NMSUAstronomy

I am currently working with Dr. Anatoly Klypin simulating tidal stripping in dwarf galaxies around Milky Way sized galaxies. The title and truncated abstract for our submitted paper, Arraki et al. 2013, is given below.

Kenza S. Arraki, Anatoly Klypin, Surhud More, Sebastian Trujillo-Gomez
Effects of baryon removal on the structure of dwarf spheroidals
Dwarf spheroidal galaxies (dSphs) are extremely gas poor, dark matter-dominated galaxies, which make them ideal to test the predictions of the Cold Dark Matter (CDM) model. We argue that the removal of a small baryonic component from the central regions of forming dSphs may substantially reduce their central dark matter density. Thus it may play an important role in alleviating one of the problems of the CDM model related with the structure of relatively massive satellite galaxies of the Milky Way. Traditionally, collisionless cosmological N-body simulations are used when confronting theoretical predictions with observations. However, these simulations assume that the baryon fraction is equal to the cosmic mean, an assumption which can be incorrect for dSphs. We find that the combination of (i) the lower baryon fraction in dSphs compared to the cosmic mean and (ii) the concentration of baryons in the inner part of the Milky Way halo can go a long way towards explaining the observed circular velocity profiles of dSphs. We find that the blowing away of baryons by ram pressure, when the dwarfs fall into larger galaxies, lowers the circular velocity profile of the satellite. In the central ~200-500 pc region of the galaxies the dark matter density is expected to decline by a factor of (1 - f_b)^4 ~ 0.5, where f_b is the cosmological fraction of baryons. In addition, the enhanced baryonic mass in the central regions of the parent galaxy generates tidal forces, which are larger than those experienced by subhaloes in traditional N -body simulations. Increased tidal forces substantially alter circular velocity profiles for satellites that come as close as 50 kpc. We show that these two effects are strong enough to bring the observed structure of dSphs into agreement with the predictions of the subhaloes in CDM simulations, regardless of the details of the baryonic processes.

For a short introduction to my previous work please read the text below.

I received my B. S. degree in June 2010 from the University of Washington.

During my undergraduate education, I worked with Dr. Andrew Becker extracting asteroid detections from Sloan Digital Sky Survey (SDSS) observations and reporting them to the Minor Planets Center. We discovered over 700 new objects, and confirmed 13,000 more which had been previously discovered. These data will help to create a more accurate picture of the behavior and orbital patterns of these objects. Additionally, I worked with Dr. Becker on the ESSENCE Supernova Survey, searching for trans-Neptunian Objects.

I also worked at Goddard Space Flight Center with Bruce Woodgate and Carol Grady to derive inclinations for jet-driving T Tauri stars. NASA's MUST program provided me with the internship that began my work on this project.

Since 2008 I have worked with Dr. Daryl Haggard on variability in broad absorption line (BAL) region of quasars. We have observed seventeen systems with the FAST spectrograph on the Fred Lawrence Whipple Observatory 1.5-meter Telescope. We are focused on determining the appropriate time scales on which changes in the BAL spectra can be detected, by observing true variation and modeling variable effects in tandem. This will help to constrain the size of the emitting and absorbing gas cloud near to the super-massive black holes at the cores of these objects. The University of Washington's EIP Presidential Scholarship funded part of this work. I am also using my current NSF GRFP to fund my continued work on this project.

During my graduate studies I have worked with both Dr. Anatoly Klypin in the extragalactic theory group and Dr. Chris Churchill in the quasar absorption line group.

Publications

Effects of baryon removal on the structure of dwarf spheroidal galaxies
Arraki, K. S.; Klypin, A.; More, S.; Trujillo-Gomez, S.

Constraining Variable High Velocity Winds from Broad Absorption Line Quasars with Multi-Epoch Spectroscopy
Haggard, D.; Arraki, K. S.; Green, P. J.; Aldcroft, T.; Anderson, S. F.

PDS 144: The First Confirmed Herbig Ae-Herbig Ae Wide Binary
Hornbeck, J. B.; Grady, C. A.; Perrin, M. D.; Wisniewski, J. P.; Tofflemire, B. M.; Brown, A.; Holtzman, J. A.; Arraki, K.; Hamaguchi, K.; Woodgate, B.; Petre, R.; Daly, B.; Grogin, N. A.; Bonfield, D. G.; Williger, G. M.; Lauroesch, J. T.

The FAST BAL Monitoring Campaign: Multi-epoch Constraints on Quasar Outflows
Arraki, Kenza S.; Haggard, D.; Anderson, S.; Green, P.; Aldcroft, T.

The Disks, Envelopes, Jets and Environment of PDS 144: A Wide Herbig Ae Binary
Hornbeck, J.; Grady, C. A.; Hamaguchi, K.; Williger, G. M.; Perrin, M.; Grogin, N.; Wisniewski, J.; Brown, A.; Woodgate, B.; Petre, R.; Daly, B.; Arraki, K.

Variable High Velocity Winds from Broad Absorption Line Quasars
Kenza S. Arraki, D. Haggard, S. Anderson, P. Green, & T. Aldcroft 2011, BAAS, 43, 2011

Probing Disk Stratification by Combining X-ray and Disk Inclination Data for Taurus-Auriga
Kenza S. Arraki, B. Daly, M. Harding, J. McCleary, A. W. Cox, C. A. Grady, B. E. Woodgate, K. Hamaguchi, J. P. Wisniewski, S. Brakken-Thal, G. Hilton, D. Bonfield, & G. M. Williger 2010, BAAS, 42, 349

Exploring the Outer Solar System with the ESSENCE Supernova Survey
A. C. Becker, K. Arraki, N. A. Kaib, W. M. Wood-Vasey, et al. 2010, ApJ, 682, L53