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First-­‐ and second-­‐genera/on dwarf galaxies in gas-­‐rich interac/ng groups Presented by: Karen Lee-­‐Waddell, PhD Candidate PHISCC 2015 In collabora8on with: K. Spekkens (RMC), M. P. Haynes (Cornell), P. Chandra (NCRA), J.-­‐C. Cuillandre (CFHT), N. N. Patra (NCRA), S. S8erwalt (UVa), J. Sick (Queen’s), J. Cannon (Macalester), R. Giovanelli (Cornell) Interac/ng Galaxies NGC 5426/7 (Gemini Observatory/
GMOS-­‐S/NSF) NGC 3808A/B (NASA/ESA/HST) UGC 8335 (NASA/ESA/HST/A. Evans) NGC 4038/9 (Star Shadows Remote Observatory/
PROMPT/CTIO/J. Harvey) Simula/ons of Interac/ons Standard cosmological simula8on (assuming DM) 250 Myr 400 Myr 800 Myr 150 Myr (Bournaud & Duc 2006) •  produce ≤2 long lived TDGs per merging event TDGs Simula/ons Bournaud & Duc (2006): •  96 simula8ons involving 184 spiral galaxies •  3.2 8dal substructures produces per parent galaxy (593 total) •  t = 500 Myr, 35% exist •  t = 2 Gyr, 20% remain (45% w/ M > 109 M¤) Fouquet et al. (2012): •  all major mergering events produce strong 8dal tails •  tails contain many (>10) large (M > 108 M¤) 8dal knots •  majority of knots survive over 9 Gyr (hidden slide) Significance of TDGs? Are TDGs the key to falsifying standard DM cosmology? DM-­‐free simula8on ≥5 TDGs at 9 Gyr f 3 TDGs in NGC 5291 (Kroupa 2012) (Fouquet et al. 2012) Significance of TDGs Standard Model: •  TDGs are occasionally produced during DM induced merging events •  TDGs cons8tute ~6% of nearby dwarf galaxies •  important in the understanding of galaxy evolu8on (Kaviraj et al. 2012) An Alterna8ve Model: •  all dwarf galaxies are decedents of long lived DM poor TDGs •  form DoS and VPOS •  DM is not necessary, ∴ DM does not exist •  key to falsifying DM cosmology (Kroupa 2012) (hidden slide) Dwarf Galaxy Survey Arecibo (arecibo-­‐observatory.org) GMRT (gmrt.ncra.8fr.res.in) CFHT (ckt.hawaii.edu) Unbiased HI census of gas-­‐rich dwarf galaxies NGC 3166/9 GMRT on CFHT NGC 3169 NGC 3166 NGC 3165 AGC 208537 AGC 208457 (Lee-­‐Waddell et al. 2012) NGC 871/6/7 GMRT on CFHT AGC 748853 AGC 748849 UGC 1761 NGC 877 NGC 871 NGC 876 AGC 749170 AGC 121467 (Lee-­‐Waddell et al. 2014) NGC 4725/47 GMRT on CFHT AGC 229104 NGC 4747 NGC 4725 (Lee-­‐Waddell et al. in prep) Tidal Detec/ons AGC 208457 AGC 749170 (Lee-­‐Waddell et al. 2012) AGC 229104 TDG candidate (Lee-­‐Waddell et al. 2014) op8cally dim 8dal feature (Lee-­‐Waddell et al. in prep) large 8dal knot Comparison to Other Dwarfs AGC 749170 i AGC 208457 g Comparison to Other Dwarfs AGC 749170 i jAGC 208457 (Kroupa 2012) Conclusions & Future Work •  one “galaxy-­‐like” 8dal feature per group •  first-­‐ and second-­‐genera8on gas-­‐rich dwarfs have observably variant proper8es •  improve sta8s8cs by observing more interac8ng groups •  metallicity informa8on to further differen8ate first-­‐ and second-­‐genera8on dwarfs