Extragalactic AO ScienceExtragalactic AO Science

James LarkinJames Larkin

AOWG Strategic Planning MeetingAOWG Strategic Planning Meeting

September 19, 2004September 19, 2004

Fundamental motivationsFundamental motivations Galaxies quickly shrink below 1” in size making ground-based Galaxies quickly shrink below 1” in size making ground-based

observations difficult, but their sub-structures like bulges remain observations difficult, but their sub-structures like bulges remain above the Keck diffraction limit to arbitrary redshift.above the Keck diffraction limit to arbitrary redshift.

0

0.5

1

1.5

2

0 1 2 3 4 5

Redshift

An

gu

lar

Siz

e(a

rcsec)

5 kpc

2 kpc

0.5 kpc

Good Optical/NIR Seeing

Keck Diffraction Limit @ 1.6m

M=0.25, =0.75, Ho=70 km/s/Mpc

1”

Sb Galaxy @ z=0.5

Fundamental motivationsFundamental motivations At high redshift, optical spectral lines shift into the infrared where At high redshift, optical spectral lines shift into the infrared where

AO correction is best and HST has had limited impact.AO correction is best and HST has had limited impact. Magic redshift ~ 2.3Magic redshift ~ 2.3

HH & NII in K band & NII in K band OIII & HOIII & H in H band in H band OII, 4000 Break in J bandOII, 4000 Break in J band This is probably the formation epoch of MW-like disks (1” diameter).This is probably the formation epoch of MW-like disks (1” diameter).

Most gravitational lenses occur in areas under a couple of Most gravitational lenses occur in areas under a couple of arcseconds, and weakly lensed galaxies are elongated by of order arcseconds, and weakly lensed galaxies are elongated by of order an arcsecond.an arcsecond.

Even for extended sources, AO on Keck provides increased Even for extended sources, AO on Keck provides increased sensitivity. Especially powerful in identifying point-like sources within sensitivity. Especially powerful in identifying point-like sources within galaxy.galaxy.

Crowding of stars in nearby systems prevents accurate analysis of Crowding of stars in nearby systems prevents accurate analysis of stellar populations.stellar populations.

The internal structure of most nearby active nuclei is unresolved The internal structure of most nearby active nuclei is unresolved with one arcsecond resolution.with one arcsecond resolution.

Fundamental ProblemsFundamental Problems Guide star brightnessGuide star brightness

Very few galaxies have sufficiently bright cores for high-order Very few galaxies have sufficiently bright cores for high-order AO systems.AO systems.

Only ~10Only ~10-4-4 of objects are near bright foreground stars of objects are near bright foreground stars Curvature systems are currently doing most of the extragalactic Curvature systems are currently doing most of the extragalactic

science, but with limited Strehl.science, but with limited Strehl. Surface BrightnessSurface Brightness

Sensitivity increases rapidly with Strehl for point sources, but Sensitivity increases rapidly with Strehl for point sources, but extended targets gain much less.extended targets gain much less.

AO systems produce additional background in Near-IR and AO systems produce additional background in Near-IR and reduce throughput further making it difficult to observe faint reduce throughput further making it difficult to observe faint extended sources.extended sources.

Normal galaxy disks only achieve a maximum SB of K~16 Normal galaxy disks only achieve a maximum SB of K~16 mag/sq arcsec and this fades as (1+z)mag/sq arcsec and this fades as (1+z)44. This means all normal . This means all normal disks are fainter than 22.5 mag within 0.05x0.05”.disks are fainter than 22.5 mag within 0.05x0.05”.

Galaxy evolution improves this affect.Galaxy evolution improves this affect. Observations take hours even for imaging.Observations take hours even for imaging.

What will the laser do…What will the laser do… Provide consistent performance on variety of sources.Provide consistent performance on variety of sources. Allow for target selection by characteristics.Allow for target selection by characteristics. Open up HST deep fields and ground based redshift Open up HST deep fields and ground based redshift

fields.fields. Brightest star within ultra deep field is R~15 magBrightest star within ultra deep field is R~15 mag

Opens up the study of rare but important objects such as Opens up the study of rare but important objects such as Lyman-break galaxies, sub-mm galaxies, and Lyman-break galaxies, sub-mm galaxies, and ultraluminous infrared galaxies.ultraluminous infrared galaxies.

Allow studies of stellar populations as a controlled Allow studies of stellar populations as a controlled function of radius.function of radius.

Improves Strehl since extragalactic sources have Improves Strehl since extragalactic sources have depended on off-axis guide stars.depended on off-axis guide stars.

Generally beneficial to all areas of extragalactic science.Generally beneficial to all areas of extragalactic science.

What would higher order do for you What would higher order do for you without a laserwithout a laser

Reduce fraction of sky available, probably Reduce fraction of sky available, probably becoming totally dependent on foreground becoming totally dependent on foreground off-axis stars.off-axis stars.

Increased sensitivity to point sources, and Increased sensitivity to point sources, and better contrast.better contrast.

Probably only beneficial to a few areas of Probably only beneficial to a few areas of stellar population studies if still dependent stellar population studies if still dependent on natural guide stars.on natural guide stars.

Other areas that will benefit Other areas that will benefit extragalactic science…extragalactic science…

Cleaner (or better coatings) and colder AO systems, and Cleaner (or better coatings) and colder AO systems, and better throughput.better throughput. K–band is probably the most important filterK–band is probably the most important filter Local thermal background can devastate faint object work.Local thermal background can devastate faint object work.

Integral field spectroscopyIntegral field spectroscopy Avoids slit losses.Avoids slit losses. Samples complex geometry.Samples complex geometry. Multiplex advantage on resolved stellar populations.Multiplex advantage on resolved stellar populations. SINFONI is commissioned on VLT.SINFONI is commissioned on VLT.

9 out of 12 approved science verification programs are extragalactic9 out of 12 approved science verification programs are extragalactic

Some big questions future AO could Some big questions future AO could addressaddress

Assembly of galaxy masses. Complex kinematics at z~1, Assembly of galaxy masses. Complex kinematics at z~1, Lyman break kinematics at z~3. Modern mass disks at Lyman break kinematics at z~3. Modern mass disks at z~2?z~2?

Variations within NLR of individual AGN, and detailed Variations within NLR of individual AGN, and detailed comparisons of many AGN. Testing standard paradigm.comparisons of many AGN. Testing standard paradigm.

Evolutionary (or not) linkages between ULIRGS, Evolutionary (or not) linkages between ULIRGS, Quasars and normal galaxies.Quasars and normal galaxies.

Cosmological constant – High redshift type-Ia Cosmological constant – High redshift type-Ia supernovae.supernovae.

Formation of bulges and tie to central black hole.Formation of bulges and tie to central black hole. Central velocity dispersions in local galaxies.Central velocity dispersions in local galaxies. Bulge formation tied to quasar epoch?Bulge formation tied to quasar epoch? Test new CDM models of galaxy formation.Test new CDM models of galaxy formation.

Technology with biggest impact Technology with biggest impact

Laser, especially with faint TT magnitudesLaser, especially with faint TT magnitudesPSF Characterization (stability,telemetry)– PSF Characterization (stability,telemetry)–

accurate photometry and morphologyaccurate photometry and morphologyGeneral improvements: better wavefront General improvements: better wavefront

sensor CCD, faster reconstructor, cleaner sensor CCD, faster reconstructor, cleaner optics.optics.