The Optical Colors of Giant Ellipticals and their Metal-Rich GCs Indicate a Bottom-Heavy IMF at Sub-Solar Masses (for R gal < R eff ) Paul Goudfrooij (STScI) and Diederik Kruijssen (MPA) ApJ, 762, 107 (2013) ; ApJ, 780, 43 (2014)

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Model-Independent Approach: Colors of Metal-Rich GCs vs. of Host Galaxies Peng et al. (2006) (Virgo ACS Survey) Stars form in clustered fashion (e.g., Lada & Lada 2003), then disperse due to dynamical evolution Bimodal GC color distribution very common in giant early- type galaxies Mainly due to Metallicity Strong connection between Red subpopulation (number and mean color) and host galaxy Red GCs associated with “bulge” component

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Stars form in clustered fashion (e.g., Lada & Lada 2003), then disperse due to dynamical evolution Bimodal GC color distribution very common in giant early- type galaxies Mainly due to Metallicity Strong connection between Red subpopulation (number and mean color) and host galaxy Red GCs associated with “bulge” component Peng et al. (2006) (Virgo ACS Survey) Model-Independent Approach: Colors of Metal-Rich GCs vs. of Host Galaxies Progenitor galaxies thought to have had SFR > 10 2 M  /yr, likely at high pressure

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI ACS Ground-based NGC 3610 Radial Distribution of Blue and Red GCs Radial distribution of red GCs matches that of “bulge” light –“Surviving” star clusters from SF events that also formed bulge Blue GCs more extended “halo” distribution Goudfrooij et al. (2007) Forbes et al. (2012) Galaxy light Red GCs

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Age & Metallicity of Average Red GC Consistent with Parent Galaxy (1) Lick indices H  and [MgFe] ’ for massive blue and red GCs in M49 (data from Cohen et al. 2003; SSP model of Thomas et al. 2003) Average red GC same EWs as galaxy at same R gal (galaxy data: Davies et al. 1993; Fisher et al. 1995) [Z/H] = − 0.03 on Zinn & West (1984) scale av. red GC galaxy

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Age & Metallicity of Average Red GC Consistent with Parent Galaxy (2) NGC 1407: Same situation GC data: Cenarro et al. (2007); galaxy data: Spolaor et al. (2008). More galaxy+GC data please? (at a given R gal ) av. red GC galaxy

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Colors of Massive Red GCs vs. of their Parent Giant Ellipticals Galaxies systematically redder by 0.13 − 0.20 mag in inner regions (10σ − 25σ) Age / Z effect?  Not according to spectroscopy, nor expected if GCs and field stars were formed together Effect of multiple stellar populations in massive GCs? Goudfrooij & Kruijssen (2013) Data: ACS Virgo Cluster Survey (Jordan et al. 2009) 2 Solid line: Diffuse light of parent gE Red circles: GCs in red peak with log M/M  > 5.3 Dashed line: Weighted fit to red GCs

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI The effect of multiple stellar pops to integrated colors of GCs (1) Building Kurucz stellar atmosphere models to simulate integrated-light spectra of populations ATLAS12 + SYNTHE spectra of 1 st and 2 nd gen. stars Using abundance patterns seen in massive MW GCs Pop. Y[C/Fe][N/Fe][O/Fe] [Na/Fe ] 1 st Z nd 0.35− −

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI The effect of multiple stellar pops to integrated colors of GCs (2) Magnitude differences ΔBC as function of log(g) Strong effects in u SDSS and U J, (much) weaker at longer λ Interestingly, averaging over Salpeter IMF yields very small color offsets In particular, Δ(g-z) = and Δ(B-I) = Details in Goudfrooij & Kruijssen (2013, ApJ, 762, 107)

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI The effect of multiple stellar pops to integrated colors of GCs (4) Chung et al. (2011): Model w/He enhancement to explain UV Upturn phenomenon UV upturn explained by He-enriched EHB stars ~10 4 K hotter than “normal” HB stars

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI The effect of multiple stellar pops to integrated colors of GCs (5) Chung et al. (2011): Model w/He enhancement to explain UV Upturn phenomenon UV upturn explained by He-enriched EHB stars ~10 4 K hotter than “normal” HB stars Good fit to UV-bright GCs in M87 Effect to integrated Δ(g-z) < 0.015, Δ(B-I) < 0.020

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Colors of Massive Red GCs vs. of their Parent Giant Ellipticals Galaxies systematically redder by 0.13 − 0.20 mag in inner regions (10σ − 25σ) Age / Z effect?  Not according to spectroscopy, nor expected if GCs and field stars were formed together Effect of multiple stellar populations in massive GCs?  NO (i.e., insignificant): Δ(g-z) ≤ 0.04 mag Different stellar mass functions? Goudfrooij & Kruijssen (2013) Data: ACS Virgo Cluster Survey (Jordan et al. 2009) 2 Solid line: Diffuse light of parent gE Red circles: GCs in red peak with log M/M  > 5.3 Dashed line: Weighted fit to red GCs

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Colors of Massive Red GCs vs. of their Parent Giant Ellipticals Define dN/dM = a M + α (sorry) Using  ( M > 0.8 M  ) = −2.35 (Salpeter) &&  ( M ≤ 0.8 M  ) =  MF Δ (g−z) consistent with steep IMF (  ~ −2.8) in field stars and “normal” MF in average massive GC Goudfrooij & Kruijssen 2013; Data: ACS Virgo Cluster Survey; Marigo et al. (2008) isochrones

