Compact Star Clusters in the M31 Disk

Vansevičius, Vladas; Kodaira, Keiichi; Narbutis, D.; Stonkutė, R.; Bridžius, A.; Deveikis, V.; Semionov, D.

doi:10.1088/0004-637x/703/2/1872

Cited by 34 publications

(75 citation statements)

References 65 publications

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“…First, these two studies were both significantly limited by the low-mass completeness cutoffs of their catalogs. Vansevičius et al (2009) and Caldwell et al (2009) have 50% completeness limits at log(M/M ) of 3.7 and 4.0, respectively, which is comparable to the M c value we measured for PHAT. Without a full accounting of the cluster population at masses below the knee of the distribution, it is difficult to properly constrain the characteristic truncation mass.…”

Section: Comparison To Previous Worksupporting

confidence: 85%

See 1 more Smart Citation

Panchromatic Hubble Andromeda Treasury. XVIII. The High-mass Truncation of the Star Cluster Mass Function

Johnson

Seth

Dalcanton

et al. 2017

ApJ

106

175

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We measure the mass function for a sample of 840 young star clusters with ages between 10-300 Myr observed by the Panchromatic Hubble Andromeda Treasury (PHAT) survey in M31. The data show clear evidence of a high-mass truncation: only 15 clusters more massive than > 10 4 M are observed, compared to ∼100 expected for a canonical M −2 pure power-law mass function with the same total number of clusters above the catalog completeness limit. Adopting a Schechter function parameterization, we fit a characteristic truncation mass of M c = 8.53 M . While previous studies have measured cluster mass function truncations, the characteristic truncation mass we measure is the lowest ever reported. Combining this M31 measurement with previous results, we find that the cluster mass function truncation correlates strongly with the characteristic star formation rate surface density of the host galaxy, where M c ∝ Σ SFR ∼1.1 . We also find evidence that suggests the observed M c -Σ SFR relation also applies to globular clusters, linking the two populations via a common formation pathway. If so, globular cluster mass functions could be useful tools for constraining the star formation properties of their progenitor host galaxies in the early Universe. Subject headings: galaxies: star clusters: general -galaxies: star formation -galaxies: individual (M31) -globular clusters: general 1. INTRODUCTION Star cluster populations are observational tracers of star formation activity in galaxies out to ∼100 Mpc distances. By comparing the properties of star cluster populations to the properties of overall star formation activity, studies of nearby galaxies have established that there is a correlation between the star formation rate (SFR) surface density, Σ SFR , and the fraction of stars that form in long-lived star clusters (e.g., Adamo et al. 2015, Johnson et al. 2016. This correlation demonstrates a close connection between star clusters and their formation environment, where the rate of cluster formation is linked to the total SFR, but also to local galactic properties such as gas surface density and interstellar pressure (Kruijssen 2012). One implication of this result is that star clusters can reveal the characteristics of past star formation episodes long after they have ended. While cluster destruction through evaporation due to two-body relaxation, tidal shocks, and other processes will erode lowmass star cluster populations over time, globular clusters and other massive clusters provide long-lived records of star formation activity.The mass function of star clusters is another observable property that we can exploit to study episodes of past star formation. Numerous studies have characterized the mass function of young star clusters using a power-law distribution (dN/dM ∝ M α ) with an index of α=−2.0 ± 0.3 that holds over a wide range of cluster

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Section: Comparison To Previous Worksupporting

confidence: 85%

“…For example, Vansevičius et al (2009) There are a number of points to consider when comparing our PHAT results to the work of Vansevičius et al (2009) andCaldwell et al (2009). First, these two studies were both significantly limited by the low-mass completeness cutoffs of their catalogs.…”

Section: Comparison To Previous Workmentioning

confidence: 99%

Panchromatic Hubble Andromeda Treasury. XVIII. The High-mass Truncation of the Star Cluster Mass Function

Johnson

Seth

Dalcanton

et al. 2017

ApJ

106

175

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“…Hence we see here that the cluster sample is dominated by the magnitude fading until log 10 (t/yr) ∼ 8.5 and that after the cluster disruption phase takes over. This typical lifetime scale is comparable to that derived for the star cluster population in the southwest field of the M 31 galaxy by Vansevičius et al (2009) using a star cluster sample photometry from Narbutis et al (2008).…”

