Astrophysics (Ay)

The primary aim of the graduate astrophysics program at Caltech is to prepare students for creative and productive careers in astrophysical research and a variety of other challenging vocations. The astrophysics program emphasizes independent research by graduate students, who are free to pursue study in virtually any area of astrophysics. The opportunity exists to take advantage of the many observational facilities owned and operated by Caltech.

Incoming students should have a strong background in physics. Although preparation in astronomy is helpful, this is not required for admission to the graduate program. In addition to demonstrating academic readiness, applicants should provide evidence of research readiness.

While the option does not offer a master’s degree program in itself, students who fulfill the general Institute requirements for such a degree, and the specific option requirements (see below), can receive a master’s degree. This may be either en route to a final Ph.D. degree if admitted to candidacy, or as a terminal degree if the Ph.D. requirements are not met.

The choice of astronomy and other science elective courses must be approved by the option representative. At least 54 units of the 135 units must be selected from Ay 121–127, with at least 36 units earned with a grade of B- or better. The courses Ph 106, Ph 125, and Ph 129 may be required of those students whose previous training in some of these subjects proves to be insufficient. At least 27 units of advanced courses in fields other than astronomy are required.

The student’s proposed overall program of study must be approved by the option representative during the first year.

The following are required of all students for candidacy: Ay 121, Ay 123, Ay 124, Ay 125, Ay 126, and Ay 127. The student should take these courses in the first year. Students must also take at least one term of Ay 122 unless exempted. Also required are research and reading projects. Credit for this work will be given under Ay 142 and Ay 143. The above courses must be passed with a grade of B– or better.

The first two years of graduate study should include at least four courses (36 units) of additional electives relevant to astrophysics, with six courses (54 units) required of theory students. The electives requirement may be reduced for students who need to take Ph 106, Ph 125 or Ph 129 in order to make up for gaps in preparation at the undergraduate level.

Suggested elective courses include, but are not limited to: Ph 101, Ph 105, Ph/Aph 118 a, Ph 127 b, Ph 135, Ph 136 ab, Ph 236 a, Ph 237. For theory students, Ph 136 a and Ph 136 b are required with Ph 136 c and Ph 101 highly recommended, and in addition to Ph, electives in applied mathematics should be considered. For students in observation and experiment, Ph 136 a and Ph 136 b are strongly recommended, and in any case at least one of the four advanced course electives must be in Ph, while the complement may be from other options such as electrical engineering, applied mechanics, computer science, planetary science (geophysics or geochemistry). Seminar courses and research practicum courses do not count as satisfying the requirement for pedagogical elective coursework; however, students are encouraged to take these types of courses during second year. No more than 18 of the elective units may be taken P/F; all others must be passed with a grade of C or better. In the third year and above, students are welcome to enroll in additional advanced astronomy and physics courses.

Each term, the student must be registered for at least 36 academic units, with additional electives such as from PA/PE/HSS allowed on top of the 36. An ability to explain concepts and to verbally present one’s work is vital to a successful career in research and/or teaching. To this end, all graduate students in Astrophysics are required to serve as teaching assistants during their second year, and to make oral presentations as part of the course Ay 141, which must be taken every term during the academic year by all students, beginning in their second year and continuing through graduation.

Graduate students for whom English is a second language may be required to demonstrate fluency in oral and written English at the time of their candidacy exam. The examining committee will arrange for an evaluation if this is deemed necessary.

To be recommended for candidacy for the Ph.D. degree in astrophysics, a student must, in addition to meeting the general Institute requirements:

• pass satisfactorily, or by special examination, the required astrophysics courses (see above);
• pass a general oral qualifying examination (see below);
• complete the physics-based electives course requirement (see above);
• satisfy a teaching requirement (generally two-three terms as a graduate teaching assistant);
• fulfill the language requirement if applicable (see above);
• complete satisfactorily 36 units of research (Ay 142) or reading (Ay143);
• be accepted for thesis research by a member of the faculty.
• pass a thesis candidacy examination (see below).

In fall of their second year, all students are required to take a general oral qualifying examination. Students will be examined on the substance and status of, as well as their performance on, a research project, which should be started not later than the summer following the first year. They will further be examined on their broad understanding of current topics in, and fundamentals of, astrophysics. Both of these aspects of the examination are intended to evaluate the candidate’s aptitude for a research career in astrophysics. In addition, at the discretion of the executive officer, students who have not done well in one, or at most two, areas covered in the Ay 12x course series during their first year will be retested in these areas during the examination. Students must pass all of the aspects of this examination, as judged by the faculty committee conducting it, in order to continue in the Ph.D. program.

Students who do not meet the minimum grade requirements in the Ay 121–127 series, or who do not pass the general candidacy examination described above, will not be able to continue in the Ph.D. program. They may receive a terminal master’s degree, provided that they fulfill the requirements for it (see above).

By the summer of their first year, students should be spending most of their time on research. During their first two years, students are free to work with any faculty they wish, on one or more projects. However, by the summer of their second year at the latest, they should have defined a thesis project and been accepted by a faculty research adviser for that project (in cases where the thesis involves multiple projects, a second faculty adviser may supervise part of the research, but one must be selected as primary adviser). An oral candidacy exam dealing with the student’s proposed thesis research should be completed before the end of the third year. The date and time of the exam are the responsibility of the student to arrange. The candidacy committee is approved by the option representative in consultation with the student’s adviser and informed by a list of suggested members provided by the student. This committee becomes the student’s Thesis Advisory Committee (TAC) and will stand until the final oral thesis defense, and be charged with ensuring that satisfactory progress toward the Ph.D. is being made.

If the candidate does not pass the oral candidacy exam, then the candidacy committee may at its discretion offer the candidate a second oral examination. This examination must be successfully completed by the end of the third term of the third year.

After the oral candidacy exam, the adviser and the student together have primary responsibility for the student’s progress and career development. To ensure that these remain on course, both student and adviser must submit annual progress reports to a representative of the astrophysics program (the option representative, the executive officer, or in the case of a conflict of interest, to the division chair). Furthermore, the student should meet for a “check-in” with the thesis advisory committee members at least once per year. If at any stage the student or the adviser feels that there are serious problems developing, they may consult in confidence with the astrophysics option representative, the executive officer, or the division chair. They may also request a meeting of the committee or seek the advice or help of other faculty members. Students may also consult at any time with the PMA director of student programming or seek confidential advice and help from the Student Wellness Services.

A final draft of the thesis must be submitted to the registrar at least six weeks before the commencement at which the degree is to be conferred. At least two weeks after submission of the thesis, the student will be examined orally on the scope of the thesis and its relation to current research in astrophysics. The examination will be conducted by a committee selected in the same way as the candidacy committee, and is nominally the thesis advisory committee. The oral thesis defense should occur before the end of the fifth year.

Year 1: Ay 121, Ay 123–127; at least two advanced physics courses; reading and independent study. Begin research.

Year 2: Early fall—general oral qualifying examination. Fulfill teaching requirement. Complete 36 units of physics (54 for theorists); a term of Ay 122 if applicable; optional advanced astronomy courses. Ay 141 each term. Research projects; select thesis and adviser.

Year 3: Complete oral candidacy exam on proposed thesis before end of third term. Submit annual report to option representative. Ay 141. Optional Advanced Courses

Year 4: Submit annual report. Thesis Advisory Committee (TAC) check-in. Ay 141.

Year 5: Submit annual report. Thesis Advisory Committee (TAC) check-in. Ay 141. Complete Ph.D. thesis work and writing before the end of year 5. Final oral thesis defense.