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GALEX Evolution Explorer An Imaging and Spectroscopic Survey

Mapping the formation history of the

Overview Selected First Results: The UV Galaxy Luminosity Function

Moriond Conference March 29, 2004 La Thuile, Italy

Ted K. Wyder Caltech GALEX Science Team Caltech Johns Hopkins U. LAM (Marseille) Peter Friedman Tim Heckman Bruno Milliard David Schiminovich Luciana Bianchi Jose Donas Tom Barlow David Thilker Marie Treyer Ted Wyder Charles Hoopes Veronique Buat Patrick Morrissey Alex Szalay Dennis Bugarella Kevin Xu Tamas Budavari Michele Laget Todd Small UC Los Angeles J.M. Deharveng Karl Forster Mike Rich Roger Malina Chris Martin (PI) Samir Salim CIW Mark Siebert Yonsei Univ Barry Madore UC Berkley Young-Wook Lee A. Gil de Paz Ossie Siegmund Yong-Ik Byun MPI (Garching) Barry Welsh Suk Young-Yi Guinevere Kauffman

Shauna Sallmen Chang Rhee Stephane Charlot GALEX Characterisitcs

Effective Area 20-50 cm2

60 Im 50 Angular resolution 4.5-6” FWHM Im ) 2

^ 40 m f (c f 30 Sp Spectral Resolution 100-250 e _ A 20 [grism mode] Sp 10 Field of View 1.2 degrees

0 1300 1800 2300 2800 Bands FUV λ ~ 1540 A λ (Angstroms) NUV λ ~ 2300 A [simultaneous] Sensitivity 100 s 20.5 [AIS] (AB mag) 1.5 ks 23.5 [MIS/NGS] 30 ks 25 [DIS] Observations Nightime 1 eclipse=1000-2000 s Mission Length Baseline 28 months Minimum 12 months Rest UV Traces

Young mass fraction:

10-1

10-7 GALEX Science Questions

Major questions that we plan to SFH of the universe (Madau et al. 1996, address with GALEX: 1998) ƒ How does the UV the global star formation rates in ? ƒ What is the star formation rate in galaxies and how does it evolve over 0 < z < 2? ƒ What are the physical drivers of star formation in galaxies over 0 < z < 2?

Sommerville, Primack & Faber 2001, MNRAS, 320, 504 All-sky Imaging Survey (AIS) Magnitude 20 AIS Mean 0.2 Redshift Area >10,000 deg

Cosmic Vol. 1 Gpc3

# Galaxies 10 Million

Z~0.2 Medium Imaging Survey (MIS) Magnitude 23 MIS Area 1000 deg2

Cosmic Vol. 1 Gpc3

Overlap SDSS, 2dF

# Galaxies 3 Million

Z~0.5

Z~0.2 Deep Imaging Survey (DIS) Magnitude 25 DIS Z~1.5 Area 80 deg2

Cosmic Vol. 1 Gpc3

Overlap CDFS, NOAO-DWS, SWIRE, VVDS, DEEPII, CFHTLS, … Z~0.5 # Galaxies 10 Million

Z~0.2 Nearby Galaxy Survey

Magnitude 27.5 mag M101 arcsec-2 NGS # Galaxies 200

Overlap SINGS, HI, Ha, Radio, … GALEX Guest Investigator Program

• Further information at : – http://galexgi.gsfc.nasa.gov – [email protected] • Proposals for: – Legacy programs – New observations – Archival investigations • Schedule: –NRA out – Proposals due April 16, 2004 – Cycle 1 starts October 2004 GALEX Science Questions

Major questions that we plan to SFH of the universe (Madau et al. 1996, address with GALEX: 1998) ƒ How does the UV trace the global star formation rates in galaxies? ƒ What is the star formation rate in galaxies and how does it evolve over 0 < z < 2? ƒ What are the physical drivers of star formation in galaxies over 0 < z < 2?

As a first step -- What is the UV luminosity function of galaxies in the local universe?

