Name, Faculty Rank, Department:
Dr. Patrick R. Durrell, Associate Professor, Department of Physics & Astronomy
Email: prdurrell@ysu.edu
Web: web.ysu.edu/stem/prdurrell
Title of Sabbatical/FIL Project:
Intergalactic Globular Clusters
Abstract/Overview of Project:
The goals of my FIL in 2013-2014 was to (a) continue my work on searching for, and
quantifying the presence of, the globular clusters in the Virgo Cluster (as part of the Next
Generation Virgo Cluster Survey: NGVS), with the goal of publishing this research, and
(b) to obtain data and begin the analysis (with student help) on a study of the diffuse
intracluster light in the Leo Group of galaxies. Both projects would involve analysis of
deep optical images of both galactic environments.
Sabbatical/FIL Results:
Overview of the NGVS:
I am a co-investigator of a large team of astronomers as part of a massive research
program called the Next Generation Virgo Cluster Survey (NGVS). The primary science
goals of the NGVS are to, for the first time, obtain deep images of the Virgo Cluster
(covering over 100 square degrees of the sky) in order to study the giant galaxies, the
thousands of dwarf galaxies, and the tens of thousands of star clusters expected in this
cluster. Deep images in 5 optical/near-infrared filters, as well as related follow-up
spectroscopy, represents the single largest study of this important galaxy cluster.
The entire NGVS project is led by Dr. Laura Ferrarese at the Herzberg Institute for
Astrophysics, located in Victoria, BC, Canada. The program is built around telescope
observations that were obtained over a 5 year period (Spring 2009 through Spring 2013),
with follow-up observations still underway. As of August 2014, five refereed
publications have been published with NGVS data, with potentially over 40 (!) research
papers planned over the next few years. I am playing a key role in the study of the
globular clusters and the diffuse light in the Virgo Cluster, and the first paper (which I
devoted much of my FIL time to) from these efforts is about to be published. More
details follow.
My primary role in the NGVS project is to lead the study of the thousands of globular
star clusters that are expected to lie between the primary galaxies within the Virgo
Cluster, through measurements of the brightness and colors of object found on the
extremely deep NGVS images. I am also taking part in other subprojects within
the NGVS, including studies of the faint dwarf galaxies that are yet to be discovered in
the data, and input into the detailed photometric analysis of this huge dataset. I am a coauthor on 4 of the 5 papers already published (up to September 2014) using NGVS data,
and I am expected to play a similar role in many upcoming papers (including 2 papers
that have either been submitted for publication, or are weeks away from being
submitted.)
FIL Results: Projects + Peer-Reviewed Publications
The majority of my time on my FIL was taken at the Department of Physics and
Astronomy here at YSU, where I focused almost all of my efforts on the Virgo-NGVS
globular cluster project. However, I also spent a week (in Oct. 2013) visiting the
University of Western Ontario to collaborate with Dr. Sarah Gallagher and Tyler
Desjardins on another research project that I am involved with -- a deep imaging study of
Hickson Compact Group 16. This project is related to the Leo Triplet project that I was
intending to work on during my FIL (where the final data has not yet been acquired).
Research Project 1: The Spatial Distribution of Virgo’s Globular Clusters
Much of my time for the FIL was spent working up the final analyses on the distribution
of globular clusters throughout the entire Virgo Cluster. This work was the culmination
of research initially started in 2011, where I decided to use NGVS data based on only the
2 filters (g' and i') for which the entire Virgo Cluster data had been acquired. (plans to
further these analyses using other filters is ongoing as of Sept. 2014).
As globular
clusters in Virgo will look (on the CCD images) similar to distant background galaxies
and foreground stars in the Milky Way, I used g'-i’ colors to remove some of these
'contaminants', and extensive modeled the background of the remaining contamination in
order to create the final contour map of Virgo's globular clusters, shown in Figure 1.
Fig. 1 Contour map showing the
distribution of globular star clusters
in the Virgo Cluster of galaxies.
