Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stellar age spreads in clusters as imprints of cluster-parent clump
  densities   It has recently been suggested that high-density clusters have stellar age
distributions narrower than that of the Orion Nebula Cluster, indicating a
possible trend of narrower age distributions for denser clusters. We show this
effect to likely arise from star formation being faster in gas with a higher
density. We model the star formation history of molecular clumps in equilibrium
by associating a star formation efficiency (SFE) per free-fall time, \eff, to
their volume density profile. Our model predicts a steady decline of the star
formation rate (SFR), which we quantify with its half-life time, namely, the
time needed for the SFR to drop to half its initial value.
  Given the uncertainties affecting the SFE per free-fall time, we consider two
distinct values: 0.1 and 0.01. For isothermal spheres, \eff=0.1 leads to a
half-life time of order the clump free-fall time, \tff. Therefore, the age
distributions of stars formed in high-density clumps have smaller full-widths
at half-maximum than those of stars formed in low-density clumps. When
\eff=0.01, the half-life time is 10 times longer. We explore what happens if
the star formation duration is shorter than 10\tff, that is, if the half-life
time of the SFR cannot be defined. There, we build on the invariance of the
shape of the young cluster mass function to show that an anti-correlation
between clump density and star formation duration is expected. Therefore,
regardless of whether the star formation duration is longer than the SFR
half-life time, denser molecular clumps yield narrower star age distributions
in clusters.
  Published densities and stellar age spreads of young clusters actually
suggest that the time-scale for star formation is of order 1-4\tff. We conclude
that there is no need to invoke the existence of multiple cluster formation
mechanisms to explain the observed range of stellar age spreads in clusters.

22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin