A Survey of Neutral Hydrogen Properties of the NGC 5846 Group of and Its Environment Halley Darling ('13) Professor Koopmann, Summer '10

Abstract: Interactions between galaxies are thought to Contouring Neutral Hydrogen (HI) Detections: have an effect on how individual galaxies evolve. Neutral Extended View of the Region: hydrogen, or HI, supplies gas for star formation, and IDL programs developed at George Mason University by Nicolas studying its presence among members of a group or Crump and brought to Union by Ana Mikler ('12) The NGC 5775 group is one of several groups in close proximity to NGC cluster of galaxies can reveal the environment's effect on Shows HI data cumulatively over multiple frequencies/velocities 5846 as shown in Figure 3 using information collected from the NASA/IPAC galaxy evolution. We employ the ALFALFA neutral Extragalactic Database (NED). hydrogen survey to determine HI properties of the galaxy Allows direct comparison of HI to optical imaging from the Data processed during this research session, reveals the members detected in group NGC 5846, and compare with optical surveys such Sloan Digital Sky Survey (SDSS; York et al. 2000) as the Sloan Digital Sky Survey (SDSS). Results will be HI, shown in Figure 4. compared with other groups as a part of the Undergraduate ALFALFA Team (UAT) group project. In NGC 5846, 34% of the total members are detected in HI; NGC 5775, 67%; LDCE 1076, NGC 5775 Group Contour and Optical 61%; USGC U648, 50%. ALFALFA (Arecibo Legacy Fast Arecibo Comparisons: L-band Feed Array) AGC 9579 AGC 9576 On-going second generation survey for neutral hydrogen (HI) gas in the local Universe. (Giovanelli SBc? edge-on Type: SAB(rs)d

et al. 2005) NGC 5846 Uses Arecibo telescope, the largest single-dish radio telescope in the world, located in Puerto Rico

ALFALFA Southern limit Figure 1. Arecibo Figure 3. Plot of simplified Telescope AGC 9576/9 combined mass: 1.5x1010 M⊙ groups and member galaxies. NGC 5846 group Figure 4. Plot of group members (black) and HI detections (maroon) in the region. Motivation: Census of galaxies with neutral hydrogen Two uncatalogued objects: Expected to detect ~30,000 objects within 750 million light years Morphology: Critical to studies of galaxy distribution and We examined the optical images of group members via the SDSS in order to evolution independently confirm morphology of each with the accepted catalog values. Union group studying NGC 5846 group of galaxies Spiral galaxies typically have greater amounts of HI, corresponding to star and surroundings formation The NGC 5846 group lacks spiral galaxies as compared to the surrounding groups, and is more populated with ellipticals, which is confirmed by the lower amount of HI detected. Detections of HI in Newly Processed Data: Sb AGC 9601 Sa AGC 9573 Sc AGC 9576 S0 AGC 9742 Previous research mapped a 2.5x8 degree region centered on NGC 5846. (O'Brien et al. 2010) Using Interactive Data Language (IDL) programs, E0 Irr we searched different (dwarf) E3 (dwarf) AGC 252398 AGC 9573/4 combined mass: AGC Figure 2. NGC 5775 AGC 252422 velocities to find sources of 9 ⊙ 253656 E7 (dwarf) group detected 2.0x10 M AGC 252556 HI. SB0 AGC 9575

This summer, we extended this region 2.5° N and 7° W. SBa AGC 9715 SBd AGC 250103 SBb AGC 9574 We found nearly 60 individual galaxies in our velocity range with HI. Figure 6. Hubble diagram of example group members. Among the new finds were five galaxies in our AGC 9574 AGC 9573 velocity range that appeared to be a compact group Type: SB(s)b S? / Sab separate from NGC 5846, the NCG 5775 group. Future Work: Acknowledgments: NGC 5775 Complete source extraction from ALFALFA NSF AST-0724918 : 1525 km/s References: data Professor Koopmann and the Union Compact galaxy group Giovanelli, R., et al., 2005, AJ, 130, 2598 Determine group memberships for galaxies Department of Physics and Astronomy O'Brien, K., Chin, S., Smith, S. M., Koopmann, R.A., ALFALFA Team, 2010, in the region ALFALFA Team Five member galaxies and two uncatalogued BAAS, 42, 460 Compare determined morphologies to HI R. Giovanelli, M. Haynes (Cornell) objects in close proximity York, D.G., Adelman, J., Anderson, J.E., et al. 2000, AJ, 120, 1579 content to show correspondences NASA NY Space Grant