First cycle
degree courses
Second cycle
degree courses
Single cycle
degree courses
School of Science
Course unit
SCN1032616, A.A. 2018/19

Information concerning the students who enrolled in A.Y. 2018/19

Information on the course unit
Degree course Second cycle degree in
SC1173, Degree course structure A.Y. 2010/11, A.Y. 2018/19
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Degree course track Common track
Number of ECTS credits allocated 6.0
Type of assessment Mark
Course unit English denomination ASTRONOMICAL SPECTROSCOPY
Website of the academic structure
Department of reference Department of Physics and Astronomy
Mandatory attendance
Language of instruction Italian
Single Course unit The Course unit can be attended under the option Single Course unit attendance
Optional Course unit The Course unit can be chosen as Optional Course unit

Teacher in charge STEFANO CIROI FIS/05

ECTS: details
Type Scientific-Disciplinary Sector Credits allocated
Core courses FIS/05 Astronomy and Astrophysics 6.0

Course unit organization
Period Second semester
Year 1st Year
Teaching method frontal

Type of hours Credits Teaching
Hours of
Individual study
Lecture 6.0 48 102.0 No turn

Start of activities 25/02/2019
End of activities 14/06/2019

Examination board
Board From To Members of the board
6 Commissione Spettroscopia Astronomica 17/18 01/10/2018 30/11/2019 CIROI STEFANO (Presidente)

Prerequisites: Basic knowledge of Physics 1 and 2, Mathematical Analysis 1 and 2, Atomic Physics, Astrophysics 1 and 2, Laboratory of Astronomy.
Target skills and knowledge: The course provides that the student acquires the fundamental and indispensable concepts for the understanding of the physical processes that lead to the formation of the emission-line spectrum. These concepts are the prerequisite for the analysis and subsequent interpretation of a spectrum emitted by an H II region and are applied in many sectors of observational astrophysics: emission-line stars, gaseous nebulae, star-forming regions and active galactic nuclei.
Examination methods: Oral exam on the topics discussed during the lectures. Foreign student can ask to do a written exam with open questions on the topics discussed during the lectures.
Assessment criteria: The assessment of the examination will be based on the following criteria:
1) full knowledge of the topics discussed during the lectures;
2) degree of understanding achieved by the student; the oral exam will not be a simple presentation of the required topics, but an active interview with the teacher; the written exam for foreign students will consist of specific questions that require detailed and detailed answers;
3) ability to follow reasonings proposed by the teacher during the interview; this last criterion valid for the oral exam will be used only as an added value for the final evaluation.
Course unit contents: 1) A brief introduction to spectroscopy as observational technique.
2) Characteristics of emission-line spectra: gaseous nebulae, Novae, Supernovae, Supernova remnants, star forming regions, active galactic nuclei.
3) The Boltzmann and the Saha equations.
4) The Radiative Transport Equation. The Equivalent Thermodynamic Equilibrium. Radiation density. Radiation transport in the lines. Deviations from thermodynamic equilibrium.
5) The cross-section of collisional interactions. The collisional efficiency rate.
6) Study of the population ratio in a two-level system. The two-level system in the optical range. Conditions for the emission of forbidden lines. The two-level system at radio frequencies. The H I 21 cm and the CO 2.6 mm lines. Line intensity as a function of density and temperature. Determination of the gas density and temperature.
7) Recombination lines. Population of the levels. Intensity of the optical recombination lines of H I. Intensity of the radio recombination lines.
8) Sources of continuous emission and absorption. Free-free transitions of thermal electrons. The thermal radio continuum. The synchrotron continuum. Bound-free and free-bound transitions in the optical-UV. Continuum emission from recombination. The 2-photons emission.
9) Statistical equilibrium in ionized nebulae. Radiative ionization and recombination. Ionization equilibrium in H II regions. The Stroemgren sphere. Stratification of ionization. H I regions. Cold dense and hot tenuous neutral cloud. Photoionization heating in H II regions. Cooling from metastable level transitions. Thermal equilibrium in H II regions.
10) Extinction by dust grains.
Planned learning activities and teaching methods: The course provides lectures in the classroom that include explanations on the blackboard for the theoretical part and video projections to show the observational data and the type of analysis that is carried out on them. Lectures are given in Italian.
Additional notes about suggested reading: Textbooks. Lecture notes of the teacher available through the website of the course on the e-learning platform of the Department of Physics and Astronomy "G. Galilei" (
Textbooks (and optional supplementary readings)
  • Osterbrock, Donald E., Astrophysics of gaseous nebulae and active galactic nuclei. Mill Valley, CA: University science books, 1989. Cerca nel catalogo
  • Emerson, Donald S., Interpreting astronomical spectra. Chichester: J. Wiley and sons, 1996. Cerca nel catalogo

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