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 Stellar IMF at Low Masses 30 June 2015

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

M ( M  ) d log N d log M Extragalactic IMF concerns ?? ≠

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

La Barbera et al  (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 IMF vs. 

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

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

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

LRIS spectra arXiv:

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

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

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

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

IMF and/or abundance gradients ? arXiv: NGC 1023

IMF and/or abundance gradients ? arXiv: NGC 1023

IMF and/or abundance gradients ? arXiv: NGC 2974

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

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

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

Ongoing work: gradients at low and high 

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?

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