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 ?