of two-dimensional gas kinematic data, obtained with the adaptive optics assisted near-infrared integral field spectrograph Gemini/NIFS and high-resolution multiband photometric data from Hubble Space Telescope's Wide Field Camera 3. We use the photometric data to model the shape and stellar mass-to-light ratio of the nuclear star cluster (NSC). From the Gemini/NIFS observations, we derive the kinematics of warm molecular hydrogen gas as traced by emission through the H2 1–0 S(1) transition. These kinematics show a clear rotational signal, with a position angle orthogonal to NGC 4395's radio jet. Our best-fitting tilted ring models of the kinematics of the molecular hydrogen gas contain a black hole with mass M={4}-3+8× {10}5 M⊙ (3σ uncertainties) embedded in an NSC of mass M=2× {10}6 M⊙. Our black hole mass measurement is in excellent agreement with the reverberation mapping mass estimate of Peterson et al. but shows some tension with other mass measurement methods based on accretion signals
Reduced EPO receptor expression may contribute to limited pleiotropic effects of EPO during critical illness
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