3,029 research outputs found
Neutral hydrogen gas, past and future star-formation in galaxies in and around the 'Sausage' merging galaxy cluster
CIZA J2242.8+5301 (, nicknamed 'Sausage') is an extremely massive
( ), merging cluster with shock waves
towards its outskirts, which was found to host numerous emission-line galaxies.
We performed extremely deep Westerbork Synthesis Radio Telescope HI
observations of the 'Sausage' cluster to investigate the effect of the merger
and the shocks on the gas reservoirs fuelling present and future star formation
(SF) in cluster members. By using spectral stacking, we find that the
emission-line galaxies in the 'Sausage' cluster have, on average, as much HI
gas as field galaxies (when accounting for the fact cluster galaxies are more
massive than the field galaxies), contrary to previous studies. Since the
cluster galaxies are more massive than the field spirals, they may have been
able to retain their gas during the cluster merger. The large HI reservoirs are
expected to be consumed within Gyr by the vigorous SF and AGN
activity and/or driven out by the out-flows we observe. We find that the
star-formation rate in a large fraction of H emission-line cluster
galaxies correlates well with the radio broad band emission, tracing supernova
remnant emission. This suggests that the cluster galaxies, all located in
post-shock regions, may have been undergoing sustained SFR for at least 100
Myr. This fully supports the interpretation proposed by Stroe et al. (2015) and
Sobral et al. (2015) that gas-rich cluster galaxies have been triggered to form
stars by the passage of the shock.Comment: Accepted to MNRAS, 14 pages, 9 figures, 7 table
High Resolution OI (630 nm) Image Measurements of Fregion Depletion Drifts During the Guara Campaign
A high performance, allâsky, imaging system has provided data on the evolution and drift motions of Fâregion depletions above the magnetic dip equator at AlcĂąntara, Brazil, (2.3°S, 44.5°W). Monochromatic images of depletions in the OI(630 nm) nightglow were recorded on eight nights during 1â16 October, 1994, as part of the GuarĂĄ campaign. The drift motions of the depletions were typically 80â100 m/s eastward prior to local midnight and reduced to a minimum of âŒ30â50 m/s in the morning hours, in accord with previous observations. However, on October 2â3 and 12â13 the depletions were observed to reverse direction for âŒ60â90 min, achieving westward speeds of âŒ30 m/s before the motion reverted to eastward around 0100 LT and accelerated to 35â45 m/s near dawn. Magnetic activity and other evidence suggests that these reversals in the motion of the airglow depletions probably result from reversals in the Fâregion dynamo rather than from shifts in the altitude of the shear in the nighttime Fâregion plasma drift
Guia pråtico para a adubação da laranjeira com base em anålises de solo e folha.
bitstream/item/142259/1/Doc-205.pd
InfluĂȘncia da calagem no estado nutricional da laranjeira 'PĂȘra' (Citrus sinensis, L. Osbeck.) cultivada em argissolo dos tabuleiros costeiros.
bitstream/item/32642/1/bp-63.pd
The Brightest Ly Emitter: Pop III or Black Hole?
CR7 is the brightest emitter (LAE) known to date,
and spectroscopic follow-up by Sobral et al. (2015) suggests that CR7 might
host Population (Pop) III stars. We examine this interpretation using
cosmological hydrodynamical simulations. Several simulated galaxies show the
same "Pop III wave" pattern observed in CR7. However, to reproduce the extreme
CR7 /HeII1640 line luminosities () a
top-heavy IMF and a massive () PopIII burst with age
Myr are required. Assuming that the observed properties of and HeII emission are typical for Pop III, we predict that in the
COSMOS/UDS/SA22 fields, 14 out of the 30 LAEs at with should also host Pop III stars producing an
observable . As an alternate
explanation, we explore the possibility that CR7 is instead powered by
accretion onto a Direct Collapse Black Hole (DCBH). Our model predicts
, , and X-ray luminosities that are in agreement
with the observations. In any case, the observed properties of CR7 indicate
that this galaxy is most likely powered by sources formed from pristine gas. We
propose that further X-ray observations can distinguish between the two above
scenarios.Comment: 6 pages, 4 figure
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