The Diverse Properties of the Most Ultraviolet-Luminous

Galaxies Discovered by GALEX

Hoopes et al. 2007, ApJ. 173, 441

Presented by Natalie R. Hinkel14 November, 2008

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One Foot In Front of the Other

Motivation

GALEX, SDSS, and calculated properties

Finding UV-luminous galaxies

Data relationships (on color) and Lyman break galaxies

Comparisons to literature: Tremonti et al. ’04, Savaglio et al. ’05, Erb et al. ’06 (on white) and some of my own research (!!)

The moral of the story

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Why do we care....really?

The cosmological star formation history is important to understanding the universe. But there are different measurement techniques in the UV at various redshifts.

There are also more pointed questions: What have become of Lyman break galaxies? Are they a unique population? How is this information reflected in other high-z surveys?

While there have been similar studies, the data set and questions are unique.

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GALEX: redshift range 0 < z < 2 for ~107 galaxies, FUV band ( ) and NUV ( ), resolution 5”, UV from only massive stars SFR

SDSS (matching requirements): classified as a galaxy in DR3, AGNs removed, 0 < z < 3, 3σ FUV detections, u-band half-light radius r50, u

Shiny, Reflect-y Things

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!e! = 1528A,!! = 268A!e! = 2271A,!! = 732A

= 18,463 UV Galaxies

GALEX: L1530

SDSS: redshifts (and distances), ugriz magnitudes, r50, u

SED: stellar mass, star formation rate

Literature: emission-line fluxes, widths, metallicities

Give Me Numbers!

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I1530 =L1530

2! r250,u

Normalized contour plots of the whole survey.

Increasing SB with luminosity relationship.

Radius tends to increases with luminosity.

But there is population with much higher SB and smaller radius where

is true in both cases.

Galaxies Abound!

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FUVSurface Brightness vs. Luminosity

wee!

Half-light Radius vs. Luminosity

I1530 ! 108L! kpc"2

I1530 = 108L! kpc"2

I1530 = 109L! kpc"2

I1530 > 109L! kpc"2

Lyman Breaks Galaxies, Lyman Broke Galaxies, Lyman’s Broken Galaxies

The progenitors to this group of anomalous galaxies, by virtue of the high redshifts, have been difficult to study -- until now. (cue scary music)

UV-luminous galaxies (UVLGs) at high redshifts (z > 2), called LBGs, have low-to-moderate masses:

Their vigorous star formation contributes heavily to that of all the universe.

The luminosity is in the range:

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log M! = 9.5! 11.0M"

L1530 > 2 x1010L!

Zeno’s Paradox, Anyone?By using the established LBG mass and luminosity cutoffs, 215 nearby UVLGs are identified at 0.053 > z > 0.3.

Difference between general survey trend (~ constant) and UVLGs (decrease).

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FUV, SB vs. stellar mass

UVLGs

Subdivide the UVLGs with and high SFRs into a “compact” group (105) - although not all are possible LBG analogs. The rest are “large” UVLGs, or spiral galaxies (110).

UVLGs Can Do Anything

Low SB galaxies are the most massive. High SB are low-mass.

There is no correlation between luminosity and SB or half-light radius.

The compact UVLGs, with smaller radii, owe their luminosity to intense star formation.

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Half-light radius vs. Luminosity

LBGs(z = 3)

Pretty Colors

Both colors are correlated with SB.

Compact UVLGs are bluer since UV-optical colors are sensitive to high SFRs.

Ultimately, the NUV - r plot indicates that current SF is much stronger than the average star formation in the past.

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Blue

get it? get it?

Red

Blue

Blue

Red Color vs. SB

Wasn’t Built in a DayThe specific SFR compares current to past SF. The inverse yields the “galaxy building time.”

Galaxies with the highest SB have short building times (~1 Gyr). The largest are on the order of H0-1.From Spitzer, LBGs have a small fraction of older stars, meaning nearby LBG predecessors would be experiencing their first star burst -- short building time.

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FUV SB vs. specific SFR

LBGs

Questions, Comments, or Concerns

The technique of Tremonti et al. ’04 (T04) was used over the whole sample (contours).

Best-fit for the T04 at z ~ 0.1 and Savaglio et al. ’05 (S05) at z ~0.7 compared to the UVLGs.

What about T04 & S05?

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Metallicity vs. Mass

+ supercompact UVLGS● compact UVLGs o large UVLGs

T04

S05

Can’t Deny 57,000 Galaxies

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Tremonti ’04 SDSS~57,000 galaxies z ~ 0.1

Solar

MW

Some ID, please.

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~ 57,000 galaxies z ~ 0.1

metallicity

color

Wait....I’m not done

Galaxies range 108.8-10.8 M⦿

and 4Gyr (!) from 0.3 < z < 1.0 with no metallicity-redshift correlation....duh.

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calibrated T04

S05 z~0.7

S05 z~2.3

Canada-France Redshift SurveyGemini Deep Deep Survey

Including Team Keck Redshift Survey

The data crosses all redshift “lines” indicating different ages.

Just when you thought...

Metallicity by Erb et al. ’06 at z ~ 2 was calculated via NII/Hα (Pettini & Pagel ‘04).

Larger UVLGs have higher metallicities than super/compact UVLGs.

Outflows were thought to produce this trend, which preferentially strip lower mass galaxies, not mass-dependencies.

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+ supercompact UVLGS● compact UVLGs o large UVLGs

Erb06 T04

Almost...*pant*.....done

Erb06 binned 14/15 galaxies per data point - bars denote bin spread and error.

Ages span 3Gyr!!!

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T04 recalibrated z~0.1T04 mass binsErb ’06 mass bins z~2

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The Lesson Learned

Metallicity is higher for galaxies with lower SBs, the large UVLGs, since lower SB is coupled with higher mass.

Low metals correlate with LBG ancestors.

But are the UVLGs the same age?

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Metallicity from T04 vs. FUV SB

“Supercompact” is the WINNER!!

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The Last Dot/Line Graph

Figure 1 returns!! -- But with local star burst galaxies, blue compact dwarfs, & UVGs for comparison.

Only one has high FUV SB and FUV luminosity - this is VV 114, a known LBG analog.

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THANKS!

As my last, final, and awesomest journal club presentation ever - I would to thank my stupendously ridiculous boyfriend and my monkey of an officemate (Will). Thanks to the class and Rogier for not falling asleep (obviously, I wrote this ahead of time - you better not have disappointed me). Finally, a thank you to Frank Timmes and SESE for paying juuuuuust enough to eat.

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