Wyder, Treyer, Milliard et. al. Sommerville, Primack & Faber 2001, MNRAS, (2004, in preparation) 320, 504 GALEX Fields in the 2dF-SGP Region

2dF Galaxy Redshift Survey: spectroscopic z’s for galaxies with BJ < 19.45 (Colless et al. 2001, MNRAS, 328 1039) selected from the APM catalog (Maddox et al. 1990, MNRAS, 243, 692)

Red points = Galaxies with redshifts from the 2dF survey Blue circles = GALEX AIS pointings Total overlap area used for our sample: 56.7 deg2 GALEX-2dF matched catalog

ƒ Matched 2dF and GALEX sources with 6 arcsec search radius ƒ Construct a magnitude-limited FUV sample with 17 < FUV < 20 Æ should be complete for galaxies with

(FUV – BJ) > 0.5 Redshift Completeness

ƒ Determine total galaxy counts from ~22.6 deg2 of overlap with the SDSS (Xu et al. 2004, in preparation)

ƒ Completeness = N2dF/NSDSS Redshift distribution Luminosity Function Calculation

β ƒ Compute k-corrections from the (FUV – NUV) color assuming fλ ~ λ ƒ No internal extinction correction

ƒ Determine the luminosity function from the Vmax method

φ = Σ (1/Vmax)

Schechter function (Schechter 1976):

α φ(L) dL = φ∗ (L/L*) exp{-L/L*} dL/L*

φ∗= normalization L*= characteristic luminosity α = faint end power law slope UV Luminosity Function for z<0.1 All values assume:

Ωmatter=0.3; ΩΛ=0.7; H0=70 km/sec/Mpc

Band log(φ∗) M* α FUV -2.30±0.05 -17.92±0.09 -1.17±0.07

NUV -2.20±0.05 -18.18±0.09 -1.17±0.06

FOCA -2.48±0.11 -19.10±0.13 -1.51±0.10

Schechter function: α φ(L) dL = φ∗ (L/L*) exp{-L/L*} dL/L*

-1 SFR ~ 4 M_solar yr for AUV=1.5 UV Luminosity Density

ρL = φ∗ L* Γ(α+2) FOCA: Sullivan et al. (2000, MNRAS, 312, 442)

Hawaii Survey Fields: Wilson et al. (2002, AJ, 124, 1258)

HDF: Connolly et al. (1997, ApJ, 486, L11) Pascarelle et al. (1998, ApJ, 508, L1)

CFRS: Lilly et al. (1996, ApJ, 460, L1) UV Luminosity Function vs. UV color Does the luminosity function depend upon the UV color of the galaxy? Do we see any evidence luminosity function evolution for z < 0.2? Treyer, Wyder, Milliard et al. (2004, in preparation)

β UV spectrum: fλ∝ λ Unreddened galaxy with constant SFR has β ≈ −2.2 or (FUV − NUV) ≈ −0.2 UV Luminosity functions for red and blue samples ƒ Separate luminosity functions for z<0.1 red : (FUV -- NUV) > 0.25 (older or more dust) blue : (FUV -- NUV) < 0.25 (younger or less dust) FUV Luminosity Function for 0.1

GALEX DIS -- 52760 sec reaching NUV ~ 24.5

black dots = GALEX objects with 1 optical counterpart within 4 arcsec

crosses = objects with more than one optical counterpart

red dots = objects with VVDS spectra

green dots = objects with

IAB<17.5

Arnouts, Schiminovich, et al. (2004, in preparation) GALEX-VVDS sample -- redshift distribution 1500 Ang. Luminosity Function evolution FUV Luminosity Density Evolution Summary o GALEX is a UV conducting various UV imaging and spectroscopic surveys o First science results: UV luminous galaxies, UV 2-pt correlation function, UV extinction in galaxies, star formation histories of galaxies, UV properties of nearby galaxies, Lyman continuum escape fraction, UV properties of AGN, ages of elliptical galaxies, RR Lyrae, dwarf novae, … o GALEX has a GI program with proposals due April 16, 2004. o We have measured a luminosity function in the local universe leading to a UV luminosity density (and hence SFR) lower than previous estimates. o The luminosity functions of galaxies with red UV colors have a shallower faint end slope and fainter M* than blue galaxies. o We detect evolution in the UV luminosity function even for z<0.2. o Using a sample of redshifts from the VVDS survey, we have measured the rest-FUV luminosity function out z~1.