Noch's Summer 2009 Progress page

ALFALFA HI Survey for NGC5846 Group

My work is part of the Undergraduate ALFALFA Team Groups Project. I am analyzing the NGC 5846 group.

Characteristics of NGC 5846

• Studied at x-ray and optical wavelengths (e.g. Haynes & Giovanelli 1991, Mahdavi, Trentham and Tully 2005)
• Relatively isolated
• High percentage of early type galaxies: third highest percentage of early type galaxies after Virgo and Fornax clusters (~ 75%)
• Two subgroups surrounding two main elliptical galaxies, NGC 5846 and NGC 5813
• Distance estimated to be 26 Mpc

Started summer by analyzing AGC catalog in vicinity of the group.

Center listed by NED and selected galaxies within 10 by 10 degrees using plotalfa.

Figure1. NGC5846:10 degrees environment. + = Potential Group-Member Galaxies Violet diamond = RA center and Dec center	Figure 2. Velocity histogram of galaxies within ALFALFA range.
Figure 3. NGC5846 potential group-member galaxies + 800-1400 km/s + 1400-2000 km/s + 2000-2600 km/s	Figure 4. NGC5846 velocity histogram. Open histogram:0-3400 km/s Filled histogram: galaxies within 3 degrees
Figure 5. Distance from Center vs. Velocity.	Figure 6.

Figure 7 Galaxy in 1516+01.

No HI ALFALFA source catalog yet Grids 1452+01 - 1516+01 13 sources detected so far All are in AGC Galaxy in image is AGC 9760

Figure 8.	Circle sizes correspond to galaxy brightness: bigger = brighter. Maroon circles: galaxies with HI.
Figure 9.	About 13%

Figure 10.

Optical counterparts Spiral and irregular Range in luminosity

Figure 11. Dwarf galaxies over plotted agc galaxies.

Figure 12. Zoom in of figure 11.

To do

• Complete source extraction in the 1 degree grids
• Examine the 3 degree grids
• Experiment with defining the center of group, group system velocity and velocity dispersion
• Determine group membership
• Look at galaxies with no HI, are they the early types?

Acknowledgment

• NSF - ALFALFA for summer support
• Professor Rebecca Koopmann
• Katie O'Brien
• Cornell EGG and ALFALFA Team