109 research outputs found
H I in group interactions: HCG 44
Extending deep observations of the neutral atomic hydrogen (HI) to the
environment around galaxy groups can reveal a complex history of group
interactions which is invisible to studies that focus on the stellar component.
Hickson Compact Group 44 (HCG 44) is a nearby example and we have combined HI
data from the Karoo Array Telescope, Westerbork Synthesis Radio Telescope, and
Arecibo Legacy Fast ALFA survey, in order to achieve high column density
sensitivity (N_HI < 2x10^18 cm^-2) to the neutral gas over a large
field-of-view beyond the compact group itself. We find the giant HI tail north
of HCG 44 contains 1.1x10^9 M_Sun of gas and extends 450 kpc from the compact
group: twice as much mass and 33% further than previously detected. However,
the additional gas is still unable to account for the known HI deficiency of
HCG 44. The tail likely formed through a strong tidal interaction and HI clouds
in the tail have survived for 1 Gyr or more after being stripped. This has
important implications for understanding the survival of neutral clouds in the
intragroup and circumgroup medium, and we discuss their survival in the context
of simulations of cold gas in hot halos. HCG 44 is one of a growing number of
galaxy groups found to have more extended HI in the intragroup and circumgroup
medium than previously measured. Our results provide constraints for
simulations on the properties of galaxy group halos, and reveal a glimpse of
what will be seen by future powerful HI telescopes and surveys.Comment: 12 pages, 6 figures. Accepted for publication in MNRA
Radio Continuum and Star Formation in CO-rich Early Type Galaxies
In this paper we present new high resolution VLA 1.4 GHz radio continuum
observations of five FIR bright CO-rich early-type galaxies and two dwarf
early-type galaxies. The position on the radio-FIR correlation combined with
striking agreements in morphology between high resolution CO and radio maps
show that the radio continuum is associated with star formation in at least
four of the eight galaxies. The average star formation rate for the sample
galaxies detected in radio is approximately 2 solar masses per year. There is
no evidence of a luminous AGN in any of our sample galaxies. We estimate Toomre
Q values and find that the gas disks may well be gravitationally unstable,
consistent with the above evidence for star formation activity. The radio
continuum emission thus corroborates other recent suggestions that star
formation in early type galaxies may not be uncommon.Comment: 21 pages, 7 figures, to be published in the Astronomical Journa
Modifiable Cardiovascular Disease Risk Factors among Indigenous Populations
Objective:. To identify modifiable cardio-metabolic and lifestyle risk factors among indigenous populations from Australia (Aboriginal Australians/Torres Strait Islanders), New Zealand (Māori), and the United States (American Indians and Alaska Natives) that contribute to cardiovascular disease (CVD). Methods:. National health surveys were identified where available. Electronic databases identified sources for filling missing data. The most relevant data were identified, organized, and synthesized. Results:. Compared to their non-indigenous counterparts, indigenous populations exhibit lower life expectancies and a greater prevalence of CVD. All indigenous populations have higher rates of obesity and diabetes, hypertension is greater for Māori and Aboriginal Australians, and high cholesterol is greater only among American Indians/Alaska Natives. In turn, all indigenous groups exhibit higher rates of smoking and dangerous alcohol behaviour as well as consuming less fruits and vegetables. Aboriginal Australians and American Indians/Alaska Natives also exhibit greater rates of sedentary behaviour. Conclusion:. Indigenous groups from Australia, New Zealand, and the United States have a lower life expectancy then their respective non-indigenous counterparts. A higher prevalence of CVD is a major driving force behind this discrepancy. A cluster of modifiable cardio-metabolic risk factors precede CVD, which, in turn, is linked to modifiable lifestyle risk factors
Regulation der Genexpression von MYCN in humanen Neuoblastomzellen durch Transkriptionsfaktoren der E2F-Familie
Seit fast 30 Jahren ist bekannt, dass die Amplifikation und Expression des Onkogens MYCN in Neuroblastomen mit einer sehr ungünstigen Prognose für die Patienten einhergeht. Dennoch liegen die Mechanismen der Genregulation von MYCN weiterhin größtenteils im Dunkeln.
Die Präsenz potentieller Bindungsstellen für E2F-Proteine im Promotor des MYCN-Gens sowie Zellkulturexperimente lieferten Hinweise auf eine Rolle der Transkriptionsfaktoren der E2F-Familie in der Regulation der N-myc-Expression.
Ziel dieser Arbeit war die Beantwortung der Frage, ob E2F-Proteine notwendig sind, um eine primär hohe Expression von N-myc in Neuroblastomzellen mit Amplifikation des Onkogens aufrechtzuerhalten, und ob sie hinreichend sind, um die Transkription von MYCN in Zellen ohne endogene Expression von N-myc einzuleiten.
Durch Überexpression des Tumorsuppressorproteins p16, welches zu einer Inaktivierung endogener E2F-Proteine führt, konnte die MYCN-mRNA-Menge in Neuroblastomzellen deutlich gesenkt werden. Vergleichbare Resultate wurden durch Expression von dominant negativem E2F-1 erzielt. Da in einigen Studien gezeigt werden konnte, dass Myc-Proteine ihrerseits E2F-Gene aktivieren können, nehmen wir an, in aggressiven Neuroblastomen könnte eine positive Rückkopplungsschleife zwischen E2F-Transkriptionsfaktoren auf der einen und N-myc auf der anderen Seite existieren, die die gesteigerte Aktivität des MYCN-Onkogens aufrechterhält.
