3,266 research outputs found
Wide-Field Survey of Globular Clusters in M31. II. Kinematics of the Globular Cluster System
We present a kinematic analysis of the globular cluster(GC) system in M31.
Using the photometric and spectroscopic database of 504 GCs, we have
investigated the kinematics of the M31 GC system. We find that the all GC
system shows strong rotation, with rotation amplitude of v_rot~190km/s, and
that a weak rotation persists even for the outermost samples at |Y|>5kpc. The
rotation-corrected velocity dispersion for the GC system is estimated to be
sigma_{p,r}~130km/s, and it increases from sigma_{p,r}~120km/s at |Y|<1kpc to
sigma_{p,r}~150km/s at |Y|>5kpc. These results are very similar to those for
the metal-poor GCs. This shows that there is a dynamically hot halo in M31 that
is rotating but primarily pressure-supported. We have identified 50
"friendless" GCs, and they appear to rotate around the major axis of M31. For
the subsamples of metal-poor and metal-rich GCs, we have found that the
metal-rich GCs are more centrally concentrated than the metal-poor GCs, and
both subsamples show strong rotation. For the subsamples of bright and faint
GCs, it is found that the rotation for the faint GCs is stronger than that for
the bright GCs. We have identified 56 GCs and GC candidates with X-ray
detection. It is found that the majority of X-ray emitting GCs follow the disk
rotation, and that the redder, more metal-rich, and brighter GCs are more
likely to be detected as X-ray emitting GCs. We have derived a rotation curve
of M31 using the GCs at |Y|<0.6kpc. We have estimated the dynamical mass of M31
using `Projected Mass Estimator(PME)' and `Tracer Mass Estimator(TME)'. We
finally discuss the implication of these results and compare the kinematics of
GCs with that of planetary nebulae in M31.Comment: 62 pages, 26 figues, Accepted by Ap
Washington CCD Photometry of the Globular Cluster System of the Giant Elliptical Galaxy M60 in Virgo
We present a photometric study of the globular clusters in the giant
elliptical galaxy M60 in the Virgo cluster, based on deep, relatively wide
field Washington CT_1 CCD images. The color-magnitude diagram reveals a
significant population of globular clusters in M60, and a large number of young
luminous clusters in NGC 4647, a small companion spiral galaxy north-west of
M60. The color distribution of the globular clusters in M60 is clearly bimodal,
with a blue peak at (C-T_1)=1.37, and a red peak at (C-T_1)=1.87. We derive two
new transformation relations between the (C-T_1)_0 color and [Fe/H] using the
data for the globular clusters in our Galaxy and M49. Using these relations we
derive the metallicity distribution of the globular clusters in M60, which is
also bimodal: a dominant metal-poor component with center at [Fe/H]=-1.2, and a
weaker metal-rich component with center at [Fe/H]=-0.2. The radial number
density profile of the globular clusters is more extended than that of the
stellar halo, and the radial number density profile of the blue globular
clusters is more extended than that of the red globular clusters. The number
density maps of the globular clusters show that the spatial distribution of the
blue globular clusters is roughly circular, while that of the red globular
cluster is elongated similarly to that of the stellar halo. We estimate the
total number of the globular clusters in M60 to be 3600+/-500$,and the specific
frequency to be S_N=3.8+/-0.4. The mean color of the bright blue globular
clusters gets redder as they get brighter in both the inner and outer region of
M60. This blue tilt is seen also in the outer region of M49, the brightest
Virgo galaxy. Implications of these results are discussed.Comment: 32 pages, 22 figues, Accepted by Ap
Wide-Field Survey of Globular Clusters in M31. I. A Catalog of New Clusters
We present the result of a wide-field survey of globular clusters (GCs) in
M31 covering a 3deg x 3deg field c. We have searched for GCs on CCD images
taken with Washington CMT1 filters at the KPNO 0.9 m telescope using steps: (1)
inspection of morphological parameters given by the SExtractor package such as
stellarity, full maximum, and ellipticity; (2) consulting the spectral types
and radial velocities obtained from spectra takena spectrograph at the WIYN 3.5
m telescope; and (3) visual inspection of the images of each object. We have
and GC candidates, of which 605 are newly found GCs and GC candidates and 559
are previously known GCs. Amoects there are 113 genuine GCs, 258 probable GCs,
and 234 possible GCs, according to our classification critee known objects
there are 383 genuine GCs, 109 probable GCs, and 67 possible GCs. In total
there are 496 genprobable GCs and 301 possible GCs. Most of these newly found
GCs have T1 magnitudes of 17.5 - 19.5 mag, [17.9 < V < 19.9 mag assuming (C-T1)
~ 1.5], and (C-T1) colors in the range 1 - 2.Comment: accepted by AJ, using emulateapj.cl
Dynamics of the Globular Cluster System Associated with M87 (NGC 4486). II. Analysis
We present a dynamical analysis of the globular cluster system associated
with M87 (= NGC 4486), the cD galaxy near the dynamical center of the Virgo
cluster. The analysis utilizes a new spectroscopic and photometric database
which is described in a companion paper (Hanes et al. 2001). Using a sample of
278 globular clusters with measured radial velocities and metallicities, and
new surface density profiles based on wide-field Washington photometry, we
study the dynamics of the M87 globular cluster system both globally --- for the
entire cluster sample --- and separately --- for the metal-rich and metal-poor
globular cluster samples. This constitutes the largest sample of radial
velocities for pure Population II tracers yet assembled for any galaxy. We
discuss the implications of our findings for models for the formation of giant
elliptical galaxies, globular cluster systems, and the Virgo cluster.
