45 research outputs found
Infrared Emission from the Nearby Cool Core Cluster Abell 2597
We observed the brightest central galaxy (BCG) in the nearby (z=0.0821) cool
core galaxy cluster Abell 2597 with the IRAC and MIPS instruments on board the
Spitzer Space Telescope. The BCG was clearly detected in all Spitzer
bandpasses, including the 70 and 160 micron wavebands. We report aperture
photometry of the BCG. The spectral energy distribution exhibits a clear excess
in the FIR over a Rayleigh-Jeans stellar tail, indicating a star formation rate
of ~4-5 solar masses per year, consistent with the estimates from the UV and
its H-alpha luminosity. This large FIR luminosity is consistent with that of a
starburst or a Luminous Infrared Galaxy (LIRG), but together with a very
massive and old population of stars that dominate the energy output of the
galaxy. If the dust is at one temperature, the ratio of 70 to 160 micron fluxes
indicate that the dust emitting mid-IR in this source is somewhat hotter than
the dust emitting mid-IR in two BCGs at higher-redshift (z~0.2-0.3) and higher
FIR luminosities observed earlier by Spitzer, in clusters Abell 1835 and Zwicky
3146.Comment: Accepted at Ap
Two Clusters with Radio-quiet Cooling Cores
Radio lobes inflated by active galactic nuclei at the centers of clusters are
a promising candidate for halting condensation in clusters with short central
cooling times because they are common in such clusters. In order to test the
AGN-heating hypothesis, we obtained Chandra observations of two clusters with
short central cooling times yet no evidence for AGN activity: Abell 1650 and
Abell 2244. The cores of these clusters indeed appear systematically different
from cores with more prominent radio emission. They do not have significant
central temperature gradients, and their central entropy levels are markedly
higher than in clusters with stronger radio emission, corresponding to central
cooling times ~ 1 Gigayear. Also, there is no evidence for fossil X-ray
cavities produced by an earlier episode of AGN heating. We suggest that either
(1) the central gas has not yet cooled to the point at which feedback is
necessary to prevent it from condensing, possibly because it is conductively
stabilized, or (2) the gas experienced a major heating event Gyr in
the past and has not required feedback since then. The fact that these clusters
with no evident feedback have higher central entropy and therefore longer
central cooling times than clusters with obvious AGN feedback strongly suggests
that AGNs supply the feedback necessary to suppress condensation in clusters
with short central cooling times.Comment: ApJ Letter, in pres
Two Clusters of Galaxies with Radio-quiet Cooling Cores
Radio lobes inflated by active galactic nuclei at the centers of clusters are a promising candidate for halting condensation in clusters with short central cooling times because they are common in such clusters. In order to test the AGNheating hypothesis, we obtained Chandra observations of two clusters with short central cooling times yet no evidence for AGN activity: Abell 1650 and Abell 2244. The cores of these clusters indeed appear systematically different from cores with more prominent radio emission. They do not have significant central temperature gradients, and their central entropy levels are markedly higher than in clusters with stronger radio emission, corresponding to central cooling times ~ 1 Gyr. Also, there is no evidence for fossil X-ray cavities produced by an earlier episode of AGN heating. We suggest that either (1) the central gas has not yet cooled to the point at which feedback is necessary to prevent it from condensing, possibly because it is conductively stabilized, or (2) the gas experienced a major heating event & \u3e~ Gyr in the past and has not required feedback since then. The fact that these clusters with no evident feedback have higher central entropy and therefore longer central cooling times than clusters with obvious AGN feedback strongly suggests that AGNs supply the feedback necessary to suppress condensation in clusters with short central cooling times (Refer to PDF file for exact formulas)
AGN Driven Weather and Multiphase Gas in the Core of the NGC 5044 Galaxy Group
A deep Chandra observation of the X-ray bright group, NGC 5044, shows that
the central region of this group has been strongly perturbed by repeated AGN
outbursts. These recent AGN outbursts have produced many small X-ray cavities,
