DEEP<i>HST</i>/ACS PHOTOMETRY OF THE M81 HALO

Durrell, Patrick R.; Sarajedini, Ata; Chandar, Rupali

doi:10.1088/0004-637x/718/2/1118

Cited by 39 publications

(40 citation statements)

References 94 publications

(163 reference statements)

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“…: MW : (Ryan & Norris 1991;An et al 2012); M31: (Durrell et al 2001(Durrell et al , 2004Chapman et al 2006;Kalirai et al 2006;Gilbert et al 2014;Ibata et al 2014;Gregersen et al 2015); M81: (Durrell et al 2010); NGC 891: (Mouhcine et al 2007;Rejkuba et al 2009); NGC 2403: (Barker et al 2012); Sombrero: (Mould & Spitler 2010); other nearby spirals (e.g. Mouhcine et al 2005;Mouhcine 2006); NGC 5128: (Harris et al 1999;Harris & Harris 2000Rejkuba et al 2005;Crnojević et al 2013;Rejkuba et al 2014); NGC 3377: (Harris et al 2007a) NGC 3379: (Harris et al 2007b;Lee & Jang 2016) NGC 3115: (Peacock et al 2015).…”

Section: Observed Metallicity Distribution Functions (Mdf) Of Clustermentioning

confidence: 97%

The difference in metallicity distribution functions of halo stars and globular clusters as a function of galaxy type

Lamers

Kruijssen

Bastian

et al. 2017

A&A

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Context. Observations of globular clusters (GCs) and field stars in the halos of the giant elliptical galaxy Cen A and the spiral galaxy M31 show a large range of cluster-to-star number ratios (or 'specific frequencies'). The cluster-to-star ratio decreases with increasing metallicity by over a factor of 100-1000, at all galactocentric radii and with a slope that does not seem to depend on radius. In dwarf galaxies, the GCs are also more metal-poor than the field stars on average. These observations indicate a strong dependence of either the cluster formation efficiency and/or the cluster destruction rate on metallicity and environment. Aims. We aim to explain the observed trends by considering the various effects that influence the cluster-to-star ratio as a function of metallicity, environment and cosmological history. Methods. We discuss the following effects that may influence the observed cluster-to-star ratio: (a) the formation efficiency of GCs; (b) the destruction of embedded GCs by gas expulsion; (c) the maximum masses of GCs; (d) the destruction of GCs by tidal stripping, dynamical friction, and tidal shocks as a function of environment; (e) the hierarchical assembly of GC systems during galaxy formation and the dependence on metallicity. Results. We show that both the cluster formation efficiency and the maximum cluster mass increase with metallicity, so they cannot explain the observed trend. Destruction of GCs by tidal stripping and dynamical friction destroy clusters mostly within the inner few kpc, whereas the cluster-to-star ratio trend is observed over a much larger range of galactocentric radii. We show that cluster destruction by tidal shocks from giant molecular clouds in the high-density formation environments of GCs becomes increasingly efficient towards high galaxy masses and, hence, towards high metallicities. The predicted cluster-to-star ratio decreases by a factor 100-1000 towards high metallicities and should only weakly depend on galactocentric radius due to orbital mixing during hierarchical galaxy merging, consistent with the observations. Conclusions. The observed, strong dependence of the cluster-to-star ratio on metallicity and the independence of its slope on galactocentric radius can be explained by cluster destruction and hierarchical galaxy growth. During galaxy assembly, GC metallicities remain a good tracer of the host galaxy masses in which the GCs formed and experienced most of their destruction. As a result, we find that the metallicity-dependence of the cluster-to-star ratio does not reflect a GC formation efficiency, but a survival fraction.

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Section: Observed Metallicity Distribution Functions (Mdf) Of Clustermentioning

confidence: 97%

The difference in metallicity distribution functions of halo stars and globular clusters as a function of galaxy type

Lamers

Kruijssen

Bastian

et al. 2017

A&A

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“…Many authors have adopted the view that this two-part structure of the MDF is evidence of two major and perhaps distinct starforming epochs in the formation histories of large galaxies, a view that has persisted for many years (e.g., Zepf & Ashman 1993;Forbes et al 1997Forbes et al , 2011Arnold et al 2011;Blom et al 2012b;Brodie et al 2014;Cantiello et al 2014;Kartha et al 2016, among many others). However, bimodal MDFs are not characteristic of the field-halo stars in their parent galaxies, in the few cases where it has been possible to directly compare the GCs and halo stars in the same galaxy (e.g., Harris et al 2007;Durrell et al 2010;Rejkuba et al 2011Rejkuba et al , 2014Monachesi et al 2016). Reconciling this apparent mismatch between field stars and GCs presents an intriguing challenge for quantitative formation modeling.…”

