66 research outputs found
The Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER). III. The Mass Function of Young Star Clusters in M33
We measure the star cluster mass function for the Local Group galaxy M33. We
use the catalog of stellar clusters selected from the Panchromatic Hubble
Andromeda Treasury: Triangulum Extended Region (PHATTER) survey. We analyze 711
clusters in M33 with
3.0 as determined from color-magnitude diagram fits to individual stars. The
M33 cluster mass function is best described by a Schechter function with power
law slope , and truncation mass
log() . The data show strong evidence
for a high-mass truncation, thus strongly favoring a Schechter function fit
over a pure power law. M33's truncation mass is consistent with the previously
identified linear trend between , and star formation rate surface density,
\SigSFR. We also explore the effect that individual cluster mass uncertainties
have on derived mass function parameters, and find evidence to suggest that
large cluster mass uncertainties have the potential to bias the truncation mass
of fitted mass functions on the one sigma level.Comment: 18 pages, 15 figures, 1 table, Accepted to ApJ (February 2, 2022
Tidal Dwarf Galaxies at Intermediate Redshifts
We present the first attempt at measuring the production rate of tidal dwarf
galaxies (TDGs) and estimating their contribution to the overall dwarf
population. Using HST/ACS deep imaging data from GOODS and GEMS surveys in
conjunction with photometric redshifts from COMBO-17 survey, we performed a
morphological analysis for a sample of merging/interacting galaxies in the
Extended Chandra Deep Field South and identified tidal dwarf candidates in the
rest-frame optical bands. We estimated a production rate about 1.4 {\times}
10^{-5} per Gyr per comoving volume for long-lived TDGs with stellar mass 3
{\times} 10^{8-9} solar mass at 0.5<z<1.1. Together with galaxy merger rates
and TDG survival rate from the literature, our results suggest that only a
marginal fraction (less than 10%) of dwarf galaxies in the local universe could
be tidally-originated. TDGs in our sample are on average bluer than their host
galaxies in the optical. Stellar population modelling of optical to
near-infrared spectral energy distributions (SEDs) for two TDGs favors a burst
component with age 400/200 Myr and stellar mass 40%/26% of the total,
indicating that a young stellar population newly formed in TDGs. This is
consistent with the episodic star formation histories found for nearby TDGs.Comment: 9 pages, 5 figures, Accepted for publication in Astrophysics & Space
Scienc
Toward an internally consistent astronomical distance scale
Accurate astronomical distance determination is crucial for all fields in
astrophysics, from Galactic to cosmological scales. Despite, or perhaps because
of, significant efforts to determine accurate distances, using a wide range of
methods, tracers, and techniques, an internally consistent astronomical
distance framework has not yet been established. We review current efforts to
homogenize the Local Group's distance framework, with particular emphasis on
the potential of RR Lyrae stars as distance indicators, and attempt to extend
this in an internally consistent manner to cosmological distances. Calibration
based on Type Ia supernovae and distance determinations based on gravitational
lensing represent particularly promising approaches. We provide a positive
outlook to improvements to the status quo expected from future surveys,
missions, and facilities. Astronomical distance determination has clearly
reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press
(chapter 8 of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age
Studies of jet production rates in e + e − annihilation at E cm =29 GeV
Production rates of multijet hadronic final states are studied in e + e − annihilation at 29 GeV center of mass energy. QCD shower model calculations with exact first order matrix element weighting at the first gluon vertex are capable of reproducing the observed multijet event rates over a large range of jet pair masses. The method used to reconstruct jets is well suited for directly comparing experimental jet rates with parton rates calculated in perturbative QCD. Evidence for the energy dependene of α s is obtained by comparing the observed production rates of 3-jet events with results of similar studies performed at higher center of mass energies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47886/1/10052_2005_Article_BF01506527.pd
A MODEST review
We present an account of the state of the art in the fields explored by the
research community invested in 'Modeling and Observing DEnse STellar systems'.
For this purpose, we take as a basis the activities of the MODEST-17
conference, which was held at Charles University, Prague, in September 2017.
