Marc Seigar

Last updated
Marc S. Seigar
Marc Seigar.jpg
Education Imperial College London (B.Sc.)
Liverpool John Moores University (Ph.D.)
AwardsInaugural Hoku Outreach Award, Mauna Kea Observatories (2004)
Scientific career
Institutions University of Toledo
National Science Foundation
University of Minnesota Duluth
University of Arkansas at Little Rock
University of California, Irvine
Joint Astronomy Centre
Ghent University
Thesis Observational Studies of the Structure of Spiral Galaxies  (1998)
Doctoral advisor Philip A. James
Doctoral students Burçin Mutlu-Pakdil
Website https://www.marcseigar.net/

Marc S. Seigar is an astrophysicist, academic and author. He is the Dean of the College of Natural Sciences and Mathematics, and a Professor of Physics and Astronomy at the University of Toledo. [1]

Contents

Seigar has published over 140 articles on topics related to galaxy structure and dynamics, galaxy morphology, and spiral structure. [2] He is the author of 2 books entitled Dark Matter in the Universe and Spiral Structure in Galaxies, and has edited a volume on Structure and Dynamics of Disk Galaxies. [3]

Seigar is a member of several professional societies, including Sigma Xi, [4] the International Astronomical Union, the American Astronomical Society, and the Royal Astronomical Society. He is also an Associate of the Royal College of Science. He serves on the editorial board of the journal “Universe”, and is the member of International Astronomical Union’s Executive Committee on Astronomy for Equity and Inclusion. He has conducted numerous invited talks. [5]

Education

Seigar graduated from Imperial College, London in 1993 with a Bachelor of Science in Physics. He then enrolled at Liverpool John Moores University, and earned his Doctoral degree in Astrophysics in 1998 from the Astrophysics Research Institute. [6] His dissertation “Observational Studies of the Structure of Spiral Galaxies”, was supervised by Philip A. James. [7]

Career

Following his doctoral degree, Seigar held concurrent appointments as a postdoctoral research fellow at the University of Ghent, and as a visiting astronomer at the Space Telescope Science Institute until 2001. He held his next appointment as a staff astronomer for the U.K. Infrared Telescope (UKIRT) at the Joint Astronomy Centre from 2001 until 2004. During this time period, he was also concurrently appointed by the University of Hawaii at Hilo as an adjunct professor of physics and astronomy for a year. From 2004 to 2007, he served as an assistant project scientist at the University of California, Irvine, and as visiting astronomer at the observatories of the Carnegie Institution for Science. In 2007, he held joint appointments as an adjunct professor at the University of Arkansas, Fayetteville, and as assistant professor of physics and astronomy at University of Arkansas at Little Rock, [8] where he worked his way through the academic ranks. In 2014, he joined the University of Minnesota Duluth as a professor of physics and astronomy, and served there until 2021. Currently, he holds appointment as a professor in the Department of Physics and Astronomy at the University of Toledo.

Seigar also held administrative appointments in his career. He was appointed as head of the Department of Physics and Astronomy at the University of Minnesota Duluth from 2014 until 2017, and as associate dean at Swenson College of Science and Engineering from 2017 until 2020. [9] He also held an appointment as a Program Director in the Division of Astronomical Sciences at National Science Foundation for a year. As of 2021, he is the dean of the College of Natural Sciences and Mathematics at the University of Toledo. [10]

Research

Seigar’s research primarily focuses on the structure, morphology and dynamics of galaxies, [11] as well as their dark matter halos [12] and the nature of the dark matter particles. [13]

Astronomical databases

Seigar has been involved in several database projects. The first of these is the H-alpha Galaxy Survey (HaGS). HaGS was focused on the selection and observations of 334 galaxies, and found that a correlation exists between total star formation rate and Hubble type, with the strongest star formation in isolated galaxies occurring in Sc and Sbc types. [14] Seigar was also a member of the 850-μm SCUBA Half-Degree Extragalactic Survey (SHADES) which presented maps, source catalogues and number counts of the largest extragalactic submillimetre survey at that time. This survey found out that a 850-μm survey complete down to 2 mJy would resolve 20–30 per cent of the far-infrared background into point sources. In the SHADES paper published in 2007, the team presented a comparison between redshift distributions of sub-mm galaxy formation and evolution models, as well as described the contribution of these SHADES sources and the general sub-mm galaxy population in terms of the star formation rate density at different epochs.

