# Early Interactions with Vera Rubin

Note from Joel E. Tohline:  Whether she knew it or not, Dr. Vera C. Rubin was a significant influence on my early astronomy career. What follows are some highlights of my early professional interactions with her.

## Neighborhood Meeting at Yale University (1979)

Yale Neighborhood Meeting (1979)
For two years, beginning in the summer of 1978, I held a J. Willard Gibbs instructorship in the astronomy department at Yale University. In my first year, I was encouraged — along with another young astronomer, Dr. Carol A. Christian — to organize a so-called Neighborhood Meeting at Yale. The idea was to focus on a topic that would bring together faculty, postdocs and graduate students from universities and research centers that were "within driving distance" of the Yale campus; this, and limiting the gathering to 1½ days (just one overnight stay) would keep travel expenses to a minimum. We accepted the challenge. Given that, at that time, the astrophysics community, worldwide, was making significant progress on a number of issues related to galaxies — both observationally and theoretically — the topic we picked was …
Rotation: The Dynamical Structure of Galaxies
(A Neighborhood Meeting at Yale University)
Dates: 23 - 24 March 1979

Dr. Vera Rubin agreed to be our opening speaker. It was an opportunity for the (> 90) attendees to hear and see — first hand from the expert — how significant the evidence was for flat rotation curves. Five speakers followed: Dr. Jeremiah Ostriker (Princeton), Dr. Alar Toomre (MIT), Dr. Kevin Prendergast (Columbia University), Dr. Paul Schechter (Harvard-Smithsonian CfA), and Dr. Richard Miller (Chicago).

## Tohline Visits CIW:DTM (1980)

In early February, 1980, I visited the Carnegie Institution of Washington's Department of Terrestrial Magnetism (CIW:DTM) in Washington, DC to meet and interact with Vera Rubin and her research group. During that visit, I had the opportunity to present an informal talk in which I pitched the idea that flat rotation curves in galaxies might be explained by modifying Newton's law of gravity at large distances. This is the idea that I first presented in a formal manner at the IAU Symposium No. 100 in a paper titled, Stabilizing a Cold Disk with a 1/r Force Law.

## IAU Symposium No. 100 (1982)

An astronomical symposium sanctioned by the International Astronomical Union (IAU) titled, Internal Kinematics and Dynamics of Galaxies, was held in Besancon, France, August 9 - 13, 1982. This is the professional conference at which I presented a short "poster paper" titled, "Stabilizing a Cold Disk with a 1/r Force Law.". It appears as a two-page article that begins on p. 105 of the published symposium proceedings.

Dr. Rubin was (again!) the lead-off speaker for this five-day symposium; accordingly, the paper that she prepared for the symposium — titled, Systematics of HII Rotation Curves — appears as the first article (pp. 3 - 8) in the proceedings. Two pages of text (pp. 9 - 10) that immediately following her article record six questions that were asked of Dr. Rubin at the end of her presentation, along with her six responses. The sixth question was from me; here is the published record:

 TOHLINE:   I would like to emphasize at the opening of this symposium that the often quoted ratio M/L is in fact the ratio V2r/L of the directly measurable quantities V, r and L. This ratio V2r/L can only be interpreted as an indicator of mass to light ratio if we assume that Newton's law of gravitational attraction is correct on the scale of galaxies. Since Keplerian behavior is essentially never seen in extra-galactic systems, I might be so bold as to suggest that the validity of Newton's law should now be seriously questioned. I hope that observers who have definitive evidence that Keplerian behavior has been observed in any system will emphasize that evidence at this meeting. RUBIN:   While we have observed that most Sa, Sb and Sc, galaxies have flat or slightly rising rotation curves, a few have slightly falling curves. However, I know of no isolated galaxy with rotation velocities decreasing as rapidly as $V \propto r^{-1 / 2}$. The point you raise is worth keeping in mind although I believe most of us would rather alter Newtonian gravitational theory only as a last resort.

## Rubin's Scientific American Article (1983)

Draft of James E. Felten's (1984) paper
Vera Rubin published a detailed description of the observational evidence for Dark Matter in Spiral Galaxies in the June, 1983 issue of Scientific American (pp. 96 - 108). An excerpt from near the bottom of p. 102 of that article reads,
 "Perhaps the most radical idea for explaining the observed high rotational velocities is one advanced independently by Joel E. Tohline of Louisiana State University and M. Milgrom and J. Bekenstein of the Weizmann Institute of Science. They have proposed that at great distances the Newtonian theory of gravitation must be modified, thereby allowing rotational velocities in galaxies to remain high at such distances from the galactic center even in the absence of unseen mass." -- Vera C. Rubin

This nod of recognition from Dr. Rubin broadened my visibility — both professionally and among the public — more than any other single citation. About half a year later, Dr. James E. Felten — at the time, a research scientist at the NASA Goddard Space Flight Center in Maryland — was discussing with Dr. Rubin the published work of Milgrom & Bekenstein and she told him that Joel Tohline "worked on 'Milgrom' ideas before Milgrom!" (See Felten's hand-written comment inside the red oval of the image shown here, on the right.). I presume that Dr. Rubin was recalling the discussion that I had had with her group in early 1980. Dr. Felten then contacted me and we exchanged a few letters on the subject. Dr. Felten's critique of the Milgrom-Bekenstein work was published in The Astrophysical Journal (1984, 286, pp. 3-6); page 5 of this article includes a Note added in manuscript 1984 June 6 acknowledging these discussions.