The Arches cluster out to its tidal radius: dynamical mass segregation and the effect of the extinction law on the stellar mass function

AbstractRecent observations have revealed the existence of stellar mass black hole (BH) candidates in some globular clusters (GC) in the Milky Way and in other galaxies. Given that the detection of BHs is challenging, these detections likely indicate the existence of large populations of BHs in these clusters. This is in direct contrast to the past understanding that at most a handful of BHs may remain in old GCs due to quick mass segregation and rapid mutual dynamical ejection. Modern realistic star-by-star numerical simulations suggest that the retention fraction of BHs is typically much higher than what was previously thought. The BH dynamics near the cluster center leads to dynamical formation of new binaries and dynamical ejections, and acts as a persistent and significant energy source for these clusters. We have started exploring effects of BHs on the global evolution and survival of star clusters. We find that the evolution as well as survival of massive star clusters can critically depend on the details of the initial assumptions related to BH formation physics, such as natal kick distribution, and the initial stellar mass function (IMF). In this article we will present our latest results.

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Dynamical modelling of brightest cluster galaxies: Constraints on the IMF

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319008093 ◽

2019 ◽

Vol 14 (S353) ◽

pp. 257-258

Author(s):

S. I. Loubser

Keyword(s):

Stellar Population ◽

Mass Function ◽

Stellar Mass ◽

Initial Mass Function ◽

Small Subset ◽

Dynamical Mass ◽

Cluster Galaxies ◽

Spatially Resolved ◽

Brightest Cluster Galaxies ◽

Massive Clusters

AbstractWe study the stellar and dynamical masses, as well as the stellar populations, of brightest cluster galaxies (BCGs) located in 32 massive clusters, and for a sub-sample of these use the results to place constraints on the Initial Mass Function (IMF). We measure the spatially-resolved stellar population properties of the BCGs, such as recent star formation episodes, and use it to predict their stellar mass-to-light ratios (ϒ*POP). We find that ∼60 per cent of the BCGs have constant ϒ*POP over the radial range (<15 kpc). We also use the stellar and dynamical mass profiles to derive the stellar mass-to-light ratio from dynamics (ϒ*DYN, see Loubser, these proceedings). We directly compare ϒ*POP with ϒ*DYN, and find that for most BCGs, a Salpeter IMF is needed to explain their properties, but we also find a small subset of BCGs for which a Kroupa-like IMF is needed to explain their properties.

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How robustly can we constrain the low-mass end of the z ∼ 6−7 stellar mass function? The limits of lensing models and stellar population assumptions in the Hubble Frontier Fields

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3760 ◽

2020 ◽

Vol 501 (2) ◽

pp. 1568-1590

Author(s):

Lukas J Furtak ◽

Hakim Atek ◽

Matthew D Lehnert ◽

Jacopo Chevallard ◽

Stéphane Charlot

Keyword(s):

Star Formation ◽

Mass Function ◽

Stellar Mass ◽

Star Formation History ◽

Space Telescope ◽

Formation History ◽

Low Mass ◽

Stellar Masses ◽

Dust Attenuation ◽

The Impact

ABSTRACT We present new measurements of the very low mass end of the galaxy stellar mass function (GSMF) at z ∼ 6−7 computed from a rest-frame ultraviolet selected sample of dropout galaxies. These galaxies lie behind the six Hubble Frontier Field clusters and are all gravitationally magnified. Using deep Spitzer/IRAC and Hubble Space Telescope imaging, we derive stellar masses by fitting galaxy spectral energy distributions and explore the impact of different model assumptions and parameter degeneracies on the resulting GSMF. Our sample probes stellar masses down to $M_{\star }\gt 10^{6}\, \text{M}_{\odot}$ and we find the z ∼ 6−7 GSMF to be best parametrized by a modified Schechter function that allows for a turnover at very low masses. Using a Monte Carlo Markov chain analysis of the GSMF, including accurate treatment of lensing uncertainties, we obtain a relatively steep low-mass end slope $\alpha \simeq -1.96_{-0.08}^{+0.09}$ and a turnover at $\log (M_T/\text{M}_{\odot})\simeq 7.10_{-0.56}^{+0.17}$ with a curvature of $\beta \simeq 1.00_{-0.73}^{+0.87}$ for our minimum assumption model with constant star formation history (SFH) and low dust attenuation, AV ≤ 0.2. We find that the z ∼ 6−7 GSMF, in particular its very low mass end, is significantly affected by the assumed functional form of the star formation history and the degeneracy between stellar mass and dust attenuation. For example, the low-mass end slope ranges from $\alpha \simeq -1.82_{-0.07}^{+0.08}$ for an exponentially rising SFH to $\alpha \simeq -2.34_{-0.10}^{+0.11}$ when allowing AV of up to 3.25. Future observations at longer wavelengths and higher angular resolution with the James Webb Space Telescope are required to break these degeneracies and to robustly constrain the stellar mass of galaxies on the extreme low-mass end of the GSMF.