cool filaments and cold fronts. We find a correlation between the coolest X-ray
emitting gas and the morphology of the Ha filaments. The Ha filaments are
oriented in the direction of the X-ray cavities, suggesting that the warm gas
responsible for the Halpha emission originated near the center of NGC 5044 and
was dredged up behind the buoyant, AGN-inflated X-ray cavities. A detailed
spectroscopic analysis shows that the central region of NGC 5044 contains
spatially varying amounts of multiphase gas. The regions with the most
inhomogeneous gas temperature distribution tend to correlate with the extended
235 MHz and 610 MHz radio emission detected by the GMRT. This may result from
gas entrainment within the radio emitting plasma or mixing of different
temperature gas in the regions surrounding the radio emitting plasma by AGN
induced turbulence. Accounting for the effects of multiphase gas, we find that
the abundance of heavy elements is fairly uniform within the central 100 kpc,
with abundances of 60-80% solar for all elements except oxygen, which has a
significantly sub-solar abundance. In the absence of continued AGN outbursts,
the gas in the center of NGC 5044 should attain a more homogeneous distribution
of gas temperature through the dissipation of turbulent kinetic energy and heat
conduction in approximately 10e8 yr. The presence of multiphase gas in NGC 5044
indicates that the time between recent AGN outbursts has been less than
approximately 10e8 yr
Luttinger Parameter g for Metallic Carbon Nanotubes and Related Systems
The random phase approximation (RPA) theory is used to derive the Luttinger
parameter g for metallic carbon nanotubes. The results are consistent with the
Tomonaga-Luttinger models. All metallic carbon nanotubes, regardless if they
are armchair tubes, zigzag tubes, or chiral tubes, should have the same
Luttinger parameter g. However, a (10,10) carbon peapod should have a smaller g
value than a (10,10) carbon nanotube. Changing the Fermi level by applying a
gate voltage has only a second order effect on the g value. RPA theory is a
valid approach to calculate plasmon energy in carbon nanotube systems,
regardless if the ground state is a Luttinger liquid or Fermi liquid. (This
paper was published in PRB 66, 193405 (2002). However, Eqs. (6), (9), and (19)
were misprinted there.)Comment: 2 figure
RIPK3-mediated cell death is involved in DUX4-mediated toxicity in facioscapulohumeral dystrophy
BACKGROUND: Facioscapulohumeral dystrophy (FSHD) is caused by mutations leading to the aberrant expression of the DUX4 transcription factor in muscles. DUX4 was proposed to induce cell death, but the involvement of different death pathways is still discussed. A possible pro‐apoptotic role of DUX4 was proposed, but as FSHD muscles are characterized by necrosis and inflammatory infiltrates, non‐apoptotic pathways may be also involved. METHODS: We explored DUX4‐mediated cell death by focusing on the role of one regulated necrosis pathway called necroptosis, which is regulated by RIPK3. We investigated the effect of necroptosis on cell death in vitro and in vivo experiments using RIPK3 inhibitors and a RIPK3‐deficient transgenic mouse model. RESULTS: We showed in vitro that DUX4 expression causes a caspase‐independent and RIPK3‐mediated cell death in both myoblasts and myotubes. In vivo, RIPK3‐deficient animals present improved body and muscle weights, a reduction of the aberrant activation of the DUX4 network genes, and an improvement of muscle histology. CONCLUSIONS: These results provide evidence for a role of RIPK3 in DUX4‐mediated cell death and open new avenues of research
CellWhere: graphical display of interaction networks organized on subcellular localizations
International audienceGiven a query list of genes or proteins, CellWhere produces an interactive graphical display that mimics the structure of a cell, showing the local interaction network organized into subcellular locations. This user-friendly tool helps in the formulation of mechanistic hypotheses by enabling the experimental biologist to explore simultaneously two elements of functional context: (i) protein subcellular localization and (ii) protein–protein interactions or gene functional associations. Subcellular localization terms are obtained from public sources (the Gene Ontology and UniProt—together containing several thousand such terms) then mapped onto a smaller number of CellWhere localizations. These localizations include all major cell compartments, but the user may modify the mapping as desired. Protein–protein interaction listings, and their associated evidence strength scores, are obtained from the Mentha interactome server, or power-users may upload a pre-made network produced using some other interactomics tool. The Cytoscape.js JavaScript library is used in producing the graphical display. Importantly, for a protein that has been observed at multiple subcellular locations, users may prioritize the visual display of locations that are of special relevance to their research domain. CellWhere is at http://cellwhere-myology.rhcloud.com