Section: Derived Physical Parameters Of Clusterssupporting

confidence: 79%

“…We generated a sample of 10 000 artificial star clusters. The differential age distribution of the artificial clusters was chosen to mimic a two-slope profile similar to that described in Vansevičius et al (2009) for M 31 star clusters (see their Fig. 5a, reproduced in our Fig.…”

Section: Artificial Testsmentioning

confidence: 99%

Deriving physical parameters of unresolved star clusters

Meulenaer

Narbutis

Mineikis

et al. 2015

A&A

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Context. When trying to derive the star cluster physical parameters of the M 33 galaxy using broad-band unresolved ground-based photometry, previous studies mainly made use of simple stellar population models, shown in the recent years to be oversimplified. Aims. In this study, we aim to derive the star cluster physical parameters (age, mass, and extinction; metallicity is assumed to be LMC-like for clusters with age below 1 Gyr and left free for older clusters) of this galaxy using models that take stochastic dispersion of cluster integrated colors into account. Methods. We use three recently published M 33 catalogs of cluster optical broad-band photometry in standard UBVRI and in CFHT/MegaCam u * g r i z photometric systems. We also use near-infrared JHK photometry that we derive from deep 2MASS images. We derive the cluster parameters using a method that takes into account the stochasticity problem, presented in previous papers of this series. Results. The derived differential age distribution of the M 33 cluster population is composed of a two-slope profile indicating that the number of clusters decreases when age gets older. The first slope is interpreted as the evolutionary fading phase of the cluster magnitudes, and the second slope as the cluster disruption. The threshold between these two phases occurs at ∼300 Myr, comparable to what is observed in the M 31 galaxy. We also model by use of artificial clusters the ability of the cluster physical parameter derivation method to correctly derive the two-slope profile for different photometric systems tested.

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“…M 31 YMCs like those studied here provide also an excellent tracer of the disk kinematics in that galaxy, independent of (and in addition to) the HI gas. Recent wide-field surveys (Vansevicius et al 2009; see also Pap-II) suggest that a rich harvest of genuine YMCs await to be discovered in the disk of our next neighbor giant galaxy in Andromeda. i.e.…”

Section: Final Remarksmentioning

confidence: 99%

An HST/WFPC2 survey of bright young clusters in M 31

Perina

Cohen²,

Barmby

et al. 2010

A&A

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Aims. We present the main results of an imaging survey of possible young massive clusters (YMC) in M 31 performed with the Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST), with the aim of estimating their age and their mass. We obtained shallow (to B ∼ 25) photometry of individual stars in 19 clusters (of the 20 targets of the survey). We present the images and color magnitude diagrams (CMDs) of all of our targets. Methods. Point spread function fitting photometry of individual stars was obtained for all the WFPC2 images of the target clusters, and the completeness of the final samples was estimated using extensive sets of artificial stars experiments. The reddening, age, and metallicity of the clusters were estimated by comparing the observed CMDs and luminosity functions (LFs) with theoretical models. Stellar masses were estimated by comparison with theoretical models in the log(Age) vs. absolute integrated magnitude plane, using ages estimated from our CMDs and integrated J, H, K magnitudes from 2MASS-6X. Results. Nineteen of the twenty surveyed candidates were confirmed to be real star clusters, while one turned out to be a bright star. Three of the clusters were found not to be good YMC candidates from newly available integrated spectroscopy and were in fact found to be old from their CMD. Of the remaining sixteen clusters, fourteen have ages between 25 Myr and 280 Myr, two have older ages than 500 Myr (lower limits). By including ten other YMC with HST photometry from the literature, we assembled a sample of 25 clusters younger than 1 Gyr, with mass ranging from 0.6 × 10 4 M to 6 × 10 4 M , with an average of ∼3 × 10 4 M . Our estimates of ages and masses well agree with recent independent studies based on integrated spectra. Conclusions. The clusters considered here are confirmed to have masses significantly higher than Galactic open clusters (OC) in the same age range. Our analysis indicates that YMCs are relatively common in all the largest star-forming galaxies of the Local Group, while the lack of known YMC older than 20 Myr in the Milky Way may stem from selection effects.

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Compact Star Clusters in the M31 Disk

Cited by 34 publications

References 65 publications

Panchromatic Hubble Andromeda Treasury. XVIII. The High-mass Truncation of the Star Cluster Mass Function

Panchromatic Hubble Andromeda Treasury. XVIII. The High-mass Truncation of the Star Cluster Mass Function

Deriving physical parameters of unresolved star clusters

An HST/WFPC2 survey of bright young clusters in M 31

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