1. Jessica Lu (UH IfA) Andrew Mann (UT Austin) Radial trends in IMF-sensitive absorption features in two early-type galaxies: evidence for abundance-driven gradients Nicholas McConnell Parrent Postdoctoral Fellow University of Hawaii (IfA) arXiv 1506.07880 Stellar IMF at Low Masses 30 June 2015

2. IMF and/or abundance gradients ? arXiv: 1506.07880 NGC 1023 NGC 2974

3. M ( M  ) 0.1 1 10 100 d log N d log M 0.01 1.0 Extragalactic IMF concerns ?? ≠

4. z = 2 z = 0 Hopkins et al. 2010 van Dokkum et al. 2010 z = 0 z = 0.6 z = 1.1 z = 1.6 z = 2.0 log(r)  Inside-out growth stellar population gradients

5. La Barbera et al. 2013 100 300150 200 250  (km/s) Conroy & van Dokkum 2012b Aperture = 1/8 r eff Aperture = 3” (mix of r/r eff ) Aperture ~ 1 r eff McDermid et al. 2014 IMF vs. 

6. Conroy & van Dokkum 2012b IMF-sensitive spectral features Keck + LRIS dwarf-sensitive giant-sensitive

7. Conroy & van Dokkum 2012a Chabrier x = 3 Interpreting the IMF from galaxy spectra NGC 1023: central 0.7 ’’ x 1.0 ’’ (Keck LRIS) dwarf-sensitive giant-sensitive

8. LRIS observations van Dokkum & Conroy (2012)Gradient strategy science sky ( 1 frame) science sky ( 2 frames) r / r eff (e.g., Na strength)

9. LRIS spectra arXiv: 1506.07880

10. Galaxy spectra: radial variations arXiv: 1506.07880 NGC 1023 (convolved to  = 230 km/s) NGC 2974 (  = 245 km/s) Normalized Flux

11. Stellar Population Synthesis Spiniello et al. 2014 Colors Young to Old stars Symbols Solar to  super [  /Fe] * Feature Na 8190 Ca triplet Mg 8800 TiO 8900 W-F FeH

12. Na I 8190 Å (e.g., Conroy & van Dokkum 2012a) arXiv: 1506.07880 Telluric Absorption: ~ 5-15% error in Na index

13. Wing-Ford FeH (e.g., Conroy & van Dokkum 2012a) arXiv: 1506.07880

14. IMF and/or abundance gradients ? arXiv: 1506.07880 NGC 1023

15. IMF and/or abundance gradients ? arXiv: 1506.07880 NGC 1023

16. IMF and/or abundance gradients ? arXiv: 1506.07880 NGC 2974

17. arXiv: 1506.07880 IMF and/or abundance gradients: significance of 0.1 r eff ?

18. Martín-Navarro et al. 2015a also: Conroy & van Dokkum in prep. Zieleniewski et al. 2015 IMF and/or abundance gradients? Contemporary results

19. Martín-Navarro et al. 2015a Zieleniewski et al. 2015 Na I 8190 Å vs. Na D 5890 Å

20. Ongoing work: gradients at low and high 

21. Summary Metallicity gradients are just the first chapter Extreme populations occur inside ~ 0.1 r eff (~ 300 pc) Early-type galaxies have excess sodium, and probably nitrogen “IMF-sensitive” spectral features can behave inconsistently In progress: verify the above for N > 2 objects Open Q: how well must your favorite SPS model match your galaxy spectrum to convince you of an unusual IMF?

23. arXiv: 1506.07880 IMF and/or abundance gradients: significance of 0.1 r eff ?