128 research outputs found
Spectroscopy of Giant Stars in the Pyxis Globular Cluster
The Pyxis globular cluster is a recently discovered globular cluster that
lies in the outer halo (R_{gc} ~ 40 kpc) of the Milky Way. Pyxis lies along one
of the proposed orbital planes of the Large Magellanic Cloud (LMC), and it has
been proposed to be a detached LMC globular cluster captured by the Milky Way.
We present the first measurement of the radial velocity of the Pyxis globular
cluster based on spectra of six Pyxis giant stars. The mean heliocentric radial
velocity is ~ 36 km/sec, and the corresponding velocity of Pyxis with respect
to a stationary observer at the position of the Sun is ~ -191 km/sec. This
radial velocity is a large enough fraction of the cluster's expected total
space velocity, assuming that it is bound to the Milky Way, that it allows
strict limits to be placed on the range of permissible transverse velocities
that Pyxis could have in the case that it still shares or nearly shares an
orbital pole with the LMC. We can rule out that Pyxis is on a near circular
orbit if it is Magellanic debris, but we cannot rule out an eccentric orbit
associated with the LMC. We have calculated the range of allowed proper motions
for the Pyxis globular cluster that result in the cluster having an orbital
pole within 15 degrees of the present orbital pole of the LMC and that are
consistent with our measured radial velocity, but verification of the tidal
capture hypothesis must await proper motion measurement from the Space
Interferometry Mission or HST. A spectroscopic metallicity estimate of [Fe/H] =
-1.4 +/- 0.1 is determined for Pyxis from several spectra of its brightest
giant; this is consistent with photometric determinations of the cluster
metallicity from isochrone fitting.Comment: 22 pages, 5 figures, aaspp4 style, accepted for publication in
October, 2000 issue of the PAS
Interleukin-33 contributes to both M1 and M2 chemokine marker expression in human macrophages
Abstract Background Interleukin-33 is a member of the IL-1 cytokine family whose functions are mediated and modulated by the ST2 receptor. IL-33-ST2 expression and interactions have been explored in mouse macrophages but little is known about the effect of IL-33 on human macrophages. The expression of ST2 transcript and protein levels, and IL-33-mediated effects on M1 (i.e. classical activation) and M2 (i.e. alternative activation) chemokine marker expression in human bone marrow-derived macrophages were examined. Results Human macrophages constitutively expressed the membrane-associated (i.e. ST2L) and the soluble (i.e. sST2) ST2 receptors. M2 (IL-4 + IL-13) skewing stimuli markedly increased the expression of ST2L, but neither polarizing cytokine treatment promoted the release of sST2 from these cells. When added to naïve macrophages alone, IL-33 directly enhanced the expression of CCL3. In combination with LPS, IL-33 blocked the expression of the M2 chemokine marker CCL18, but did not alter CCL3 expression in these naive cells. The addition of IL-33 to M1 macrophages markedly increased the expression of CCL18 above that detected in untreated M1 macrophages. Similarly, alternatively activated human macrophages treated with IL-33 exhibited enhanced expression of CCL18 and the M2 marker mannose receptor above that detected in M2 macrophages alone. Conclusions Together, these data suggest that primary responses to IL-33 in bone marrow derived human macrophages favors M1 chemokine generation while its addition to polarized human macrophages promotes or amplifies M2 chemokine expression.http://deepblue.lib.umich.edu/bitstream/2027.42/78250/1/1471-2172-11-52.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78250/2/1471-2172-11-52.pdfPeer Reviewe
Absolute Proper Motion of the Fornax Dwarf Spheroidal Galaxy from Photographic and HST WFPC2 Data
We have measured the absolute proper motion of the Fornax dwarf spheroidal
galaxy from a combination of photographic plate material and HST WFPC2 data
that provide a time baseline of up to 50 years. The extragalactic reference
frame consists of 8 QSO images and 48 galaxies. The absolute proper motion is
mu_alpha cos(delta) = 0.59 +-0.16 mas/yr and mu_delta = -0.15 +- 0.16 mas/yr.
The corresponding orbit of Fornax is polar, with an eccentricity of 0.27, and a
radial period of 4.5 Gyr. Fornax's current location is near pericenter. The
direction of the motion of Fornax supports the notion that Fornax belongs to
the Fornax-LeoI-LeoII-Sculptor-Sextans stream as hypothesized by Lynden-Bell
(1976, 1982) and Majewski (1994).