Skeletal muscle characteristics are preserved in hTERT/cdk4 human myogenic cell lines
Background: hTERT/cdk4 immortalized myogenic human cell lines represent an important tool for skeletal muscle research, being used as therapeutically pertinent models of various neuromuscular disorders and in numerous fundamental studies of muscle cell function. However, the cell cycle is linked to other cellular processes such as integrin regulation, the PI3K/Akt pathway, and microtubule stability, raising the question as to whether genetic modification related to the cell cycle results in secondary effects that could undermine the validity of these cell models.Results: Here we subjected five healthy and disease muscle cell isolates to transcriptomic analysis, comparing immortalized lines with their parent primary populations in both differentiated and undifferentiated states, and testing their myogenic character by comparison with non-myogenic (CD56-negative) cells. Principal component analysis of global gene expression showed tight clustering of immortalized myoblasts to their parent primary populations, with clean separation from the non-myogenic reference. Comparison was made to publicly available transcriptomic data from studies of muscle human pathology, cell, and animal models, including to derive a consensus set of genes previously shown to have altered regulation during myoblast differentiation. Hierarchical clustering of samples based on gene expression of this consensus set showed that immortalized lines retained the myogenic expression patterns of their parent primary populations. Of 2784 canonical pathways and gene ontology terms tested by gene set enrichment analysis, none were significantly enriched in immortalized compared to primary cell populations. We observed, at the whole transcriptome level, a strong signature of cell cycle shutdown associated with senescence in one primary myoblast population, whereas its immortalized clone was protected.Conclusions: Immortalization had no observed effect on the myogenic cascade or on any other cellular processes, and it was protective against the systems level effects of senescence that are observed at higher division counts of primary cells
HST viewing of spectacular star-forming trails behind ESO 137-001
We present the results from the HST WFC3 and ACS data on an archetypal galaxy
undergoing ram pressure stripping (RPS), ESO 137-001, in the nearby cluster
Abell 3627. ESO 137-001 is known to host a prominent stripped tail detected in
many bands from X-rays, Halpha to CO. The HST data reveal significant features
indicative of RPS such as asymmetric dust distribution and surface brightness
as well as many blue young star complexes in the tail. We study the correlation
between the blue young star complexes from HST, HII regions from Halpha (MUSE)
and dense molecular clouds from CO (ALMA). The correlation between the HST blue
star clusters and the HII regions is very good, while their correlation with
the dense CO clumps are typically not good, presumably due in part to
evolutionary effects. In comparison to the Starburst99+Cloudy model, many blue
regions are found to be young (< 10 Myr) and the total star formation (SF) rate
in the tail is 0.3 - 0.6 M_Sun/yr for sources measured with ages less than 100
Myr, about 40% of the SF rate in the galaxy. We trace SF over at least 100 Myr
and give a full picture of the recent SF history in the tail. We also
demonstrate the importance of including nebular emissions and a nebular to
stellar extinction correction factor when comparing the model to the broadband
data. Our work on ESO 137-001 demonstrates the importance of HST data for
constraining the SF history in stripped tails.Comment: 21 pages, 19 figures, 4 tables, re-submitted to MNRAS (initial
submission on Aug. 4, 2022