Supermassive black holes

Seigar has developed several methods to estimate supermassive black hole (SMBH) masses. His research team works extensively to develop SMBH mass function, and to provide direct determinations of SMBH masses for nearby galaxies. In 2014, they provided nuclear supermassive black hole (SMBH) mass function for spiral galaxies in the local universe, established from a volume-limited sample consisting of a statistically complete collection of the brightest spiral galaxies in the southern (δ < 0°) hemisphere. [15] He, along with his team, also demonstrated the relationship between spiral arm pitch angle and the mass of supermassive black holes (BHs) in the context of the nuclei of disk galaxies. [16]

Seigar and his team also studied the spiral arm morphology of a sample of the local spiral galaxies in the Illustris simulation, and showed that SMBH mass is related to the total dark matter mass in galaxies. They explored tight correlations that exist between supermassive black hole masses and large-scale properties of the host galaxy, as well as described how halo properties determine those of a disc galaxy and its supermassive black hole. Since 2021, he has focused his research towards finding the evidences regarding the existence of Intermediate-Mass Black Holes (IMBHs) using X-ray and optical images of galaxies. [17]

Dark matter in galaxies

Seigar provided a cosmologically motivated description of the dark matter halo profile for the low surface brightness galaxy, Malin 1. He further found out that the dark matter halo model of Malin 1 can best be described by a halo profile that has undergone adiabatic contraction. In his paper published in 2014, he investigated the usage of spiral arm pitch angles as a probe of disk galaxy mass profiles, as well as discussed the implications regarding the suggested link between supermassive black hole (SMBH) mass and dark halo concentration. [18] He discussed the implications of the Andromeda Galaxy (M31) in terms of testing several ideas of galaxy formation. His research work shows that the rotation curve of Andromeda Galaxy (M31) can only be produced with a mass model that includes a halo that has contracted adiabatically.

Awards and honors

Bibliography

Books

Selected articles

Related Research Articles

<span class="mw-page-title-main">Galaxy formation and evolution</span>

The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby galaxies. Galaxy formation is hypothesized to occur from structure formation theories, as a result of tiny quantum fluctuations in the aftermath of the Big Bang. The simplest model in general agreement with observed phenomena is the Lambda-CDM model—that is, clustering and merging allows galaxies to accumulate mass, determining both their shape and structure. Hydrodynamics simulation, which simulates both baryons and dark matter, is widely used to study galaxy formation and evolution.

<span class="mw-page-title-main">Triangulum Galaxy</span> Spiral galaxy in the constellation Triangulum

The Triangulum Galaxy is a spiral galaxy 2.73 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC (New General Catalogue) 598. With the D25 isophotal diameter of 18.74 kiloparsecs (61,100 light-years), the Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Andromeda Galaxy and the Milky Way.

<span class="mw-page-title-main">Elliptical galaxy</span> Spherical or ovoid mass of stars

An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the four main classes of galaxy described by Edwin Hubble in his Hubble sequence and 1936 work The Realm of the Nebulae, along with spiral and lenticular galaxies. Elliptical (E) galaxies are, together with lenticular galaxies (S0) with their large-scale disks, and ES galaxies with their intermediate scale disks, a subset of the "early-type" galaxy population.

<span class="mw-page-title-main">Supermassive black hole</span> Largest type of black hole

A supermassive black hole is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (M☉). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space from which nothing can escape, including light. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its center. For example, the Milky Way galaxy has a supermassive black hole at its center, corresponding to the radio source Sagittarius A*. Accretion of interstellar gas onto supermassive black holes is the process responsible for powering active galactic nuclei (AGNs) and quasars.

<span class="mw-page-title-main">Spiral arm</span> Spiral-shaped regions of enhanced brightness within the galactic disc in spiral galaxies

Spiral arms are a defining feature of spiral galaxies. They manifest as spiral-shaped regions of enhanced brightness within the galactic disc. Typically, spiral galaxies exhibit two or more spiral arms. The collective configuration of these arms is referred to as the spiral pattern or spiral structure of the galaxy.

<span class="mw-page-title-main">Galactic bulge</span> Tightly packed group of stars within a larger formation

In astronomy, a galactic bulge is a tightly packed group of stars within a larger star formation. The term almost exclusively refers to the central group of stars found in most spiral galaxies. Bulges were historically thought to be elliptical galaxies that happened to have a disk of stars around them, but high-resolution images using the Hubble Space Telescope have revealed that many bulges lie at the heart of a spiral galaxy. It is now thought that there are at least two types of bulges: bulges that are like ellipticals and bulges that are like spiral galaxies.

<span class="mw-page-title-main">NGC 1300</span> Galaxy in the constellation Eridanus

NGC 1300 is a barred spiral galaxy located about 65 million light-years away in the constellation Eridanus. The galaxy is about 110,000 light-years across. It is a member of the Eridanus Cluster, a cluster of 200 galaxies, in a subgroup of 2-4 galaxies in the cluster known as the NGC 1300 Group. It was discovered by John Herschel in 1835.