According to our orbit determination, Fornax crossed the Magellanic plane
\~190 Myr ago, a time that coincides with the termination of the star-formation
process in Fornax. We propose that ram-pressure stripping due to the passage of
Fornax through a gaseous medium denser than the typical intragalactic medium
left behind from the LMC may have caused the end of star formation in Fornax.
The excess, anomalous clouds within the South Galactic pole region of the
Magellanic Stream whose origin has long been debated in the literature as
constituents of either the Magellanic Stream or of the extragalactic Sculptor
group, are found to lie along the orbit of Fornax. We speculate that these
clouds are stripped material from Fornax as the dwarf crossed the Magellanic
Clouds' orbit.Comment: Accepted for publication in Astronomical Journal. The version with
high resolution figures can be found at
ftp://pegasus.astro.yale.edu/pub/dana/paper
A systemic granulomatous response to Schistosoma mansoni eggs alters responsiveness of bone marrowâderived macrophages to Tollâlike receptor agonists
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141008/1/jlb0314.pd
Chemokine and inflammatory cytokine changes during chronic wound healing
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75761/1/j.1524-475X.1997.50405.x.pd
Orbits of Globular Clusters in the Outer Galaxy: NGC 7006
We present a proper motion study of the distant globular cluster NGC 7006
based on the measurement of 25 photographic plates spanning a 40-year interval.
The absolute proper motion determined with respect to extragalactic objects is
(-0.96, -1.14) +- (0.35, 0.40) mas/yr. The total space velocity of NGC 7006 in
a Galactocentric rest frame is 279 km/s, placing the cluster on one of the most
energetic orbits (Ra =102 kpc) known to date for clusters within 40-kpc from
the Galactic center. We compare the orbits of four clusters that have
apocentric radii larger than 80 kpc (NGC 5466, NGC 6934, NGC 7006 and Pal 13)
with those of Galactic satellites with well-measured proper motions. These
clusters have orbits that are highly eccentric and of various inclinations with
respect to the Galactic plane. In contrast, the orbits of the Galactic
satellites are of low to moderate eccentricity and highly inclined. Based on
orbit types, chemical abundances and cluster parameters, we discuss the
properties of the hypothetical host systems of the remote globular clusters in
the Searle-Zinn paradigm. It is apparent that clusters such as NGC 5466, NGC
6934 and NGC 7006 formed in systems that more likely resemble the Fornax dSph,
rather than the Sagittarius dSph. We also discuss plausible causes for the
difference found so far between the orbit type of outer halo clusters and that
of Galactic satellites and for the tentative, yet suggestive phase-space
scatter found among outer halo clusters.Comment: 27 pages, 5 figures, to be published in the Astronomical Journa
Mast cells produce ENAâ78, which can function as a potent neutrophil chemoattractant during allergic airway inflammation
The inflammatory response during allergic airway inflammation involves the recruitment of multiple leukocyte populations, including neutrophils, monocytes, lymphocytes, and eosinophils. All of these populations likely contribute to the pathology observed during repeated episodes of allergic airway inflammation. We have examined the role of a human neutrophilâspecific chemokine (CâxâC), ENAâ78, in a model of allergic airway responses and identified murine mast cells as a cellular source of an ENAâ78âlike molecule. Within this allergic airway model, neutrophil infiltration into the airway occurs within 4â8 h postâallergen challenge, persists within the airway until 24 h, and resolves by 48 h postâchallenge. Neutrophil influx precedes the eosinophil infiltration, which peaks in the airway at 48 h postâallergen challenge. In this study the production of ENAâ78 from challenged lungs demonstrated a significant increase in the allergenâ,but not vehicleâ, challenged lungs. In vivo neutralization of ENAâ78 by passive immunization demonstrated a significant decrease in peak neutrophil infiltration at 8 h, with no effect on the eosinophil infiltration at 48 h postâchallenge. Because ENAâ78 has been shown to be chemotactic for neutrophils and given the involvement of mast cell degranulation in allergic responses, we examined mast cells for the presence of ENAâ78. Cultured mast cells spontaneously released ENAâ78, but on activation with IgE + antigen, NGâLâarginine methyl ester or compound 48/80 produced significantly increased levels of ENAâ78. Supernatants from sonicated MCâ9 mast cells induced an overwhelming influx of neutrophils into the BAL by 4 h postâintratracheal injection into mice, suggesting that the mast cell is a significant source of neutrophil chemotactic factors. Mast cell supernatantâmediated neutrophil infiltration was substantially decreased by preincubation of the supernatant with antibodies specific for ENAâ78. These data indicate a major neutrophil chemotactic protein produced by mast cells during allergic responses may be mast cellâderived ENAâ78. J. Leukoc. Biol. 63: 746â751; 1998.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141710/1/jlb0746.pd
Exploring Halo Substructure with Giant Stars. VI. Extended Distributions of Giant Stars Around the Carina Dwarf Spheroidal Galaxy -- How Reliable Are They?