Section: Metallicity and Color Distributionsmentioning

confidence: 99%

Globular Cluster Systems in Brightest Cluster Galaxies. Iii. Beyond Bimodality

Harris

Ciccone

Eadie

et al. 2017

ApJ

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We present new deep photometry of the rich globular cluster (GC) systems around the Brightest Cluster Galaxies UGC 9799 (Abell 2052) and UGC 10143 (Abell 2147), obtained with the Hubble Space Telescope (HST) ACS and WFC3 cameras. For comparison, we also present new reductions of similar HST/ACS data for the Coma supergiants NGC 4874 and 4889. All four of these galaxies have huge cluster populations (to the radial limits of our data, comprising from 12,000 to 23,000 clusters per galaxy). The metallicity distribution functions (MDFs) of the GCs can still be matched by a bimodal-Gaussian form where the metal-rich and metalpoor modes are separated by 0.8 dex, but the internal dispersions of each mode are so large that the total MDF becomes very broad and nearly continuous from [Fe/H];−2.4 to solar. There are, however, significant differences between galaxies in the relative numbers of metal-rich clusters, suggesting that they underwent significantly different histories of mergers with massive gas-rich halos. Last, the proportion of metal-poor GCs rises especially rapidly outside projected radii  R R 4 eff , suggesting the importance of accreted dwarf satellites in the outer halo. Comprehensive models for the formation of GCs as part of the hierarchical formation of their parent galaxies will be needed to trace the systematic change in structure of the MDF with galaxy mass, from the distinctly bimodal form in smaller galaxies up to the broad continuum that we see in the very largest systems.

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“…2). In addition the RC mean colour and magnitude depend on the age and metallicity of the stars (Girardi & Salaris 2001), although the magnitude of the RC is more sensitive to age rather than to metallicity (Durrell et al 2010), and its colour, for stars older than 2 Gyr, is mainly sensitive to metallicity variations (Girardi & Salaris 2001). We use these properties of the RC feature to constrain the age and metallicity of these stars in the different fields (see Sect.…”

Section: Colour-magnitude Diagramsmentioning

confidence: 99%

“…As mentioned in Sect. 3.1, any variations in the RGB colour and slope are more sensitive to metallicity; the magnitude of the RC has a stronger dependence on age (Durrell et al 2010), while the colour of the RC for ages older than 2 Gyr is more sensitive to metallicity variations (Girardi & Salaris 2001). Bearing this in mind, we can use these features to perform a qualitative inspection of the CMDs at different radii to estimate the mean properties of the stellar populations as we proceed to larger galactocentric distances.…”

Section: Constraints On the Age And Metallicity Of The Stellar Populamentioning

confidence: 99%

Stellar structures in the outer regions of M 33

Grossi

Hwang

Corbelli

et al. 2011

A&A

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Aims. We present Subaru/Suprime-Cam deep V and I imaging of seven fields in the outer regions of M 33. Our aim is to search for stellar structures corresponding to extended Hi clouds found in a recent 21-cm survey of the galaxy. Three fields probe a large Hi complex to the southeastern (SE) side of the galaxy. An additional three fields cover the northwestern (NW) side of the galaxy along the Hi warp. A final target field was chosen further north, at a projected distance of approximately 25 kpc, to study part of the large stellar plume recently discovered around M 33. Methods. We analyse the stellar population at R > 10 kpc by means of V, I colour magnitude diagrams reaching the red clump. We constrain the age and metallicity of the different stellar populations, search for density enhancements that correspond to the Hi features, and investigate the radial surface distribution of the stars. Results. We find evolved stellar populations in all fields out to 120 (∼30 kpc), while a diffuse population of young stars (∼200 Myr) is detected out to a galactocentric radius of 15 kpc. The mean metallicity in the southern fields remains approximately constant at [M/H] = -0.7 beyond the edge of the optical disc, from 40 out to 80 . Along the northern fields probing the outer Hi disc, we also find a metallicity of [M/H] = -0.7 between 35 and 70 from the centre, which decreases to [M/H] = -1.0 at larger angular radii out to 120 . In the northernmost field, outside the disc extent, the stellar population of the large stellar plume possibly related to a M 33-M 31 interaction is on average more metal-poor ([M/H] = -1.3) and older ( ∼ >6 Gyr).Conclusions. An exponential disc with a large scale-length (∼7 kpc) fits well the average distribution of stars detected in both the SE and NW regions from a galactocentric distance of 11 kpc out to 30 kpc. The stellar disc extends beyond the Hi disc. The stellar distribution at large radii is disturbed and, although there is no clear correlation between the stellar substructures and the location of the Hi clouds, this gives evidence of tidal interaction or accretion events.

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DEEPHST/ACS PHOTOMETRY OF THE M81 HALO

Cited by 39 publications

References 94 publications

The difference in metallicity distribution functions of halo stars and globular clusters as a function of galaxy type

The difference in metallicity distribution functions of halo stars and globular clusters as a function of galaxy type

Globular Cluster Systems in Brightest Cluster Galaxies. Iii. Beyond Bimodality

Stellar structures in the outer regions of M 33

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