Pitch Angles of Clustered Spiral Galaxies in the Chandra Deep Field South. Jazmin Berlanga Medina 1 , Benjamin Davis 2 , Daniel Kennefick 1,2 1 University of Arkansas-Fayetteville, 2 Arkansas Center for Space & Planetary Sciences.
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Pitch Angles of Clustered Spiral Galaxies in the Chandra Deep Field South
JazminBerlanga Medina1, Benjamin Davis2,
1 University of Arkansas-Fayetteville, 2Arkansas Center for Space & Planetary Sciences
We have examined a set of 125 spiral galaxies lying in the Chandra Deep Field South for which we have redshifts & pitch angles from previous work. Upon cross-referencing this set with the larger & comprehensive COMBO-17 survey, we found a cluster that is confirmed by recent literature. When comparing the pitch angle of galaxies in & out of clustered regions, there seems to be little to no difference, suggesting no environmental effect of clusters on pitch angle.
1) We found a cluster at z~1.04. Seems to be the same one found by Trevese et al. (z~0.96, 2009)4
Chandra Deep Field South
What is pitch angle?
Figs. 1 & 2, Location vs. Redshift, Above: The red dots are galaxies with >1000 galaxies in their cylinders, collectively they make up a cluster and lie at a higher z. The blue dots are mostly outside the clustered region, with the higher z galaxies on the fringe of the cluster.
2) No correlation between pitch angle and clustering. Appears so far that clustering has no environmental effect on pitch angle.
3-D in a Cylinder:
Distinguishing false neighbors from real ones3
Fig. 3, Neighbor Count vs. Pitch angle, Left: The red line represents the relationship between number of neighbors and pitch angle—the slope is very nearly zero.
BUT…Not yet understood how environmental factors (i.e., galaxy harassment, dark matter concentration) affect spiral arm structure—including pitch angle. Need to know that pitch angle estimate of black hole mass is reliable across different environments.
Tbl. 1, Bins, Right: When grouped into statistically- proportional groups, the pitch angles in clustered & non were nearly the same.
So why clusters?
Programming: Wrote Fortran program to find number of actual neighbors in cylinder
1) Determine more about cluster. Need exact dimensions, map of galaxy density (galaxies/volume), which of COMBO-17 galaxies not in our set are part of cluster.
2) Careful comparison between Trevese et al.’s cluster & ours: Data, technique, etc.
3) Part of our original pitch angle vs. black hole mass sample of galaxies is in the Hubble Deep Field North. Will repeat procedure with this set.
Looked at our set of galaxies one at a time, calculated distance to every object in COMBO-17
Counted number of objects within 10 Mpc radius
Threw out false neighbors not within z range
Literature: What is already known about spiral galaxies in clusters? Are there known clusters in
Found several sources on galaxy morphology in clusters
All agree: Lenticular to spiral galaxy ratio changes in favor of lenticular over time (higher to lower redshift)
Speculations: Could spirals evolve with tighter & tighter arms towards lenticulars? Could cluster environment weed out/disturb spirals all-together over time?
References:  Seigar M. S., et al. (2008) ApJ., 678, 93-96.  Wolf C. et al. (2004) Astro. and Astrophys., 421, 913-936.  Berrier J. (2009) Private Communication.  Trevese D. et al. (2009) AIP Conf. Proc., 1126, 125-127.
Acknowledgements: I’d like to thank my mentor, Dr. Dan Kennefick, & grad students Doug Shields & Ben Davis, for enlightening many a concept, the Honors College at U of A for the research grant, and my physics advisor Dr. Lin Oliver for all the encouragement.