<span class="mw-page-title-main">NGC 3593</span> Galaxy in the constellation Leo

NGC 3593 is a lenticular galaxy located in the constellation Leo. It has a morphological classification of SA(s)0/a, which indicates it is a lenticular galaxy of the pure spiral type. Despite this, it has a large amount of hydrogen, both in its molecular and atomic (H) form. It is a starburst galaxy, which means it is forming new stars at a high rate. This is occurring in a band of gas surrounding the central nucleus. There is a single arm, which spirals outward from this ring. It is frequently but not consistently identified as a member of the Leo Triplet group.

In astronomy, the velocity dispersion (σ) is the statistical dispersion of velocities about the mean velocity for a group of astronomical objects, such as an open cluster, globular cluster, galaxy, galaxy cluster, or supercluster. By measuring the radial velocities of the group's members through astronomical spectroscopy, the velocity dispersion of that group can be estimated and used to derive the group's mass from the virial theorem. Radial velocity is found by measuring the Doppler width of spectral lines of a collection of objects; the more radial velocities one measures, the more accurately one knows their dispersion. A central velocity dispersion refers to the σ of the interior regions of an extended object, such as a galaxy or cluster.

<span class="mw-page-title-main">NGC 1964</span> Galaxy in the constellation Lepus

NGC 1964 is a barred spiral galaxy in the constellation Lepus. The galaxy lies 65 million light years away from Earth, which means, given its apparent dimensions, that NGC 1964 is approximately 100,000 light years across. At its center lies a supermassive black hole, with estimated mass 2.5 × 107M☉. The galaxy features two tightly wound inner spiral arms within a disk with high surface brightness and two outer, more open spiral arms that originate near the inner ring. The outer arms feature few small HII regions.

<span class="mw-page-title-main">Burçin Mutlu-Pakdil</span> Turkish astrophysicist

Burçin Mutlu-Pakdil is a Turkish-American astrophysicist, and Assistant Professor at Dartmouth College. She formerly served as a National Science Foundation (NSF) and Kavli Institute for Cosmological Physics (KICP) Postdoctoral Fellow at the University of Chicago. Her research led to a discovery of an extremely rare galaxy with a unique double-ringed elliptical structure, which is now commonly referred to as Burcin's Galaxy. She was also a 2018 TED Fellow, and a 2020 TED Senior Fellow.

<span class="mw-page-title-main">NGC 2280</span> Spiral galaxy in the constellation Canis Major

NGC 2280 is a spiral galaxy located in the constellation Canis Major. It is located at a distance of circa 75 million light years from Earth, which, given its apparent dimensions, means that NGC 2280 is about 135,000 light years across. It was discovered by John Herschel on February 1, 1835.

<span class="mw-page-title-main">NGC 7606</span> Galaxy in the constellation Aquarius

NGC 7606 is a spiral galaxy located in the constellation Aquarius. It is located at a distance of circa 100 million light years from Earth, which, given its apparent dimensions, means that NGC 7606 is about 165,000 light years across. It was discovered by William Herschel on September 28, 1785. The galaxy is included in the Herschel 400 Catalogue. It lies 45 arcminutes northeast from psi2 Aquarii. It can be seen with a 4 inch telescope but its visibility is greatly affected by light pollution.

<span class="mw-page-title-main">NGC 7723</span> Galaxy in the constellation Aquarius

NGC 7723 is a barred spiral galaxy located in the constellation Aquarius. It is located at a distance of circa 90 million light years from Earth, which, given its apparent dimensions, means that NGC 7723 is about 95,000 light years across. It was discovered by William Herschel on November 27, 1785. The galaxy is included in the Herschel 400 Catalogue. It lies 1.5 degrees north-northwest from Omega1 Aquarii. It can be seen with a 4-inch telescope under dark skies.

<span class="mw-page-title-main">NGC 753</span> Galaxy in the constellation Andromeda

NGC 753 is a spiral galaxy located 220 million light-years away in the constellation Andromeda. The galaxy was discovered by astronomer by Heinrich d'Arrest on September 16, 1865 and is a member of Abell 262.

<span class="mw-page-title-main">NGC 3511</span> Galaxy in the constellation Crater

NGC 3511 is an intermediate spiral galaxy located in the constellation Crater. It is located at a distance of circa 45 million light years from Earth, which, given its apparent dimensions, means that NGC 3511 is about 70,000 light years across. It was discovered by William Herschel on December 21, 1786. It lies two degrees west of Beta Crateris.

<span class="mw-page-title-main">NGC 7531</span> Galaxy in the constellation Grus

NGC 7531 is an intermediate spiral galaxy located in the constellation Grus. It is located at a distance of about 70 million light-years from Earth, which, given its apparent dimensions, means that NGC 7531 is about 95,000 light years across. It was discovered by John Herschel on September 2, 1836.

