ALFALFA Mini-Conference Summer'10


As part of the Undergraduate ALFALFA Team Groups Project, we are analyzing HI properties of group NGC 5846 in three main aspects:

    I. Complete 3 degree grid & Contour plots for HI source galaxies
    II. Obtain corrected SDSS photometry
    II. Density Indexing

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: 26 Mpc

Updated AGC (Noch).

Figure 1. Velocities of galaxies within 3 degrees around the center

    Well defined group.

Figure 2. HI source galaxies

  • blue squares : no optical counterpart galaxies
  • about 48% of members detected in three-degree
  • about 23% of members dected in one-degree

Contour plots (Halley)

  • * Contour plot of NGC 5775 Group
  • * 5 member galaxies
      ** AGC 9573, 9574, 9576, 9579, 240693
  • cz value range: 1930-1430 km/s
  • coordinates: RA 14 53 24.9, DEC +03 29 47.5
  • 2 observed objects without optical counterparts
      ** RA 14 51 14.0 DEC +03 36 33.1
      ** RA 14 51 07.3 DEC +02 43 09.3

Figure 3. Contour plots for HI detected galaxies in three-degree

Figure 4 .




Photometry (Ana)

Photometry comparison is important for parameters dependent on radius


Figure 5 .



  • The red squares correspond to galaxies detected in Alfalfa




Figure 6.
  • SFI++: petrosian magnitude vs model magnitude (g)
  • Photometry is not consistent for faint sources and really bright ones

Regions of star formation (Katie)

  • CTIO 0.9m images
  • Approximately 15 galaxies will be studied
  • Optical images displayed in R, which traces the stellar distribution, and Ha, which traces the regions of star formation

Figure 7: Galaxy AGC243026 in R on the left and in Ha on the right

Figure 8: The color image of AGC243026 from SDSS




Figure 9: The spectrum of AGC243026 from SDSS

Acknowledgment

  • NSF - ALFALFA for summer support
  • Professor Koopmann
  • Union College
  • Cornell EGG and ALFALFA Team
  • NASA New York Space Grant