Dr. Nikole M. Nielsen

Postdoctoral Research Associate Swinburne University of Technology

Research

The focus of my research is to understand how galaxies form and evolve by examining the properties and motions of gas in the circumgalactic medium (CGM), a massive and diffuse reservoir of gas surrounding galaxies.

I study the baryon cycle, or the flow of gas into and out of galaxies, as cosmological simulations have shown it is vital in regulating galaxy evolution and building up the CGM. Quasar absorption lines due to light from a background quasar piercing the CGM of a foreground galaxy are a powerful tool to obtain detailed gas properties such as the ionization balance, chemical content, density, temperature, and kinematics. By comparing the absorption to the host galaxy properties (color, redshift, orientation, etc.), I determine whether the gas being probed is likely accreting from the intergalactic medium or the CGM (recycled accretion), outflowing from star formation in the galaxy, or being tidally stripped from merging satellite galaxies. This allows me to constrain the role that the baryon cycle plays in galaxy evolution and to test predictions from the simulations.

My main source of data is the MgII Absorber–Galaxy Catalog, or MAGIICAT, and contains both MgII doublet absorption and galaxy data for 182 absorber–galaxy pairs. We have a series of papers which describe MAGIICAT and look at basic properties of the CGM as a function of galaxy properties such as color, redshift, impact parameter, mass, and orientation. Our most recent work has used a subset of MAGIICAT data with high-resolution spectra to examine how gas kinematics depend on galaxy properties. Interestingly we found that absorption is found most prominently near the projected major and minor axes of galaxies and that both the azimuthal angle and galaxy inclination play a big part in determining the velocity structure of the absorbers in quasar spectra.

I am currently involved in expanding the catalog of absorber–galaxy pairs to absorption lines tracing higher temperature gas and therefore different baryon cycle processes. I am also interested in examining the CGM in hydrodynamical simulations to obtain a more physical picture of the processes occurring and how they influence our observations.

Curriculum vitae

Education

New Mexico State University, Las Cruces, NM, USA
 Ph.D., Astronomy
  Dissertation: Tracing Galaxy Evolution Through Spatial and
  Kinematic Probes of the MgII Circumgalactic Medium
  Advisor: Christopher W. Churchill		 May 2015
 M.S., Astronomy December 2013
Michigan State University, East Lansing, MI, USA
 B.S., Astrophysics
  Advisor: Timothy C. Beers
  Honors College 		May 2009

Professional Development


Postdoctoral Research Associate 2015–Present
 Centre for Astrophysics and Supercomputing
 Swinburne University of Technology, Melbourne, VIC, Australia
 — Colloquium Organizer (Aug 2016-Present)
Graduate Research Assistant 2009–2015
 Department of Astronomy
 New Mexico State University, Las Cruces, NM, USA
Graduate Teaching Assistant 2009–2011
 Department of Astronomy
 New Mexico State University, Las Cruces, NM, USA
 — Head Teaching Assistant (Fall 2011)
 — Head Observatory TA (Fall 2010 and Fall 2011)
Undergraduate Research Assistant 2008–2009
 Department of Physics and Astronomy
 Michigan State University, East Lansing, MI, USA
Undergraduate Teaching Assistant 2007–2009
 Department of Physics and Astronomy
 Michigan State University, East Lansing, MI, USA

Grants and Awards


IAU Travel Grant to IAUS321 2016
NMSU Alumni Association Outstanding Graduate Award for
 the Graduate School, Ph.D.		 2015
NMSU Graduate Research Enhancement Grant, Office of the
 Vice President for Research		 2012–2015
NMSU College of Arts and Sciences Graduate Travel Award 2014
NASA STScI Hubble Space Telescope Cycle 21 Large Program, co-I 2013–2014
NMSU Astronomy Zia Award for Outstanding Research 2013
NSF East Asia and Pacific Summer Institutes Fellowship at
 Swinburne University of Technology in Melbourne, Australia		 2012
New Mexico Space Grant Graduate Research Fellowship 2010, 2012

Observing


Awarded Time as PI: Keck-II
Awarded Time as Co-I: HST, Keck-II, APO 3.5m
Observed on: Keck-II, APO 3.5m