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The evolution of the stellar mass function in star clusters

Astronomy and Astrophysics ◽

10.1051/0004-6361/200913325 ◽

2009 ◽

Vol 507 (3) ◽

pp. 1409-1423 ◽

Cited By ~ 58

Author(s):

J. M. D. Kruijssen

Keyword(s):

Star Clusters ◽

Mass Function ◽

Stellar Mass

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Erratum: Deconstructing the Galaxy stellar mass function with UKIDSS and CANDELS: the impact of colour, structure and environment

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stw390 ◽

2016 ◽

Vol 458 (4) ◽

pp. 3478-3478 ◽

Cited By ~ 1

Author(s):

Alice Mortlock ◽

Christopher. J. Conselice ◽

William G. Hartley ◽

Ken Duncan ◽

Caterina Lani ◽

...

Keyword(s):

Mass Function ◽

Stellar Mass ◽

The Galaxy ◽

The Impact

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The emergence of the galactic stellar mass function from a non-universal IMF in clusters

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732490 ◽

2018 ◽

Vol 614 ◽

pp. A43 ◽

Cited By ~ 4

Author(s):

Sami Dib ◽

Shantanu Basu

Keyword(s):

Mass Range ◽

Mass Function ◽

Stellar Mass ◽

Stellar Clusters ◽

Galactic Clusters ◽

Power Law Function ◽

Low Mass ◽

Mass Functions ◽

Characteristic Mass ◽

The Imf

We investigate the dependence of a single-generation galactic mass function (SGMF) on variations in the initial stellar mass functions (IMF) of stellar clusters. We show that cluster-to-cluster variations of the IMF lead to a multi-component SGMF where each component in a given mass range can be described by a distinct power-law function. We also show that a dispersion of ≈0.3 M⊙ in the characteristic mass of the IMF, as observed for young Galactic clusters, leads to a low-mass slope of the SGMF that matches the observed Galactic stellar mass function even when the IMFs in the low-mass end of individual clusters are much steeper.

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Correlations between H α equivalent width and galaxy properties at z = 0.47: Physical or selection-driven?

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab778 ◽

2021 ◽

Vol 503 (4) ◽

pp. 5115-5133

Author(s):

A A Khostovan ◽

S Malhotra ◽

J E Rhoads ◽

S Harish ◽

C Jiang ◽

...

Keyword(s):