Stabil transfizierte E2F-ER-Fusionsproteine waren jedoch nicht in der Lage, das endogene MYCN-Gen in Neuroblastomzellen ohne Expression von N-myc anzuschalten. E2F-Proteine werden folglich für das volle Ausmaß der starken Expression von N-myc in Neuroblastomen benötigt, sind aber nicht ausreichend, um das Onkogen MYCN in Zellen ohne endogenes N-myc zu aktivieren.
In der Zukunft könnte durch Verhinderung der Bindung von E2F-Proteinen an den MYCN-Promotor oder durch gentherapeutische Ansätze, die z.B. mittels viraler Infektion den Signalweg zwischen p16 und E2F rekonstruieren, die Expression von N-myc in Neuroblastomen gesenkt werden, so dass die Aggressivität der Tumore reduziert und die individuelle Prognose der Patienten verbessert werden könnte
CHILES: HI morphology and galaxy environment at z=0.12 and z=0.17
We present a study of 16 HI-detected galaxies found in 178 hours of
observations from Epoch 1 of the COSMOS HI Large Extragalactic Survey (CHILES).
We focus on two redshift ranges between 0.108 <= z <= 0.127 and 0.162 <= z <=
0.183 which are among the worst affected by radio frequency interference (RFI).
While this represents only 10% of the total frequency coverage and 18% of the
total expected time on source compared to what will be the full CHILES survey,
we demonstrate that our data reduction pipeline recovers high quality data even
in regions severely impacted by RFI. We report on our in-depth testing of an
automated spectral line source finder to produce HI total intensity maps which
we present side-by-side with significance maps to evaluate the reliability of
the morphology recovered by the source finder. We recommend that this become a
common place manner of presenting data from upcoming HI surveys of resolved
objects. We use the COSMOS 20k group catalogue, and we extract filamentary
structure using the topological DisPerSE algorithm to evaluate the \hi\
morphology in the context of both local and large-scale environments and we
discuss the shortcomings of both methods. Many of the detections show disturbed
HI morphologies suggesting they have undergone a recent interaction which is
not evident from deep optical imaging alone. Overall, the sample showcases the
broad range of ways in which galaxies interact with their environment. This is
a first look at the population of galaxies and their local and large-scale
environments observed in HI by CHILES at redshifts beyond the z=0.1 Universe.Comment: 23 pages, 12 figures, 1 interactive 3D figure, accepted to MNRA
Chromatic periodic activity down to 120 MHz in a Fast Radio Burst
Fast radio bursts (FRBs) are extragalactic astrophysical transients whose
brightness requires emitters that are highly energetic, yet compact enough to
produce the short, millisecond-duration bursts. FRBs have thus far been
detected between 300 MHz and 8 GHz, but lower-frequency emission has remained
elusive. A subset of FRBs is known to repeat, and one of those sources, FRB
20180916B, does so with a 16.3 day activity period. Using simultaneous Apertif
and LOFAR data, we show that FRB 20180916B emits down to 120 MHz, and that its
activity window is both narrower and earlier at higher frequencies. Binary wind
interaction models predict a narrower periodic activity window at lower
frequencies, which is the opposite of our observations. Our detections
establish that low-frequency FRB emission can escape the local medium. For
bursts of the same fluence, FRB 20180916B is more active below 200 MHz than at
1.4 GHz. Combining our results with previous upper-limits on the all-sky FRB
rate at 150 MHz, we find that there are 3-450 FRBs/sky/day above 50 Jy ms at
90% confidence. We are able to rule out the scenario in which companion winds
cause FRB periodicity. We also demonstrate that some FRBs live in clean
environments that do not absorb or scatter low-frequency radiation.Comment: 50 pages, 14 figures, 3 tables, submitte
MIGHTEE-\HI: Possible interactions with the galaxy NGC~895
The transformation and evolution of a galaxy is strongly influenced by
interactions with its environment. Neutral hydrogen (\HI) is an excellent way
to trace these interactions. Here, we present \HI\ observations of the spiral
galaxy NGC~895, which was previously thought to be isolated. High-sensitivity
\HI\ observations from the MeerKAT large survey project MIGHTEE reveal possible
interaction features, such as extended spiral arms, and the two newly
discovered \HI\ companions, that drive us to change the narrative that it is an
isolated galaxy. We combine these observations with deep optical images from
the Hyper Suprime Camera to show an absence of tidal debris between NGC 895 and
its companions. We do find an excess of light in the outer parts of the
companion galaxy MGTHJ022138.1-052631 which could be an indication of
external perturbation and thus possible sign of interactions. Our analysis
shows that NGC~895 is an actively star-forming galaxy with a SFR of
, a value typical for high stellar mass
galaxies on the star forming main sequence. It is reasonable to state that
different mechanisms may have contributed to the observed features in NGC~895
and this emphasizes the need to revisit the target with more detailed
observations. Our work shows the high potential and synergy of using
state-of-the-art data in both \HI\ and optical to reveal a more complete
picture of galaxy environments.Comment: 14 pages, 10 figures. Accepted for publication in MNRA
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