Supervising Experience


Associate Supervisor of Swinburne PhD student Stephanie Pointon 2016–Present
Mentor to NMSU undergraduate student Amber Medina 2013–2015
Mentor to NMSU undergraduate student Mercedes Maldonado 2013–2015

Professional Organizations


Scientific referee for the Astrophysical Journal 2014–Present
American Astronomical Society 2012–Present
NMSU Astronomy Department Graduate Awards Committee
 Graduate Student Representative		 2014–2015
NMSU Astronomy Graduate Student Organization 2009–2015
 President, Faculty–Student Liaison 2011–2012
 Vice President, Department Outreach Coordinator 2010–2011
Sigma Pi Sigma Physics Honor Society 2009–Present
Society of Physics Students 2005–2009
 President 2008–2009
 Secretary 2007–2008

References


Professor Chris Churchill
New Mexico State University
cwc (at) nmsu.edu 		Dr Glenn Kacprzak
Swinburne University of Technology
gkacprzak (at) swin.edu.au
Professor Michael Murphy
Swinburne University of Technology
mmurphy (at) swin.edu.au

Publications — ADS Compilation

Refereed Publications


15. The Impact of the Group Environment on the OVI Circumgalactic Medium
Pointon, S. K., Nielsen, N. M., Kacprzak, G. G., Muzahid, S., Churchill, C. W., & Charlton, J. C. 2017, ApJ, 844, 23
14. The Highly Ionized Circumgalactic Medium is Kinematically Uniform Around Galaxies
Nielsen, N. M., Kacprzak, G. G., Muzahid, S., Churchill, C. W., Murphy, M. T., & Charlton, J. C. 2017, ApJ, 834, 148
13. MAGIICAT IV. Kinematics of the Circumgalactic Medium and Evidence for Quiescent Evolution Around Red Galaxies
Nielsen, N. M., Churchill, C. W., Kacprzak, G. G., Murphy, M. T., & Evans, J. L. 2016, ApJ, 818, 171
12. The Azimuthal Dependence of Outflows and Accretion Detected Using OVI Absorption
Kacprzak, G. G., Muzahid, S., Churchill, C. W., Nielsen, N. M., & Charlton, J. C. 2015, ApJ, 815, 22
11. MAGIICAT V. Orientation of Outflows and Accretion Determine the Kinematics and Column Densities of the Circumgalactic Medium
Nielsen, N. M., Churchill, C. W., Kacprzak, G. G., Murphy, M. T., & Evans, J. L. 2015, ApJ, 812, 83
10. An Extreme Metallicity, Large-Scale Outflow from a Star-Forming Galaxy at z~0.4
Muzahid, S., Kacprzak, G. G., Churchill, C. W., Charlton, J. C., Nielsen, N. M., Mathes, N. L., & Trujillo-Gomez, S. 2015, ApJ, 811, 132
9. Halo Mass Dependence of HI and OVI Absorption: Evidence for Differential Kinematics
Mathes, N. L., Churchill, C. W., Kacprzak, G. G., Nielsen, N. M., Trujillo-Gomez, S., Charlton, J., & Muzahid, S. 2014, ApJ, 792, 128
8. MAGIICAT III. Interpreting Self-Similarity of the Circumgalactic Medium with Virial Mass Using MgII Absorption
Churchill, C. W., Trujillo-Gomez, S., Nielsen, N. M., & Kacprzak, G. G. 2013, ApJ, 779, 87
7. The Smooth MgII Gas Distribution Through the Interstellar/Extra-planar/Halo Interface
Kacprzak, G. G., Cooke, J., Churchill, C. W., Ryan-Weber, E. V., & Nielsen, N. M. 2013, ApJ, 777, L11
6. MAGIICAT I. The MgII Absorber-Galaxy Catalog
Nielsen, N. M., Churchill, C. W., Kacprzak, G. G., & Murphy, M. T. 2013, ApJ, 776, 114
5. MAGIICAT II. General Characteristics of the MgII Absorbing Circumgalactic Medium
Nielsen, N. M., Churchill, C. W., & Kacprzak, G. G. 2013, ApJ, 776, 115
4. The Redshift Distribution of Intervening Weak MgII Quasar Absorbers and a Curious Dependence on Quasar Luminosity
Evans, J. L., Churchill, C. W., Murphy, M. T., Nielsen, N. M., & Klimek, E. S. 2013, ApJ, 768, 3
3. The Self-Similarity of the Circumgalactic Medium with Galaxy Virial Mass: Implications for Cold-Mode Accretion
Churchill, C. W., Nielsen, N. M., Kacprzak, G. G., & Trujillo-Gomez, S. 2013, ApJ, 763, L42
2. Tracing Outflows and Accretion: A Bimodal Azimuthal Dependence of MgII Absorption
Kacprzak, G. G., Churchill, C. W., & Nielsen, N. M. 2012, ApJ, 760, L7
1. Quenched Accretion of a Large Scale Metal-Poor Filament due to Virial Shocking in the Halo of a Massive z=0.7 Galaxy
Churchill, C. W., Kacprzak, G. G., Steidel, C. C., Spitler, L. R., Holtzman, J. A., Nielsen, N. M., & Trujillo-Gomez, S. 2012, ApJ, 760, 68