<span class="mw-page-title-main">NGC 2525</span> Galaxy in the constellation Puppis

NGC 2525 is a barred spiral galaxy located in the constellation Puppis. It is located at a distance of about 70 million light years from Earth, which, given its apparent dimensions, means that NGC 2525 is about 60,000 light years across. It was discovered by William Herschel on February 23, 1791.

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References

  1. ↑ "Faculty: Dr. Marc Seigar". www.utoledo.edu. Retrieved 2022-07-18.
  2. ↑ "The link between black holes and spiral arms | Space | EarthSky". earthsky.org. 2009-02-27. Retrieved 2022-07-18.
  3. ↑ "Marc Seigar". scholar.google.com. Retrieved 2022-07-18.
  4. ↑ "Member Directory". www.sigmaxi.org. Retrieved 2022-07-18.
  5. ↑ "International Astronomical Union | IAU". www.iau.org. Retrieved 2022-07-18.
  6. ↑ "Faculty: Dr. Marc Seigar". www.utoledo.edu. Retrieved 2022-07-23.
  7. ↑ "Observational studies of the structure of spiral galaxies. - British Library". explore.bl.uk. Retrieved 2022-07-23.
  8. ↑ "Marc Seigar, Ph.D. Honored by Cambridge Who's Who for Excellence in Astronomy and Cosmology Research and Education". 24-7 Press Release Newswire. Retrieved 2022-07-18.
  9. ↑ "Mentors | Swenson College of Science and Engineering". scse.d.umn.edu. Retrieved 2022-07-18.
  10. ↑ "New Dean Selected to Lead UToledo College of Natural Sciences and Mathematics | UToledo News". 2021-06-01. Retrieved 2022-07-18.
  11. ↑ Jesse Emspak (2017-01-04). "This Double-Ringed Galaxy Is One of the Rarest Types Ever Seen". Space.com. Retrieved 2022-07-18.
  12. ↑ "How to weigh a black hole without getting off the couch". cosmosmagazine.com. 2017-07-24. Retrieved 2022-07-18.
  13. ↑ "Marc Seigar's articles on arXiv". arxiv.org. Retrieved 2022-07-18.
  14. ↑ James, P. A.; Shane, N. S.; Beckman, J. E.; Cardwell, A.; Collins, C. A.; Etherton, J.; de Jong, R. S.; Fathi, K.; Knapen, J. H.; Peletier, R. F.; Percival, S. M. (2004-01-01). "The Hα galaxy survey. I. The galaxy sample, Hα narrow-band observations and star formation parameters for 334 galaxies". Astronomy and Astrophysics. 414: 23–43. arXiv: astro-ph/0311030 . Bibcode:2004A&A...414...23J. doi: 10.1051/0004-6361:20031568 . ISSN   0004-6361. S2CID   1268388.
  15. ↑ Davis, Benjamin L.; Berrier, Joel C.; Johns, Lucas; Shields, Douglas W.; Hartley, Matthew T.; Kennefick, Daniel; Kennefick, Julia; Seigar, Marc S.; Lacy, Claud H. S. (2014-06-20). "The Black Hole Mass Function Derived from Local Spiral Galaxies". The Astrophysical Journal. 789 (2): 124. arXiv: 1405.5876 . Bibcode:2014ApJ...789..124D. doi: 10.1088/0004-637x/789/2/124 . ISSN   0004-637X. S2CID   119302157.
  16. ↑ Seigar, Marc S.; Kennefick, Daniel; Kennefick, Julia; Lacy, Claud H. S. (2008-04-14). "Discovery of a Relationship between Spiral Arm Morphology and Supermassive Black Hole Mass in Disk Galaxies". The Astrophysical Journal. 678 (2): L93–L96. arXiv: 0804.0773 . Bibcode:2008ApJ...678L..93S. doi:10.1086/588727. ISSN   0004-637X. S2CID   2799015.
  17. ↑ Brunner-Huber, Eli W.; Seigar, Marc S. (2021). "Hunting for Intermediate-Mass Black Holes Using X-ray and Optical Images of Galaxies". hdl:11299/223263.{{cite journal}}: Cite journal requires |journal= (help)
  18. ↑ Seigar, Marc S.; Davis, Benjamin L.; Berrier, Joel; Kennefick, Daniel (2014-10-15). "Constraining Dark Matter Halo Profiles and Galaxy Formation Models Using Spiral Arm Morphology. Ii. Dark and Stellar Mass Concentrations for 13 Nearby Face-On Galaxies". The Astrophysical Journal. 795 (1): 90. arXiv: 1409.6667 . Bibcode:2014ApJ...795...90S. doi:10.1088/0004-637x/795/1/90. ISSN   1538-4357. S2CID   119267077.
  19. ↑ "Alumni". cosmology.uci.edu. Retrieved 2022-07-23.
  20. ↑ "Member Directory". www.sigmaxi.org. Retrieved 2022-07-23.
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