The LABOCA Survey of the ECDFS – submm properties of NIR-selected galaxies Thomas R. Greve (MPIA), Axel Weiss, Attila Kovacs, Fabian Walter, Ian Smail, Peter Kurczynski & the rest of the LESS Team APEX LABOCA Charlottesville, September 2009

E-CDFS: 30’ x 30’ field Ra 03:30h Dec -27:40 deg Wavelength coverage: X-ray: Chandra, XMM UV: GALEX Opt: MUSYC, HST GEMS/GOODS, COMBO-17 IR: SIMPLE (IRAC), FIDEL (MIPS) Radio: VLA 1.4GHz 30’ LABOCA-ECDFS Survey - The Field HSTChandra Milky Way HI E-CDFS GOODS-south

LABOCA-ECDFS Survey - Instrument LABOCA: Wavelength: 870 µm Bandwidth: 60 GHz Resolution: 19.2’’ FoV: 10.4’ Pixels: ~250 Sensitivity: 50 mJy √s

Map rms after 280hrs on source:  =1.2 mJy/b (beam smoothed) Same area but ~2 lower noise level than largest SCUBA survey (SHADES) LABOCA-ECDFS Survey - Noise Properties rms map ECDFS Shades 1.1 mJy/b 1.2 mJy/b

Weiss et al. (2010) LABOCA-ECDFS Survey – S/N map

What’s the nature of the submm faint (<0.5mJy) galaxies? Reverse strategy: select high-z galaxies populations at other wavelengths (than submm) and search for a statistical signal Infer average IR-luminosities, SFRs, EBL-contribution and SF-laws as a function of z and stellar mass

The zoo of near-IR selected galaxies Why the near-IR? near-IR selection is relatively immune to dust and age effects on the stellar population (unlike UV/optical) near-IR selection is essentially a stellar mass selection the near-IR is able to probe the low mass-end of galaxies compared to submm and radio surveys recent advent of large-format near-IR cameras Near-IR surveys have revealed populations of star forming galaxies and very old, red galaxies at 1 < z < 3, e.g. ERO, DRG, BzK Galaxies

The Multi-wavelength Yale-Chile Survey UBVRIzJHK imaging covering the entire ECDF-S (30’x30’) 5sigma AB limiting magnitudes: U (26.8) B (27.0) V (26.6) R (26.4) I (24.7) z (24.0) J (23.0) H (21.6) K (22.3) Ready-to-go catalogues available on-line K-selected sample: K vega ≤ 20 We also extracted BzK, ERO & DRG samples (selected down to K vega ≤ 20)

BzK Galaxies (star forming and passive) - selection sBzK (z-K) AB - (B-z) AB ≥ -0.2 pBzK (z-K) AB - (B-z) AB < -0.2 STARS

EROs and DRGs - selection STARS ERO (R-K) AB > 3.35 DRG (J-K) AB > 1.32

Final Catalogues STARS ERO (R-K) AB > 3.35 DRG (J-K) AB > 1.32 K vega  20: 8266 sBzK: 744 pBzK: 149 ERO: 1253 DRG: 737

Photometric Redshifts Phot-z’z are derived using EAZY code (Brammer, van Dokkum & Coppi 2008) Applied to the UBVRIzJHK MUSYC photometry σ(Δz) = z < 1.5 σ(Δz) = z > 1.5

Stellar masses Derived using Hyper-z on the UBVRIJHK (MUSYC) + IRAC (SIMPLE) photometry Bruzual & Charlot +03: SPP, Exp (300) and Constant SF histories. Calzetti dust (Av = 0-3) Use rest-frame H-band luminosity since M/L H is less sensitive to AGN and TP-AGB stars

Submm Stacking of K-selected galaxies Remove robust submm sources in map Go to positions of near-IR selected galaxies in the submm map and read of the signal and noise Weighted mean stacked flux and noise Deblending

Submm Stacking of K-selected galaxies

Full stacks… 3x 5x

Average 870μm flux vs. redshift for K vega ≥ 20 selected galaxies Submm Stacking of K-selected galaxies IR luminosities: sBzK:(2-6)x10 11 L  pBzK: (1-3)x10 11 L  ERO: (1-4)x10 11 L  DRG: (1-4)x10 11 L  Star formation rates: sBzK:(30-100)M  yr -1 pBzK: (10-50)M  yr -1 ERO: (20-60)M  yr -1 DRG: (20-60)M  yr -1 Background resolved: K vega < 20: 15% sBzK/ERO/DRG: ~4% (each)

Submm Stacking of K-selected galaxies As a function of 24μm flux (using the FIDEL MIPS catalogue: > 27μJy 5-σ) 24μm detected sources have 5x higher average 870μm flux than 24μm non- detections Linear correlation (S 24μm < 350μJy): S 870μm = 4.5x10 -3 x S 24μm “Flattening” at S 24μm > 350μJy 24μm traces starformation, but significant contribution from AGN for very bright 24μm systems (although selection function is non- trivial).

Stacking across the BzK-diagram Refining the sBzK/pBzK selection criteria?

SSFR vs. z and M star – evidence of downsizing? Total SFR (UV+FIR)

Summary The largest submm stacking analysis of K-selected galaxies, allowing us to probe 7x deeper than typical blank field submm surveys Significant submm signals for sBzK, ERO and DRG galaxies. pBzKs are not detected (<0.3mJy). Typically: L IR = (2-6)x10 11 L  and SFR = (60-100)M  yr -1 We find a strong increase in the submm-flux (star formation rate) of near-IR selected galaxies at z > 1.5. This means the dust-enshrouded star formation rate was higher at earlier cosmic epochs We find a linear 870μm-24μm correlation for S 24μm < 350μJy, suggesting that 24μm is a good tracer of starformation for such systems. For brighter 24μm systems the relation flattens, consistent with an AGN contribution to the 24μm flux Tentative evidence of SSFR-evolution with redshift. Also for downsizing, meaning less massive galaxies have higher SSFRs. This is the first time this kind of work has been done using the submm! See also poster by Peter Kurczynski