(ABRIDGED)Comment: 28 pages, 19 postscript figures, 1 jpeg image. See
http://www.physics.rutgers.edu/ast/ast-rap.html to download the manuscript
with higher quality figures. Accepted for publication in the Astrophysical
Journa
phot1 inhibition of ABCB19 primes lateral auxin fluxes in the shoot apex required for phototropism
It is well accepted that lateral redistribution of the phytohormone auxin underlies the bending of plant organs towards light. In monocots, photoreception occurs at the shoot tip above the region of differential growth. Despite more than a century of research, it is still unresolved how light regulates auxin distribution and where this occurs in dicots. Here, we establish a system in Arabidopsis thaliana to study hypocotyl phototropism in the absence of developmental events associated with seedling photomorphogenesis. We show that auxin redistribution to the epidermal sites of action occurs at and above the hypocotyl apex, not at the elongation zone. Within this region, we identify the auxin efflux transporter ATP-BINDING CASSETTE B19 (ABCB19) as a substrate target for the photoreceptor kinase PHOTOTROPIN 1 (phot1). Heterologous expression and physiological analyses indicate that phosphorylation of ABCB19 by phot1 inhibits its efflux activity, thereby increasing auxin levels in and above the hypocotyl apex to halt vertical growth and prime lateral fluxes that are subsequently channeled to the elongation zone by PIN-FORMED 3 (PIN3). Together, these results provide new insights into the roles of ABCB19 and PIN3 in establishing phototropic curvatures and demonstrate that the proximity of light perception and differential phototropic growth is conserved in angiosperm
The Predominant CD4+ Th1 Cytokine Elicited to Chlamydia trachomatis Infection in Women Is Tumor Necrosis Factor Alpha and Not Interferon Gamma
Chlamydia trachomatis infection is the most prevalent bacterial sexually transmitted infection and can cause significant reproductive morbidity in women. There is insufficient knowledge of C. trachomatis-specific immune responses in humans, which could be important in guiding vaccine development efforts. In contrast, murine models have clearly demonstrated the essential role of T helper type 1 (Th1) cells, especially interferon gamma (IFN-γ)-producing CD4+ T cells, in protective immunity to chlamydia. To determine the frequency and magnitude of Th1 cytokine responses elicited to C. trachomatis infection in humans, we stimulated peripheral blood mononuclear cells from 90 chlamydia-infected women with C. trachomatis elementary bodies, Pgp3, and major outer membrane protein and measured IFN-γ-, tumor necrosis factor alpha (TNF-α)-, and interleukin-2 (IL-2)-producing CD4+ and CD8+ T-cell responses using intracellular cytokine staining. The majority of chlamydia-infected women elicited CD4+ TNF-α responses, with frequency and magnitude varying significantly depending on the C. trachomatis antigen used. CD4+ IFN-γ and IL-2 responses occurred infrequently, as did production of any of the three cytokines by CD8+ T cells. About one-third of TNF-α-producing CD4+ T cells coproduced IFN-γ or IL-2. In summary, the predominant Th1 cytokine response elicited to C. trachomatis infection in women was a CD4+ TNF-α response, not CD4+ IFN-γ, and a subset of the CD4+ TNF-α-positive cells produced a second Th1 cytokine
Broad activation of the ubiquitin-proteasome system by Parkin is critical for mitophagy
Parkin, an E3 ubiquitin ligase implicated in Parkinson's disease, promotes degradation of dysfunctional mitochondria by autophagy. Using proteomic and cellular approaches, we show that upon translocation to mitochondria, Parkin activates the ubiquitin–proteasome system (UPS) for widespread degradation of outer membrane proteins. This is evidenced by an increase in K48-linked polyubiquitin on mitochondria, recruitment of the 26S proteasome and rapid degradation of multiple outer membrane proteins. The degradation of proteins by the UPS occurs independently of the autophagy pathway, and inhibition of the 26S proteasome completely abrogates Parkin-mediated mitophagy in HeLa, SH-SY5Y and mouse cells. Although the mitofusins Mfn1 and Mfn2 are rapid degradation targets of Parkin, we find that degradation of additional targets is essential for mitophagy. These results indicate that remodeling of the mitochondrial outer membrane proteome is important for mitophagy, and reveal a causal link between the UPS and autophagy, the major pathways for degradation of intracellular substrates
