48 research outputs found
Dust-Obscured Star-Formation in Intermediate Redshift Galaxy Clusters
We present Spitzer MIPS 24-micron observations of 16 0.4<z<0.8 galaxy
clusters drawn from the ESO Distant Cluster Survey (EDisCS). This is the first
large 24-micron survey of clusters at intermediate redshift. The depth of our
imaging corresponds to a total IR luminosity of 8x10^10 Lsun, just below the
luminosity of luminous infrared galaxies (LIRGs), and 6^{+1}_{-1}% of M_V < -19
cluster members show 24-micron emission at or above this level. We compare with
a large sample of coeval field galaxies and find that while the fraction of
cluster LIRGs lies significantly below that of the field, the IR luminosities
of the field and cluster galaxies are consistent. However, the stellar masses
of the EDisCS LIRGs are systematically higher than those of the field LIRGs. A
comparison with optical data reveals that ~80% of cluster LIRGs are blue and
the remaining 20% lie on the red sequence. Of LIRGs with optical spectra,
88^{+4}_{-5}% show [O II] emission with EW([O II])>5A, and ~75% exhibit optical
signatures of dusty starbursts. On average, the fraction of cluster LIRGs
increases with projected cluster-centric radius but remains systematically
lower than the field fraction over the area probed (< 1.5xR200). The amount of
obscured star formation declines significantly over the 2.4 Gyr interval
spanned by the EDisCS sample, and the rate of decline is the same for the
cluster and field populations. Our results are consistent with an exponentially
declining LIRG fraction, with the decline in the field delayed by ~1 Gyr
relative to the clusters.Comment: 15 pages, 9 figure
HOXA9 Reprograms the Enhancer Landscape to Promote Leukemogenesis
Aberrant expression of HOXA9 is a prominent feature of acute leukemia driven by diverse oncogenes. Here we show that HOXA9 overexpression in myeloid and B progenitor cells leads to significant enhancer reorganizations with prominent emergence of leukemia-specific de novo enhancers. Alterations in the enhancer landscape lead to activation of an ectopic embryonic gene program. We show that HOXA9 functions as a pioneer factor at de novo enhancers and recruits CEBPα and the MLL3/MLL4 complex. Genetic deletion of MLL3/MLL4 blocks histone H3K4 methylation at de novo enhancers and inhibits HOXA9/MEIS1-mediated leukemogenesis in vivo. These results suggest that therapeutic targeting of HOXA9-dependent enhancer reorganization can be an effective therapeutic strategy in acute leukemia with HOXA9 overexpressio
The Rest-Frame Optical Luminosity Function of Cluster Galaxies at z<0.8 and the Assembly of the Cluster Red Sequence
We present the rest-frame optical luminosity function (LF) of red sequence
galaxies in 16 clusters at 0.4<z<0.8 drawn from the ESO Distant Cluster Survey
(EDisCS). We compare our clusters to an analogous sample from the Sloan Digital
Sky Survey (SDSS) and match the EDisCS clusters to their most likely
descendants. We measure all LFs down to M M* + (2.5 - 3.5). At z<0.8, the
bright end of the LF is consistent with passive evolution but there is a
significant build-up of the faint end of the red sequence towards lower
redshift. There is a weak dependence of the LF on cluster velocity dispersion
for EDisCS but no such dependence for the SDSS clusters. We find tentative
evidence that red sequence galaxies brighter than a threshold magnitude are
already in place, and that this threshold evolves to fainter magnitudes toward
lower redshifts. We compare the EDisCS LFs with the LF of co-eval red sequence
galaxies in the field and find that the bright end of the LFs agree. However,
relative to the number of bright red galaxies, the field has more faint red
galaxies than clusters at 0.6<z<0.8 but fewer at 0.4<z<0.6, implying
differential evolution. We compare the total light in the EDisCS cluster red
sequences to the total red sequence light in our SDSS cluster sample. Clusters
at 0.4<z<0.8 must increase their luminosity on the red sequence (and therefore
stellar mass in red galaxies) by a factor of 1-3 by z=0. The necessary
processes that add mass to the red sequence in clusters predict local clusters
that are over-luminous as compared to those observed in the SDSS. The predicted
cluster luminosities can be reconciled with observed local cluster luminosities
by combining multiple previously known effects.Comment: Accepted for publication in the Astrophysical Journal. 36 pages, 16
figures, 10 table
Investigation of inclusions trapped inside Libyan desert glass by Raman microscopy
Several specimens of Libyan Desert Glass (LDG), an enigmatic natural glass from Egypt, were subjected to investigation by micro-Raman spectroscopy. The spectra of inclusions inside the LDG samples were successfully measured through the layers of glass and the mineral species were identified on this basis. The presence of cristobalite as typical for high-temperature melt products was confirmed, together with co-existing quartz. TiO2 was determined in two polymorphic species, rutile and anatase. Micro-Raman spectroscopy proved also the presence of minerals unusual for high-temperature glasses such as anhydrite and aragonite