Spectroscopy in Spectroscopy in Cosmology and Galaxy Cosmology and Galaxy

EvolutionEvolution2005-20152005-2015

Conference SummaryConference SummaryMichael Strauss

Princeton University

There are many imaging There are many imaging surveys planned in the surveys planned in the

optical (e.g., Pan-STARRS, optical (e.g., Pan-STARRS, VISTA, LSST), and near-IR VISTA, LSST), and near-IR

(UKIDSS, DUNE)(UKIDSS, DUNE) People here don’t need convincing that real People here don’t need convincing that real

spectroscopy is at least as valuable.spectroscopy is at least as valuable. It is through spectra that we determine the It is through spectra that we determine the

astrophysics of individual objects. astrophysics of individual objects. But photo-But photo-z’z’s remain powerful, as argued by s remain powerful, as argued by

Wolf, Hildenbrandt, Wolf, Hildenbrandt, and and BenítezBenítez. . The combination of imaging and spectroscopy is The combination of imaging and spectroscopy is

particularly valuable (indeed, crucial, says particularly valuable (indeed, crucial, says GunnGunn). One can use cross-correlation of the two ). One can use cross-correlation of the two to constrain redshift distributions (to constrain redshift distributions (NewmanNewman). ).

Spectra “good enough Spectra “good enough for a redshift”? for a redshift”?

Focussed surveys to get redshifts only can Focussed surveys to get redshifts only can go much quicker than more go much quicker than more comprehensive projects (PRIMUS, ADEPT, comprehensive projects (PRIMUS, ADEPT, HETDEX, FASTSOUND). This is a fine HETDEX, FASTSOUND). This is a fine approach to baryon oscillation projects. approach to baryon oscillation projects.

But high S/N spectra are tremendously But high S/N spectra are tremendously valuable for stellar populations, M/L, ages, valuable for stellar populations, M/L, ages, star formation rate, metallicities, velocity star formation rate, metallicities, velocity dispersions, emission-line diagnostics, dispersions, emission-line diagnostics, AGN activity (AGN activity (Thomas, meThomas, me), serendipity… ), serendipity…

SerendipitySerendipity……

Ly emitters in DEEP2; Davis

Gravitationally lensed galaxies behind LRGs; Bolton

We’re never satisfied We’re never satisfied with the quality of with the quality of spectra we have…spectra we have… Excellent spectrophotometry was emphasized by Excellent spectrophotometry was emphasized by

Panter and others. Panter and others. Broad wavelength coverage, including NIR and Broad wavelength coverage, including NIR and

into Spitzer bands (into Spitzer bands (Maraston, GunnMaraston, Gunn). The advent ). The advent of FMOS and SIDE are particularly exciting here. of FMOS and SIDE are particularly exciting here.

High S/N, even for faint objects, as emphasized High S/N, even for faint objects, as emphasized by by Smith, ChilingarianSmith, Chilingarian, and others. , and others.

High resolution (R=5000), to study dwarfs, and High resolution (R=5000), to study dwarfs, and to resolve the OH forest. to resolve the OH forest.

Studies of environment effects on galaxy Studies of environment effects on galaxy properties, especially clusters (properties, especially clusters (Wolf, Wolf, Maurogordato, Khochfar, Tanaka, KovacMaurogordato, Khochfar, Tanaka, Kovac).).

We also need spatially resolved We also need spatially resolved spectroscopy of galaxies!spectroscopy of galaxies!

The aperture effects in SDSS are The aperture effects in SDSS are severe, making it difficult to severe, making it difficult to compare spectra at low and high compare spectra at low and high redshifts. redshifts.

There is much to be learned from There is much to be learned from internal kinematics of galaxies, as, internal kinematics of galaxies, as, e.g., the SAURON survey has shown e.g., the SAURON survey has shown us for nearby ellipticals. Multiple us for nearby ellipticals. Multiple deployable IFU’s? (KMOS, also SIDE deployable IFU’s? (KMOS, also SIDE with micro-IFU’s). with micro-IFU’s).

At what redshift do we At what redshift do we want to work? want to work?

ShanksShanks argues that the argues that the zz<1 universe of galaxies is <1 universe of galaxies is “solved”. But we saw lots of reasons to study it in “solved”. But we saw lots of reasons to study it in more detail, including “archeology” via detailed more detail, including “archeology” via detailed spectral modelling of spectral modelling of zz~0 galaxies (~0 galaxies (Brinchmann, Brinchmann, Maraston, Panter, Kauffmann, Gonzàlez-DelgadoMaraston, Panter, Kauffmann, Gonzàlez-Delgado and others). and others).

We are still trying to understand observationally We are still trying to understand observationally the merger rate, and the drop in star formation the merger rate, and the drop in star formation rate since rate since zz~1 (~1 (TresseTresse). ).

We shouldn’t forget the archeology of studying We shouldn’t forget the archeology of studying our own Milky Way in detail, to learn about the our own Milky Way in detail, to learn about the formation of the galaxy we know best (SEGUE, formation of the galaxy we know best (SEGUE, RAVE, and other surveys). RAVE, and other surveys).