Effects of elevated root zone CO2 and air temperature on photosynthetic gas exchange, nitrate uptake, and total reduced nitrogen content in aeroponically grown lettuce plants
Effects of elevated root zone (RZ) CO2 and air temperature on photosynthesis, productivity, nitrate (NO3–), and total reduced nitrogen (N) content in aeroponically grown lettuce plants were studied. Three weeks after transplanting, four different RZ [CO2] concentrations [ambient (360 ppm) and elevated concentrations of 2000, 10 000, and 50 000 ppm] were imposed on plants grown at two air temperature regimes of 28 °C/22 °C (day/night) and 36 °C/30 °C. Photosynthetic CO2 assimilation (A) and stomatal conductance (gs) increased with increasing photosynthetically active radiation (PAR). When grown at 28 °C/22 °C, all plants accumulated more biomass than at 36 °C/30 °C. When measured under a PAR ≥600 μmol m−2 s−1, elevated RZ [CO2] resulted in significantly higher A, lower gs, and higher midday leaf relative water content in all plants. Under elevated RZ [CO2], the increase of biomass was greater in roots than in shoots, causing a lower shoot/root ratio. The percentage increase in growth under elevated RZ [CO2] was greater at 36 °C/30 °C although the total biomass was higher at 28 °C/22 °C. NO3– and total reduced N concentrations of shoot and root were significantly higher in all plants under elevated RZ [CO2] than under ambient RZ [CO2] of 360 ppm at both temperature regimes. At each RZ [CO2], NO3– and total reduced N concentration of shoots were greater at 28 °C/22 °C than at 36 °C/30 °C. At all RZ [CO2], roots of plants at 36 °C/30 °C had significantly higher NO3– and total reduced N concentrations than at 28 °C/22 °C. Since increased RZ [CO2] caused partial stomatal closure, maximal A and maximal gs were negatively correlated, with a unique relationship for each air temperature. However, across all RZ [CO2] and temperature treatments, there was a close correlation between maximal A and total shoot reduced N concentration of plants under different RZ [CO2], indicating that increased A under elevated RZ [CO2] could partially be due to the higher shoot total reduced N
Radial Velocity and Metallicity of the Globular Cluster IC4499 Obtained with AAOmega
We present radial velocity and metallicity measurements for the far-southern
Galactic globular cluster IC4499. We selected several hundred target red giant
stars in and around the cluster from the 2MASS point source catalog, and
obtained spectra at the near-infrared calcium triplet using the AAOmega
spectrograph. Observations of giants in globular clusters M4, M22, and M68 were
taken to provide radial velocity and metallicity comparison objects. Based on
velocity data we conclude that 43 of our targets are cluster members, by far
the largest sample of IC4499 giants spectroscopically studied. We determine the
mean heliocentric radial velocity of the cluster to be 31.5 plus or minus 0.4
km/s, and find the most likely central velocity dispersion to be 2.5 plus or
minus 0.5 km/s. This leads to a dynamical mass estimate for the cluster of 93
plus or minus 37 thousand solar masses. We are sensitive to cluster rotation
down to an amplitude of about 1 km/s, but no evidence for cluster rotation is
seen. The cluster metallicity is found to be [Fe/H] = -1.52 plus or minus 0.12
on the Carretta-Gratton scale. The radial velocity of the cluster, previously
highly uncertain, is consistent with membership in the Monoceros tidal stream,
but also with a halo origin. The horizontal branch morphology of the cluster is
slightly redder than average for its metallicity, but it is likely not
unusually young compared to other clusters of the halo. The new constraints on
the cluster kinematics and metallicity may give insight into its extremely high
specific frequency of RR Lyrae stars.Comment: Accepted to MNRAS, 13 pages, 9 figure
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