Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bulgeless Galaxies and their Angular Momentum Problem   The specific angular momentum of Cold Dark Matter (CDM) halos in a
$\Lambda$CDM universe is investigated. Their dimensionless specific angular
momentum $\lambda'=\frac{j}{\sqrt{2}V_{vir} R{vir}}$ with $V_{vir}$ and
$R_{vir}$ the virial velocity and virial radius, respectively depends strongly
on their merging histories. We investigate a set of $\Lambda$CDM simulations
and explore the specific angular momentum content of halos formed through
various merging histories. Halos with a quiet merging history, dominated by
minor mergers and accretion until the present epoch, acquire by tidal torques
on average only 2% to 3% of the angular momentum required for their rotational
support ($\lambda'=0.02$). This is in conflict with observational data for a
sample of late-type bulgeless galaxies which indicates that those galaxies
reside in dark halos with exceptionally high values of $\lambda' \approx
0.06-0.07$. Minor mergers and accretion preserve or slowly increase the
specific angular momentum of dark halos with time. This mechanism is however
not efficient enough in order to explain the observed spin values for late-type
dwarf galaxies. Energetic feedback processes have been invoked to solve the
problem that gas loses a large fraction of its specific angular momentum during
infall. Under the assumption that dark halos hosting bulgeless galaxies acquire
their mass via quiescent accretion, our results indicate yet another serious
problem: the specific angular momentum gained during the formation of these
objects is not large enough to explain their observed rotational
properties,even if no angular momentum would be lost during gas infall.

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The categories of this paper are: cs
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The categories of this paper are: math-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: q-bio
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The categories of this paper are: supr-con
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The categories of this paper are: nucl-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-lat
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The categories of this paper are: physics
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The categories of this paper are: chem-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin
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The categories of this paper are: solv-int
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The categories of this paper are: stat
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The categories of this paper are: bayes-an