Reviewed topics include recent advances in fundamental stellar dynamics,
numerical methods for the solution of the gravitational N-body problem,
formation and evolution of young and old star clusters and galactic nuclei,
their elusive stellar populations, planetary systems, and exotic compact
objects, with timely attention to black holes of different classes of mass and
their role as sources of gravitational waves.
Such a breadth of topics reflects the growing role played by collisional
stellar dynamics in numerous areas of modern astrophysics. Indeed, in the next
decade, many revolutionary instruments will enable the derivation of positions
and velocities of individual stars in the Milky Way and its satellites and will
detect signals from a range of astrophysical sources in different portions of
the electromagnetic and gravitational spectrum, with an unprecedented
sensitivity. On the one hand, this wealth of data will allow us to address a
number of long-standing open questions in star cluster studies; on the other
hand, many unexpected properties of these systems will come to light,
stimulating further progress of our understanding of their formation and
evolution.Comment: 42 pages; accepted for publication in 'Computational Astrophysics and
Cosmology'. We are much grateful to the organisers of the MODEST-17
conference (Charles University, Prague, September 2017). We acknowledge the
input provided by all MODEST-17 participants, and, more generally, by the
members of the MODEST communit
Recommended from our members
On the Reionization-era Globular Cluster in the Low-mass Galaxy Eridanus II
Using color-magnitude diagrams from deep archival Hubble Space Telescope imaging, we self-consistently measure the star formation history of Eridanus II (Eri II), the lowest-mass galaxy (M ⋆(z = 0) ∼ 105 M ⊙) known to host a globular cluster (GC), and the age, mass, and metallicity of its GC. The GC (∼13.2 ± 0.4 Gyr, 〈[Fe/H]〉 = −2.75 ± 0.2 dex) and field (mean age ∼13.5 ± 0.3 Gyr, 〈[Fe/H]〉 = −2.6 ± 0.15 dex) have similar ages and metallicities. Both are reionization-era relics that formed before the peak of cosmic star and GC formation (z ∼ 2-4). The ancient star formation properties of Eri II are not extreme and appear similar to z = 0 dwarf galaxies. We find that the GC was ≲4 times more massive at birth than today and was ∼10% of the galaxy's stellar mass at birth. At formation, we estimate that the progenitor of Eri II and its GC had M UV ∼ −7 to −12, making it one of the most common type of galaxy in the early universe, though it is fainter than direct detection limits, absent gravitational lensing. Archaeological studies of GCs in nearby low-mass galaxies may be the only way to constrain GC formation in such low-mass systems. We discuss the strengths and limitations in comparing archaeological and high-redshift studies of cluster formation, including challenges stemming from the Hubble Tension, which introduces uncertainties into the mapping between age and redshift. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
The progenitors of the Milky Way stellar halo: big bricks favoured over little bricks
We present a census of blue horizontal branch (BHB) and blue straggler (BS) stars belonging to dwarf galaxies and globular clusters, and compare these counts to that of the Milky Way stellar halo. We find, in agreement with earlier studies, that the ratio of BS-to-BHB stars in these satellite populations is dependent on stellar mass. Dwarf galaxies show an increasing BS-to-BHB ratio with luminosity. In contrast, globular clusters display the reverse trend, with NBS/NBHB (≲ 1) decreasing with luminosity. The faintest (L < 105 Lȯ) dwarfs have similar numbers of BS and BHB stars (NBS/NBHB ∼ 1), whereas more-massive dwarfs tend to be dominated by BS stars (NBS/NBHB ∼ 2–40). We find that the BS-to-BHB ratio in the stellar halo is relatively high (NBS/NBHB ∼ 5–6), and thus inconsistent with the low ratios found in both ultra-faint dwarfs and globular clusters. Our results favour more-massive dwarfs as the dominant ‘building blocks’ of the stellar halo, in good agreement with current predictions from Λ cold dark matter models
The Snapshot Hubble U-band Cluster Survey (SHUCS). I. Survey Description and First Application to the Mixed Star Cluster Population of NGC 4041
Contains fulltext :
111270.pdf (preprint version ) (Open Access
Panchromatic Hubble Andromeda Treasury. XVI. Star Cluster Formation Efficiency and the Clustered Fraction of Young Stars
Contains fulltext :
159663.pdf (preprint version ) (Open Access)33 p
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