The red points denote the locations
of known bright galaxies in the
cluster, while the small black points
show the locations of fainter
galaxies. The globular clusters are
distributed around the most
luminous galaxies in the cluster,
particularly the giant galaxies M87
(top center) and M49 (below center),
which center the most massive sub
clumps in the cluster.
The large research paper based on all of this work was submitted to the Astrophysical
Journal in Spring 2014, and was accepted for publication in August 2014. The paper is
tentatively scheduled to appear in a November 2014 issue of the Astrophysical Journal.
(Note added 1/2015 – paper now published))
Durrell, P.R., Côté, P., Peng, E.W., Blakeslee, J.P., Ferrarese, L., Mihos, J.C., Puzia,
T.H., Lançon, A., Lui, C., Zhang, H., Cuillandre, J.-C., McConnachie, A., Jordan, A.,
Accetta, K., Boissier, S., Boselli, A., Courteau, S., Duc, P.-A., Emsellem, E., Gwyn, S.,
Mei, S., and Taylor, M.E. 2014, The Next Generation Virgo Cluster Survey. VIII. The
Spatial Distribution of Globular Clusters in the Virgo Cluster, the Astrophysical Journal,
in press (Nov. 2014)
(Note added 2/2015: link to published paper
http://iopscience.iop.org/0004-637X/794/2/103/
In addition to this paper, I also contributed to another paper in the NGVS project based
on a study of the globular clusters specifically located around the galaxy M87; this paper
was submitted in Fall 2013, and was published this past spring:
Zhu, L., Long, R. J., Mao, S., Peng, E. W., Liu, C., Caldwell, N., Li, B., Blakeslee, J.P.,
Côté, P., Cuillandre, J.-C., Durrell, P.R., Emsellem, E., Ferrarese, L., Gwyn, S., Jordan,
A., Lançon, A.. Mei, S., Muñoz, R.P., and Puzia, T., 2014 The Next Generation Virgo
Cluster Survey. V. Modeling the Dynamics of M87 with the Made-to-measure Method,
the Astrophysical Journal, 792, 59
(Note added 2/2015: link to published paper
http://iopscience.iop.org/0004-637X/792/1/59/
Future Project 1: Searching for Intragroup Light in the Leo Triplet
One planned project was to apply for telescope time on the Canada-France-Hawaii
Telescope to obtain deep images of the nearby Leo Triplet of galaxies in order to search
for any diffuse light due to the presence of stars between the galaxies in this group. In
2012 data in one filter (i') was taken, but the science goals of the project required data in
3 filters; I applied to obtain the remaining data in 2012 and 2013, and was unable to
obtain data in 2012, and the proposal was not accepted in 2013. While I have resubmitted the proposal to complete the program in Sept. 2014, no work on this particular
project was carried out during the FIL period. It is hoped that the current proposal will
be successful, and with data acquisition in Spring 2015, I hope to have YSU
undergraduates working on this dataset shortly thereafter.
(Note added 2/2015 – proposal was not accepted, thus no new data acquired. Students
are, however, working on data taken as part of other related projects I am involved with)
Presentations:
Over the course of the FIL period, I was invited to present my research (talk title:
Searching for Virgo's Intracluster Globular Clusters) at colloquia at Bucknell University
and at the University of Western Ontario in Oct. 2013. I also presented a public talk on
the Hubble Space Telescope at the Boardman Public Library in Oct. 2013.
Undergraduate Research:
Although I have had 3 YSU undergraduates work with me over the past few years on
projects using NGVS data, none were working for me during my FIL period. However,
one of the students (Katharine Accetta) had been involved in some earlier analyses of the
globular cluster research, and she is a co-author on the paper that is about to be published.
No students were involved in the Leo Triplet study simply due to the lack of data for
them to work on.
FIL Evaluation:
The primary goal of the FIL was to complete the research towards the first paper from the
NGVS on the distribution of globular clusters, with me as the primary author (and YSU
undergraduate Katharine Accetta as a co-author). This was completed, and I am now
focusing my efforts on many of the future papers related to data from the NGVS.
Note: this report was originally submitted September 2014, but has been re-submitted
Feb. 2015 with new template.