Conference Proceedings


2. Gas Kinematics in the Multiphase Circumgalactic Medium
Nielsen, N. M., Kacprzak, G. G., Churchill, C. W., Murphy, M. T., Muzahid, S., Charlton, J. C., & Evans, J. L. 2017, in IAU Symposium 321, Formation and Evolution of Galaxy Outskirts, ed. A. Gil de Paz, J. H. Knapen, & J. C. Lee, 345
1. HST Observations Reveal the Curious Geometry of Circumgalactic Gas
Kacprzak, G. G., Muzahid, S., Churchill, C. W., Nielsen, N. M., & Charlton, J. C. 2017, in IAU Symposium 321, Formation and Evolution of Galaxy Outskirts, ed. A. Gil de Paz, J. H. Knapen, & J. C. Lee, 342

Conferences and Colloquia

Conferences


The Circle of Life: Connecting the Intergalactic, Circumgalactic, and Interstellar Media in Kruger Park, South Africa August 2017 Talk
What Matter(s) Around Galaxies in Durham, UK June 2017 Talk
ITSO Science Symposium 2017 in Canberra, Australia May 2017 Talk
Crossing the Rubicon in Santarcangelo di Romagna, Italy Sep 2016 Talk
IAUS 321 Formation and Evolution of Galaxy Outskirts in Toledo, Spain Mar 2016 Talk
225th American Astronomical Society Meeting in Seattle, WA Jan 2015 Talk
Santa Cruz Galaxy Workshop in Santa Cruz, CA Aug 2014 Talk
Intergalactic Matters in Heidelberg, Germany Jun 2014 Talk
The Near-Field Deep-Field Connection in Irvine, CA Feb 2014 Poster
The Physical Link Between Galaxies and their Halos in Garching, Germany Jun 2013 Poster
Leiden Summer CGM–Galaxy Interface Workshop in Leiden, Netherlands Jun 2013 Talk
The 28th New Mexico Symposium in Socorro, NM Nov 2012 Talk
STScI May Symposium: Gas Flows in Galaxies in Baltimore, MD May 2012 Poster
219th American Astronomical Society Meeting in Austin, TX Jan 2012 Poster

Colloquia


Swinburne CAASTRO-3D Lunch Talk June 2017 Invited Talk
University of Melbourne Astrophysics Seminar May 2017 Invited Talk
NMSU Astronomy Department Colloquium Mar 2015 Talk
NMSU Graduate Research and Arts Symposium Mar 2015 Poster
NMSU Astronomy Department Pizza Lunch Sep 2014 Talk
NMSU Graduate Research and Arts Symposium Mar 2014 Poster
NMSU Astronomy Department Colloquium May 2013 Talk
NMSU Astronomy Department Pizza Lunch Oct 2012 Talk
NMSU Graduate Research and Arts Symposium Mar 2012 Poster