The question of the existence of active tidal disruption around various dSph
galaxies remains controversial. That debate often centers on the nature (bound
vs. unbound) of extended populations of stars. However, the more fundamental
issue of the very existence of the extended populations is still contentious.
We present an evaluation of the debate centering on one particular dSph,
Carina, for which claims both for and against the existence of stars beyond the
King radius have been made. Our review includes an examination of all previous
studies bearing on the Carina radial profile and shows that the survey method
which achieves the highest detected dSph signal-to-background in the outer
parts of the galaxy is the Washington M, T2 + DDO51 (MTD) filter approach from
Paper II in this series. We then address statistical methods used to evaluate
the reliability of MTD surveys in the presence of photometric errors and for
which a new, a posteriori statistical analysis methodology is provided.
Finally, these statistical methods are tested by new spectroscopy of stars in
the MTD-selected Carina candidate sample. Of 74 candidate giants with follow-up
spectroscopy, the MTD technique identified 61 new Carina members, including 8
stars outside the King radius. From a sample of 29 stars not initially
identified as candidate Carina giants but that lie just outside of our
selection criteria, 12 have radial velocities consistent with membership,
including 5 extratidal stars. Carina is shown to have an extended population of
giant stars extending to a major axis radius of 40' (1.44x the nominal King
radius).Comment: 56 pages, 10 figures. Submitted to the Astronomical Journal, 2004 Sep
2
A Two Micron All-Sky Survey View of the Sagittarius Dwarf Galaxy: II. Swope Telescope Spectroscopy of M Giant Stars in the Dynamically Cold Sagittarius Tidal Stream
We present moderate resolution (~6 km/s) spectroscopy of 284 M giant
candidates selected from the Two Micron All Sky Survey photometry. Radial
velocities (RVs) are presented for stars mainly in the south, with a number
having positions consistent with association to the trailing tidal tail of the
Sagittarius (Sgr) dwarf galaxy. The latter show a clear RV trend with orbital
longitude, as expected from models of the orbit and destruction of Sgr. A
minimum 8 kpc width of the trailing stream about the Sgr orbital midplane is
implied by verified RV members. The coldness of this stream (dispersion ~10
km/s) provides upper limits on the combined contributions of stream heating by
a lumpy Galactic halo and the intrinsic dispersion of released stars, which is
a function of the Sgr core mass. The Sgr trailing arm is consistent with a
Galactic halo containing one dominant, LMC-like lump, however some lumpier
halos are not ruled out. An upper limit to the total M/L of the Sgr core is 21
in solar units. A second structure that roughly mimics expectations for
wrapped, leading Sgr arm debris crosses the trailing arm in the Southern
Hemisphere; however, this may also be an unrelated tidal feature. Among the <13
kpc M giants toward the South Galactic Pole are some with large RVs that
identify them as halo stars, perhaps part of the Sgr leading arm near the Sun.
The positions and RVs of Southern Hemisphere M giants are compared with those
of southern globular clusters potentially stripped from the Sgr system and
support for association of Pal 2 and Pal 12 with Sgr debris is found. Our
discussion includes description of a masked-filtered cross-correlation
methodology that achieves better than 1/20 of a resolution element RVs in
moderate resolution spectra.Comment: 41 pages, 6 figures, Astronomical Journal, in press (submitted Nov.
24, 2003; tentatively scheduled for July 2004 issue
- âŠ