10,131 research outputs found
A large narrow band H survey at : the bright end of the luminosity function, cosmic variance and clustering across cosmic time
We carried out the largest ( Mpc, 26 deg) H
narrow band survey to date at in the SA22, W2 and XMMLSS
extragalactic fields. Our survey covers a large enough volume to overcome
cosmic variance and to sample bright and rare H emitters up to an
observed luminosity of erg s, equivalent to yr. Using our sample of sources brighter than
erg s ( yr), we derive H
luminosity functions, which are well described by a Schechter function with
Mpc and
erg s (with a fixed faint end slope ). We find that
surveys probing smaller volumes ( Mpc) are heavily
affected by cosmic variance, which can lead to errors of over per cent in
the characteristic density and luminosity of the H luminosity function.
We derive a star formation rate density of yr, in agreement with the redshift-dependent
H parametrisation from Sobral et al. (2013). The two-point correlation
function is described by a single power law , corresponding to a clustering length of Mpc/h. We find that the most luminous H emitters at
are more strongly clustered than the relatively fainter ones. The
H emitters at in our sample reside in
dark matter haloes. This implies that the most
star forming galaxies always reside in relatively massive haloes or group-like
environments and that the typical host halo mass of star-forming galaxies is
independent of redshift if scaled by , as
proposed by Sobral et al. (2010).Comment: Accepted for publication in MNRAS; 18 pages, 19 figures, 6 table
From fields to a super-cluster: the role of the environment at z=0.84 with HiZELS
At z=0, clusters are primarily populated by red, elliptical and massive
galaxies, while blue, spiral and lower-mass galaxies are common in low-density
environments. Understanding how and when these differences were established is
of absolute importance for our understanding of galaxy formation and evolution,
but results at high-z remain contradictory. By taking advantage of the widest
and deepest H-alpha narrow-band survey at z=0.84 over the COSMOS and UKIDSS UDS
fields, probing a wide range of densities (from poor fields to rich groups and
clusters, including a confirmed super-cluster with a striking filamentary
structure), we show that the fraction of star-forming galaxies falls
continuously from ~40% in fields to approaching 0% in rich groups/clusters. We
also find that the median SFR increases with environmental density, at least up
to group densities - but only for low and medium mass galaxies, and thus such
enhancement is mass-dependent at z~1. The environment also plays a role in
setting the faint-end slope (alpha) of the H-alpha luminosity function. Our
findings provide a sharper view on galaxy formation and evolution and reconcile
previously contradictory results at z~1: stellar mass is the primary predictor
of star formation activity, but the environment also plays a major role.Comment: 5 pages, 4 figures, to appear in the proceedings of JENAM 2010 S2:
`Environment and the Formation of Galaxies: 30 years later', ASSP, Springe
Schreier split extensions of preordered monoids
Properties of preordered monoids are investigated and important subclasses of
such structures are studied. The corresponding full subcategories of the
category of preordered monoids are functorially related between them as well as
with the categories of preordered sets and monoids. Schreier split extensions
are described in the full subcategory of preordered monoids whose preorder is
determined by the corresponding positive cone
On some categorical-algebraic conditions in S-protomodular categories
In the context of protomodular categories, several additional conditions have
been considered in order to obtain a closer group-like behavior. Among them are
locally algebraic cartesian closedness and algebraic coherence. The recent
notion of S-protomodular category, whose main examples are the category of
monoids and, more generally, categories of monoids with operations and
Jo\'{o}nsson-Tarski varieties, raises a similar question: how to get a
description of S-protomodular categories with a strong monoid-like behavior. In
this paper we consider relative versions of the conditions mentioned above, in
order to exhibit the parallelism with the "absolute" protomodular context and
to obtain a hierarchy among S-protomodular categories
Some notes on Esakia spaces
Under Stone/Priestley duality for distributive lattices, Esakia spaces
correspond to Heyting algebras which leads to the well-known dual equivalence
between the category of Esakia spaces and morphisms on one side and the
category of Heyting algebras and Heyting morphisms on the other. Based on the
technique of idempotent split completion, we give a simple proof of a more
general result involving certain relations rather then functions as morphisms.
We also extend the notion of Esakia space to all stably locally compact spaces
and show that these spaces define the idempotent split completion of compact
Hausdorff spaces. Finally, we exhibit connections with split algebras for
related monads
Comportamento de linhagens e cultivares de caupi (Vigna unguiculata (L. Walp.) de porte ereto, no estado de Rondonia.
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