Do we know all the Milky Way Globular Clusters? Dirk Froebrich

Do we know all the Milky Way Globular Clusters? Dirk Froebrich

People 1) Candidates from the FSR Cluster Sample A. Scholz H. Meusinger C.J. Davis C.L. Raftery 2) Candidates from the GPS and Mercer list A. Longmore R. Kurtev T. Macarone P.W. Lucas V.D. Ivanov D. Minniti J. Borissova R. de Grijs

Known Galactic Globular Clusters 158 kown (pre FSR catalogue or 2007) Harris (1996, 2003) lists 150, + Glimpse-C01 (Kobulnicky et al. 2005), GC Whiting1 (Carraro et al. 2005), SDSS J1049+5103 SDSS J1257+3419 (Willman et al. 2005), AL3 (Ortolani et al. 2006), GC SEGUE1 (Belokurov et al. 2007), Koposov1 Koposov2 (Koposov et al. 2007)

Whybother? apparent difference in numbers of MW Globular Clusters compared to e.g. the Andromeda galaxy true or selection effect? study the formation and evolution of the Galaxy some GlCls are from captured dwarf galaxies probe the structure of the Galaxy

The FSR Cluster Sample

The FSR Cluster Sample Zone of Avoidance High extinction and star density low density contrast between cluster and background distant clusters are obscured by dust 10±3 GlCl are missing within 3kpc from the Galactic Center and near the Galactic Plane (Z<0.5kpc) (Ivanov et al. 2005) Froebrich et al. (2007)

The FSR Cluster Sample JHK star density maps 14400square degrees each 3.5 resolution 20 pixels 0.5GigaPixel images 120hours computing time on 16node double processor Beowulf-type cluster Froebrich et al. (2007)

The FSR Cluster Sample Search for local enhancements in JHK star density maps use SExtractor (Bertin & Arnouts 1996) 4σ above local (10 x5 ) noise and >11square arcmin + manual search cloud edges and spikes of bright stars rejected fainter objects with cluster like appearance added every cluster must be detected in H and (J or K) 2iterations between two people for validation! Froebrich et al. (2007)

The FSR Cluster Sample 1788 cluster candidates detected 782 automatically, 1006 manually ratio of auto/manu constant along Galactic Plane SIMBAD cross referencing: 86 known GlCl (out of 93 with d<17kpc in this area) 681 known OpCl 1021 new cluster candidates ~500 real new clusters

Classification King (1962) radial density profile Automatic fit at local completeness limit, excluding regions with source confusion (dense cluster centers) Manual verification of validity via majority decision Froebrich et al. (2007)

Classification P Op/Gl = N Op/Gl / (N Op + N Gl ) for each plot and cluster plot i Froebrich et al. (2007) /(681/86)

Classification new GlCl (85%) OpCl (95%) Froebrich et al. (2007)

Classification of Star Clusters C1716 Log(R N )=-0.060 Glimpse C01 Log(R N )=-0.851

Classification of Star Clusters C1735 Log(R N )=+0.238 Glimpse C01 Log(R N )=-0.851

The FSR Cluster Sample http://astro.kent.ac.uk/~df/clusters/index.html Froebrich et al. (2007)

The Mercer Cluster Sample 92 new clusters identified in GLIMPSE data Automatic detection based on Bayesian information criterion 59 detected only 6 of these detected in 2MASS automatically 24 show clustering visually 33 objects found by visual inspection of images Mercer et al. (2005)

FSR 1735 Froebrich et al. (2007b/2008b)

FSR 1735 ESO NTT

Fore/Background decontamination Stars in cells in J, (J-H) and (J-K) space in cluster and control field are counted and stars are randomly removed according to statistics (Bonatto & Bica 2007). Cells vary in size according to stellar density. Typically they are ΔJ=0.5mag, Δ(J-H)=0.2mag and Δ(J-K)=0.2mag.