The high redshift The high redshift universe is interesting universe is interesting

too!too! Galaxy populations change dramatically at Galaxy populations change dramatically at zz>1.5. >1.5. We argue over the galaxy census at We argue over the galaxy census at zz=3 and its =3 and its connection to low redshift. connection to low redshift.

It is difficult work. Even getting redshifts at It is difficult work. Even getting redshifts at zz>1.4 requires wide wavelength coverage, >1.4 requires wide wavelength coverage, including NIR. Physical studies are even more including NIR. Physical studies are even more difficult, but are very important. It will be a long difficult, but are very important. It will be a long time before we can hope for SDSS-like spectra at time before we can hope for SDSS-like spectra at high high zz. .

VVDS (VVDS (Le FèvreLe Fèvre) and DEEP2 () and DEEP2 (DavisDavis) show we ) show we can do large surveys at can do large surveys at zz~1, but we’re still very ~1, but we’re still very cosmic-variance limited. cosmic-variance limited.

We heard almost nothing about surveys at We heard almost nothing about surveys at zz≥3.≥3.

Emission-line ratios are interestingly different at z=2-3 and z=0!

There is much work to be done on understanding UV spectra of galaxies (and stars!; Brinchmann, Heap), needed for high-z surveys.

We also haven’t We also haven’t mentioned other types of mentioned other types of

spectroscopy:spectroscopy: SKA: A neutral hydrogen SKA: A neutral hydrogen

spectroscopic census out to z~1: the spectroscopic census out to z~1: the cold gas component of galaxies. cold gas component of galaxies.

The IGM, as studied through the LyThe IGM, as studied through the Ly forest of quasars (or galaxies for the forest of quasars (or galaxies for the ELTs), or via UV emission detected ELTs), or via UV emission detected by dedicated telescopes (by dedicated telescopes (Tresse, Tresse, WhiteWhite). ).

BAO or galaxy studies?BAO or galaxy studies? Why is there a choice? Surveys like SDSS Why is there a choice? Surveys like SDSS

have shown that you can do cosmology and have shown that you can do cosmology and get spectra to study galaxy properties at the get spectra to study galaxy properties at the same time. This of course gets increasingly same time. This of course gets increasingly difficult as you get fainter…difficult as you get fainter…

BAO is a growth industry (BAO is a growth industry (Nichol, Schlegel, Nichol, Schlegel, Totani, ShanksTotani, Shanks). We can argue about ). We can argue about whether it is “fundamental” and where we whether it is “fundamental” and where we should put all our energy, but the should put all our energy, but the acceleration of the universe is an acceleration of the universe is an astronomically observed fact, and we need to astronomically observed fact, and we need to probe it in as many ways as we can. probe it in as many ways as we can.

Making surveys work: it Making surveys work: it is not just building an is not just building an

instrument!instrument! Line up funding in advance! (SDSS’ mistake…)Line up funding in advance! (SDSS’ mistake…) Get strong project management (another SDSS Get strong project management (another SDSS

mistake). mistake). Build your system with specific surveys in mind!Build your system with specific surveys in mind! Be patient. Be patient. Software is at least as important as the hardware. Software is at least as important as the hardware.

Don’t cut corners. Automate redshift estimation!Don’t cut corners. Automate redshift estimation! Those that build the hardware and the survey will be Those that build the hardware and the survey will be

too tired/busy to do the science; make sure young too tired/busy to do the science; make sure young people have plenty of opportunity and freedom to lead people have plenty of opportunity and freedom to lead the science analyses. And make sure that the the science analyses. And make sure that the community recognizes who did the work! (community recognizes who did the work! (Nichol, Nichol, WhiteWhite))

Outreach (Letterman, Google Earth…)Outreach (Letterman, Google Earth…)

Wide-field spectroscopy Wide-field spectroscopy in the futurein the future

We heard about many wonderful projects that will We heard about many wonderful projects that will soon get underway or are poposed: Wigglez, soon get underway or are poposed: Wigglez, FMOS , , zCOSMOS, WMOS, KMOS, SIDE, FMOS , , zCOSMOS, WMOS, KMOS, SIDE, BOSS, HETDEX (Sorry to Tom for the acronyms!)BOSS, HETDEX (Sorry to Tom for the acronyms!)

There are other related projects not discussed There are other related projects not discussed here: LAMOST, ADEPT, SPM, RAVE, SKA, here: LAMOST, ADEPT, SPM, RAVE, SKA, SPACE. No doubt I’m missing some important SPACE. No doubt I’m missing some important ones… ones…

The field will remain vibrant with the advent of The field will remain vibrant with the advent of the 20-40 meter telescopes (the 20-40 meter telescopes (CollessColless). Moreover, ). Moreover, there will be plenty of survey work to keep the 4- there will be plenty of survey work to keep the 4- and 8-meters busy for at least several decades. and 8-meters busy for at least several decades.

Let us close by thanking Paco, Antonio Let us close by thanking Paco, Antonio and Christian for organizing such a and Christian for organizing such a scientifically productive meeting in such scientifically productive meeting in such a beautiful and fascinating place!a beautiful and fascinating place!