Star Formation ◽

Equivalent Width ◽

Luminosity Function ◽

Mass Function ◽

Stellar Mass ◽

High Mass ◽

Selection Effects ◽

Star Formation Activity ◽

Low Mass ◽

Stellar Masses

ABSTRACT The H α equivalent width (EW) is an observational proxy for specific star formation rate (sSFR) and a tracer of episodic, bursty star-formation activity. Previous assessments show that the H α EW strongly anticorrelates with stellar mass as M−0.25 similar to the sSFR – stellar mass relation. However, such a correlation could be driven or even formed by selection effects. In this study, we investigate how H α EW distributions correlate with physical properties of galaxies and how selection biases could alter such correlations using a z = 0.47 narrow-band-selected sample of 1572 H α emitters from the Ly α Galaxies in the Epoch of Reionization (LAGER) survey as our observational case study. The sample covers a 3 deg2 area of COSMOS with a survey comoving volume of 1.1 × 105 Mpc3. We assume an intrinsic EW distribution to form mock samples of H α emitters and propagate the selection criteria to match observations, giving us control on how selection biases can affect the underlying results. We find that H α EW intrinsically correlates with stellar mass as W0∝M−0.16 ± 0.03 and decreases by a factor of ∼3 from 107 M⊙ to 1010 M⊙, while not correcting for selection effects steepens the correlation as M−0.25 ± 0.04. We find low-mass H α emitters to be ∼320 times more likely to have rest-frame EW>200 Å compared to high-mass H α emitters. Combining the intrinsic W0–stellar mass correlation with an observed stellar mass function correctly reproduces the observed H α luminosity function, while not correcting for selection effects underestimates the number of bright emitters. This suggests that the W0–stellar mass correlation when corrected for selection effects is physically significant and reproduces three statistical distributions of galaxy populations (line luminosity function, stellar mass function, EW distribution). At lower stellar masses, we find there are more high-EW outliers compared to high stellar masses, even after we take into account selection effects. Our results suggest that high sSFR outliers indicative of bursty star formation activity are intrinsically more prevalent in low-mass H α emitters and not a byproduct of selection effects.

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Erratum: “A High-resolution Multiband Survey of Westerlund 2 with the Hubble Space Telescope. III. The Present-day Stellar Mass Function” (2017, AJ, 153, 122)

The Astronomical Journal ◽

10.3847/1538-3881/ab701f ◽

2020 ◽

Vol 159 (3) ◽

pp. 127

Author(s):

Peter Zeidler ◽

Antonella Nota ◽

Eva K. Grebel ◽

Elena Sabbi ◽

Anna Pasquali ◽

...

Keyword(s):

High Resolution ◽

Hubble Space Telescope ◽

Mass Function ◽

Stellar Mass ◽

Space Telescope

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Photometric, kinematic, and variability study in the young open cluster NGC 1960

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa029 ◽

2020 ◽

Vol 492 (3) ◽

pp. 3602-3621 ◽

Cited By ~ 4

Author(s):

Y C Joshi ◽

J Maurya ◽

A A John ◽

A Panchal ◽

S Joshi ◽

...

Keyword(s):

Open Cluster ◽

Mass Range ◽

Mass Function ◽

Variable Stars ◽

B Stars ◽

V Band ◽

Short Period ◽

Young Open Cluster ◽

Mass Segregation ◽

Variability Study

ABSTRACT We present a comprehensive photometric analysis of a young open cluster NGC 1960 (= M36) along with the long-term variability study of this cluster. Based on the kinematic data of Gaia DR2, the membership probabilities of 3871 stars are ascertained in the cluster field among which 262 stars are found to be cluster members. Considering the kinematic and trigonometric measurements of the cluster members, we estimate a mean cluster parallax of 0.86 ± 0.05 mas and mean proper motions of μRA = −0.143 ± 0.008 mas yr−1 and μDec. = −3.395 ± 0.008 mas yr−1. We obtain basic parameters of the cluster such as E(B − V) = 0.24 ± 0.02 mag, log(Age/yr) = 7.44 ± 0.02, and d = 1.17 ± 0.06 kpc. The mass function slope in the cluster for the stars in the mass range of 0.72–7.32 M⊙ is found to be γ = −1.26 ± 0.19. We find that mass segregation is still taking place in the cluster which is yet to be dynamically relaxed. This work also presents first high-precision variability survey in the central 13 arcmin × 13 arcmin region of the cluster. The V-band photometric data accumulated on 43 nights over a period of more than 3 yr reveals 76 variable stars among which 72 are periodic variables. Among them, 59 are short period (P < 1 d) and 13 are long period (P > 1 d). The variable stars have V magnitudes ranging between 9.1 to 19.4 mag and periods between 41 min and 10.74 d. On the basis of their locations in the H–R diagram, periods, and characteristic light curves, 20 periodic variables belong to the cluster are classified as 2 δ-Scuti, 3 γ-Dor, 2 slowly pulsating B stars, 5 rotational variables, 2 non-pulsating B stars, and 6 as miscellaneous variables.

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