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Consistency with H β  and [MgFe]’ Steep IMF at sub-solar masses has ~no impact on Hβ and [MgFe]’ for old populations

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Effect of Dynamical Evolution to GC MFs as function of IMF shape Kroupa MF M GC

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Effects of IMF and GC Mass Loss to ‘blue tilt’ and ‘red tilt’ Goudfrooij & Kruijssen (2014): Effect of dynamical evolution to GC colors M GC Kroupa MF Marigo et al. (2008) isochrones

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Effects of IMF and GC Mass Loss to ‘blue tilt’ and ‘red tilt’ Goudfrooij & Kruijssen (2014): Effect of dynamical evolution to GC colors M GC Kroupa MF Mieske et al. (2010): Color-Magnitude Relation among GCs in ACSVCS and ACSFCS surveys (~ 16,900 GCs!)  Shallow red tilt exists in high- mass Es Marigo et al. (2008) isochrones

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Effects of IMF and GC Mass Loss to ‘blue tilt’ and ‘red tilt’ Goudfrooij & Kruijssen (2014): Effect of dynamical evolution to GC colors Mieske et al. (2010) Blue and Red tilts (for high-mass Es) Modeled colors for [Z/H] = −1.3 and −0.3 M GC Kroupa MF

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Concluding Remarks Δ (g-z) between giant E galaxies and their massive metal-rich GCs at given R gal (< R e ) seems mainly due to bottom-heavy IMF  Spectroscopic mean ages/metallicities are same within small uncertainties  Effect of multiple stellar populations << Δ (g-z) observed  Bluer GC color consistent with long-term dynamical evolution Tilt in CMR of metal-rich GCs in gEs also best reproduced by bottom-heavy IMF ( α ≤ −2.3) Overall result seems to indicate steep IMF in inner regions of massive ellipticals.

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Possible reason for bottom-heavy IMF Hopkins (2013) Bottom-heavy IMF comes about at high turbulence (Mach number) and high surface density/SFE Fragmentation occurs at relatively small scales, set by sonic mass rather than Jeans mass, shifting the turnover mass to smaller values

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Colors of Massive Red GCs vs. of Parent Giant Ellipticals Goudfrooij & Kruijssen 2013a; Data: Forbes et al. (2006) and Spolaor et al. (2008); Marigo et al. (2008) isochrones Similar situation for NGC 1407 photometry

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Age & Metallicity of Average Red GC Consistent with Parent Galaxy (2) NGC 1407: Same situation GC data: Cenarro et al. (2007); galaxy data: Spolaor et al. (2008). No significant signature of Blue HB stars among metal-rich GCs (!) More galaxy+GC data please? (at a given R gal ) av. red GC galaxy

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI The effect of multiple stellar pops to integrated colors of GCs (3) NGC 6441 ([Z/H] = −0.4): Massive metal-rich GC with most developed blue HB known, thought due to high Y Finds Y (SG) = 0.35 with some trickling out to Y ≤ 0.40 N(BHB) < 0.07 N(RHB) Effect to integrated Δ(g-z) < 0.015, Δ(B-I) < Caloi & D’Antona (2007) Dotter et al. (2010)  N6441

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Effects of IMF and GC Mass Loss to ‘blue tilt’ and ‘red tilt’ Goudfrooij & Kruijssen (2014): Effect of dynamical evolution to GC colors −1.3 −0.3

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Effects of IMF and GC Mass Loss to ‘blue tilt’ and ‘red tilt’ Goudfrooij & Kruijssen (2014): Effect of GC mass loss to Blue/Red tilts Bailin & Harris (2009) default GC self- enrichment model: Self-enrichment when E bind ~ E SN Isothermal proto-GC cloud with r = 1 pc SFE: f ★ = 30% From Z to g-z color using Blakeslee et al. (2010) and Peng et al. (2006) relations (no significant differences) GC mass loss from K09 models (for age = 12 Gyr) Total stellar evolution mass loss depends on IMF (largest for bottom-light / Kroupa IMF) Dynamical evolution mass loss: (2-10) × 10 5 M  and only weakly dependent on IMF

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Effects of IMF and GC Mass Loss to ‘blue tilt’ and ‘red tilt’ Goudfrooij & Kruijssen (2014): Effect of GC mass loss to Blue/Red tilts Adding (mass- dependent) self- enrichment and MF effect on g-z color Blue tilt in gEs well- reproduced by “default” BH09 self- enrichment for all IMFs Red tilt in gEs best reproduced by α ≤ −2.35

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI GC Color-Magnitude Relation plots (1) Mieske et al. (2010)

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI GC Color-Magnitude Relation plots (2) Mieske et al. (2010)

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI GC Color-Magnitude Relation plots (3) Strader et al. (2006)

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Due in Part to SSP Model Inaccuracies? Strader et al., 2011, AJ 142, 8

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Effect on Cappellari et al. Result Cappellari et al., 2012, Nature 484, 485

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Significant Variations only in Subsolar Regime for Older Star Clusters Bastian, Covey, & Meyer, 2010, ARAA 48

June 30, 2015 Paul Goudfrooij Workshop on the Low-Mass IMF, STScI Effect of Dynamical Evolution to GC MFs as function of IMF shape