Stellar Population Mass Estimates Roelof de Jong (STScI AIP) Eric Bell (MPIA Univ. of Michigan)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Overview Stellar Mass-to-Light (M/L) ratios from SEDs Comparing different SED fitting techniques Comparing stellar population M/L values with dynamical and other techniques Conclusion: stellar population masses are remarkably consistent with dynamical estimates

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Galaxy evolution models ‣ Closed box models Mass dependent formation history with star bursts Bell & de Jong (2001)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Hierarchical formation models Most galaxy formation models show strong correlation between optical colors and M/L ratios Dust is in general also degenerate in the color- M/L relation Relation probably breaks down in the near-IR due to metallicity Cole et al. (2000) models B K I

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Single burst evolution Bruzual & Charlot (2003), Chabrier IMF

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Exponential Star Formation Rate Final age 12 Gyr

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Final age of exponential SFR model 12 Gyr 8.5 Gyr 6 Gyr 3 Gyr 2 Gyr Integrated SED does not have the information to tell 8 from 12 Gyr population

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Add starburst to exp. SFR model Starburst adds 10% to final mass 12 Gyr

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Different SSP models

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 IMF changes normalization

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Different Initial Mass Functions The slope of the color-M/L relation is independent of model or IMF used The normalization of the relation depends on the IMF used, i.e. the amount of low mass stars Bell & de Jong (2001)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Maximum disk normalization Color-M/L relation must be normalized below all maximum disk values Salpeter normalization if too massive Bell & de Jong (2001) use Salpeter decreased by 0.15 dex Salpeter Salpeter light data Verheijen (1997) Based on Key Project distance scale

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Comparing SED fitting methods Data SDSS and 2MASS Default model in comparisons: grid of exponential declining SFR fitted to ugrizK, Charlot & Bruzual models, Chabrier IMF (Bell et al. 2003, B03) color-M/L shows curvature; B03 grid limits Bell & de Jong (2001)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Exponential versus single bursts Large systematic offsets due to lack of old, low luminosity population Blanton & Roweis (2007)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Exponential versus double bursts Having young second burst does not solve the problem if the first burst is still quite young old: 0.64, 1, 2.5, 5, 11 Gyr young: 100 Myr full range of metallicities Kannappan & Gawiser (2007)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Small scatter but systematic offset with kcorrect (Blanton & Roweis 2007) Due to difference in star formation history in templates Exponential versus SFH templates Blanton & Roweis (2007) Peak SF at 6 Gyr at least 5x higher than at 12 Gyr

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Broadband versus spectra Spectra better at picking up recent burst Star formation history of templates all similar Kauffmann et al. (2003)Gavazzi et al. (2005)Panter et al. (2005)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Fitting comparison summary Star formation history of templates critical ‣ Probably should match SFH of Universe, but may depend on galaxy type IMF will give expected offsets at z=0, but redshift evolution will depend on IMF (e.g., Conroy et al. 2008) Fitting of spectra better for picking up recent bursts

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Comparing stellar pop M/L to gravity Constrain SED-M/L relation offset relative to Solar metalicity, exponentialy declining SFR models using Charlot & Bruzual (2003) with Chabrier IMF ‣ using simplest model to allow easy comparisons Assumptions made: ‣ IMFs are universal ‣ HST Key project distance scale ‣ No selective loss of stellar populations ‣ Simple dust corrections

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Globular cluster M/Ls: segregated mass loss M/L values of Globular Clusters often much lower than predicted by models Can be explained by mass segregation and subsequent stripping Makes interpretation model dependent Kruijssen (2008)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Elliptical galaxies Stellar population modeling of line indices Schwarzschild kinematic modeling Slow rotators may have 30% dark matter within Reff (or different IMF) Provides upper limit Cappellari et al. (2005)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Maximum disk rotation curves Upper limit improved by combining new samples Bell & de Jong (2001) Bell et al. (2003) de Jong Verheijen Kassin de Jong & Bell, in prep.

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Minimum bulge/disk rotation curves Inner part of rotation curve can only be explained if stellar components have a high enough M/L Noordermeer (2005)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Minimum bulge rotation curves Noordermeer PH.D. thesis results rather discouraging Noordermeer (2005) Bell & de Jong (2001)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Minimum bulge rotation curves Remove: ‣ near face-on systems ‣ non-declining curves ‣ improve colors using SDSS calibration results in lower limit that is at max ~0.1 dex lower than Bell & de Jong (2001) Bell & de Jong (2001) Bell et al. (2003) de Jong & Bell, in prep.

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Disk velocity dispersion: Bottema Improve Bottema by using up-to- date photometry (photographic B versus 2MASS J) This sample still mainly sub- maximal disks data Bottema (1995) de Jong & Bell, in prep.

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Disk velocity dispersion: Kregel Edge-on galaxies dynamical mass modeling from velocity dispersions Bell & de Jong (2001) Baryonic TF from dynamical modeling Assumed dispersion ratio scales with (M/L) 2 Kregel, van der Kruit & Freeman (2005)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Bar streaming motions Gas shock across bar depends critically on M/L Requires M/L higher than default model data Weiner et al. (2004)

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Summary M/L comparisons Distance uncertainties still critical, especially for methods based on a few galaxies Default model consistent with all gravity data Kroupa (2001) and Chabrier (2003) consistent, Kennicutt (1983) too low Role molecular gas?

Roelof de Jong | Unveiling the Mass | Kingston, June 15-19, 2009 Conclusions Choice of Star Formation Histories to use in SED fitting can lead to systematic offsets and scatter SED itself does not contain enough information to resolve this uncertainty, secondary arguments necessary Gives similar offsets as IMF variations Dynamical constraints from large range of techniques and objects suggests limited range of IMF and SFH combination applicable