Commission J1 Galaxy Spectral Energy Distributions

Scientific Objectives

In the present era of ample access to observations covering the whole spectral range – from Gamma and X-ray wavelengths to radio wavelengths – it is possible to have a panchromatic view of galaxies and to derive their panchromatic  SEDs. A SED provides a concise “summary” of a galaxy content. However, underneath this brevity, a wide variety of physical processes are at play that shape these SEDs. 

All the components of a galaxy (gas, stars, dust…), as well an active galactic nucleus (AGN), contribute to this emission. Like that of any investigator, the astrophysicist’s dream is to try and determine, as best as possible, the physical characteristics of the emitter(s). To meet this goal, we have to gather data over the widest spectral range possible in order to obtain information on the many physical processes that are taking place. Interpreting these data requires understanding the likely contributors to the SED of an observed galaxy and its supermassive black hole.

The first phase of any such analysis is to model the emission of these contributors over the widest range of physical conditions possible. This is why this commission is linked to the “Stars and Stellar Physics” division, as the stellar component is a main one in galaxies. Moreover, it is related to the “Interstellar Matter and Local Universe” division, because of the gas and dust components and all the detailed processed that can only be studied in the Local Universe. And since a complete understanding of a make up of a galaxy is ultimately connected to the high energetic processes, we are also connected with the "High Energy Phenomena and Fundamental Physics" Division. The primary division is “Galaxies and Cosmology”.

The justification for a SED Commission is to provide a link, a connection, a (virtual) meeting room for astronomers around the world interested in galaxy SEDs without putting limits on time or space.

The communities that would be interested in participating and sharing their efforts are numerous, because of the impact of galaxy SEDs in astrophysics. Reiterating again that SEDs are multi-wavelength in nature, it is important to combine data secured by ground-based and space-based telescopes from the past, with those from current facilities and, in the future from facilities like JWST, SKA, LSST, EUCLID, ATHENA, ELTs, CTA, etc.  We absolutely need to discuss, develop and disseminate tools, models and, of course, new ideas in advance in order to be ready for the challenges that will be brought by these instruments and others.

We list a few of them that are certainly not exhaustive and may be under-representative:

* Multi-wavelength observations of galaxies (at all scales and at all redshifts)

* Building SSPs used in population synthesis

* Modeling the emission of stars, dust, AGN, gas and cosmic rays

* Constraining the formation and evolution of galaxies: which parameters, what methods, what bias/degeneracies?

* SED/SLED fitting

* galaxy templates for photometric redshifts

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