Isochrone Fitting Froebrich et al. (2008b) Age>8Gyrs Ak=0.7mag d=7.0kpc [M/H]=-0.7

FSR 1716 Froebrich et al. (2008b)

FSR 1716 ESO NTT

Isochrone Fitting Froebrich et al. (2008b) Age>2Gyrs Ak=0.57mag d=7kpc [M/H]=-0.7±0.4

FSR 0584 Classified as probable Globular Cluster by Bica et al. (2007) based on 2MASS and proper motions

FSR0584 Bica et al. 2007, A&A, 472, 483 FSR0584 Log(R N )=+0.572 Based on JHK data and proper motions, its most probably a GlCl. Projected onto W3 cloud. The closest known GlCl! d=1.4kpc A V =9.2+-0.6mag R core =0.3+-0.1pc R tid =4.5+-0.5pc

FSR 1767 Classified as Globular Cluster by Bonatto et al. (2007) based on 2MASS and proper motions but Froebrich et al. (2008b)

FSR 1767 ESO NTT

Fore/Background decontamination

Isochrone Fitting Bonatto et al. (2007) Age=10Gyrs Ak=0.62mag d=1.5kpc [M/H]=-1.3

Isochrone Fitting Froebrich et al. (2008b) Age=1.25Gyrs Ak=0.4mag d=8.5kpc [M/H]=+0.0

Mercer 3 Kurtev et al. (2008)

Mercer 3 ESO NTT Kurtev et al. (2008)

Mercer 3 Kurtev et al. (2008), A&A, accepted or Strader & Kobulnicky (2008) subm. on astro-ph two days later... Kurtev et al. (2008) Age=??? Ak=2.7mag d=4.6kpc [Fe/H]=-0.33

Mercer 5 from Mercer et al. (2005), but independently found in UKIDSS quality control Longmore et al. (2009) in prep.

Mercer 5 ESO NTT +UKIDSS

Mercer5 Longmore et al. (2009) [Fe/H]=-0.94±0.16

Mercer5 Longmore et al. (2009) Age=??? Ak=1.1±0.1mag d=5-6kpc [Fe/H]=-0.94

Known Galactic Globular Clusters 161 + 2? kown 150 in Harris (1996, 2003) + Glimpse-C01 (Kobulnicky et al. 2005), GC Whiting1 (Carraro et al. 2005), SDSS J1049+5103/J1257+3419 (Willman et al. 2005), AL3 (Ortolani et al. 2006), GC SEGUE1 (Belokurov et al. 2007), Koposov1/2 (Koposov et al. 2007), FSR1735 (Froebrich et al. 2007b/2008b), FSR1767 (Bonatto et al. 2007), FSR0584? (Bica et al. 2007), FSR0190? (Froebrich et al. 2008c), FSR1716 (Froebrich et al. 2008b), Mercer3 (Kurtev et al. 2008), Mercer5 (Longmore et al. 2009)

Properties of new GlCls some part of the missing population within ~3kpc from the Galactic Centre (e.g. FSR1735, Mercer3, Mercer5)

Properties of new GlCls some part of the missing population within ~3kpc from the Galactic Centre (e.g. FSR1735, Mercer3, Mercer5) metallicities within [M/H] = -0.3... -1.0 at lower end of luminosity distribution Palomar GlCls

Do we know all the Milky Way Globular Clusters? Probably not, but: Further objects of the known cluster candidates from the FSR, Mercer and future GPS list might be classified as GlCl. There are no more obvious, overlooked objects in 2MASS and Glimpse. The lower end of the luminosity function is still incomplete.

Conclusions We have identified 1021 new star cluster candidates with b <20 in star density maps (40-50% contamination rate). Follow up observations/analyses have so far revealt 3 new galactic GlCl candidates from the FSR list (plus a number of old OpCl). At least deep NIR imaging is required to verify their nature. 2MASS alone is insufficient in some cases (e.g. FSR1767)! The Mercer list of clusters also revealt 2 GlCls so far. More, probably Palomar Type GlCls, are likely to be found amongst the FSR, Mercer, and GPS lists.