The Extremely Red Objects in the CLASH Fields

The Extremely Red Galaxies in CLASH Fields

Xinwen Shu (CEA, Saclay and USTC)

CLASH 2013 Team meeting – September 16-18 2013, London, UK

Mapping the visible Universe

Bouwens et al 2012

1. Determine the CSFRD with different

SFR estimators up to z=11

2. Measure contributions by different

galaxy populations to the global CSFRD

at different redshifts

3. Link galaxy populations and dark

matter halos at different cosmic epochs

4. Build up an empirical picture for

galaxy formation and evolution

5. Understand physical mechanisms

driving galaxy evolution

starlight dustre-radiation

Reddy et al. 2011

UV luminosity density

dust-corrected SFR

At z > 3, the 4000A break is shifted to wavelengths λ > 1.6 μm, implying that the potentially oldest and/or most dusty galaxies at those redshifts could be missed even by deep near-IR surveys.

Mobasher et al. 2005

Steidel+03, Franx+02, Daddi+04

Color selection of high-z galaxies:

H-[3.6]>4

Dusty galaxies with an evolved stellar population at z>4

SMG 850 5 by Wang et al. (2009)‐

Completing the census of star formation and the assembling history of stellar mass densities

NIR dropout?

More sources of this kind displaying extremely red color H-[3.6]>4?

Four H-[3.6]>4 galaxies in GOODS/ERS (50 arcmin^2, Huang et al. 2011): Possibilities: 1.Very dusty SED at z~1-2 2.Old stellar population at z>4.5, the iceberg of a larger population of z > 3 galaxies?

Why CLASH data?1. Deep WFC3 H-band images (27.5, 5σ) over 25

clusters, covering nearly 120 square arcmin2. Deep IRAC ([3.6]+[4.5]um) imaging (5σ depth

>24 mag)3. Multi-wavelength HST+Spitzer observations

allow for constrains on the SED4. Cluster lensing helps to probe the intrinsically

faint candidates5. Wealth of existing and ongoing follow-up

observations in other bands

[4.5um]<24.4, 4sigmaH160w>27.5, 5sigma Totally 13 candidates with H-[4.5]>4 over 23 CLASH clusters, including 8 detected in H-band, and 5 not (~110 arcmin^2)

7/8 H-band detected sources with photometric redshift between z~3.7-5.1

CLASH data

z = 3.77AV = 1.5age = 1.58 Gyrt = 0.25 GyrM* = 1.0x1011 Msun

Av-redshift contour plane

z = 4.82AV = 1.1age = 1.0 Gyrt = 0.25 GyrM* = 8.9x1011 Msun Orz = 1.11AV = 7.8age = 25 Myrt = 0.1 GyrM* = 6.3x109 Msun,

F160w IRAC

Can Herschel be helpful to constrain the SED?

1

Comparison with Candels/UDS : Herschel puts constraint on the nature of extremely H-[4.5]>4 sources in the Candels/UDS field (in progress)

Evidence for the presence of dusty and old stellar population

8um 24um 100um 160um 250um 350um 500um

F606 F814 F125 F160 [3.6] um [4.5] umCandels/UDS

H-dropouts in the cluster MACS 0429: Overdensity or lensed multiple images?

Candels/UDS: 25/180 arcmin^2

GOODS/ERS: 4/50 arcmin^2

M0429: 4 /4.8 arcmin^2

z=4, confirmed from CO

Summary and future workSummary:1.We identified 13 extremely red H-[4.5]>4 galaxies in the CLASH fields (over 23 clusters)2.For 8 sources, SED fitting to the HST+IRAC photometry indicates that 5 of them are likely massive galaxies at z~4 (logM*~11.01-11.98), though very dusty low-z solutions cannot be ruled out.3.None of sources is detected with Herschel (but the data are shallow)4.One cluster (M0429) shows an overdensity of H-dropouts or lensed multiple images, but improved estimation on redshift is required, e.g., CO lines?

Future work: 5.Inspect whether the H-dropouts are lensed by clusters if they are at z~4.6.Compare the physical properties of the H-dropouts (z, mass, morphology, size, color, environment, etc) to that in other fields, e.g, CANDLES/UDS.7.Need to look at the 24um emission to check the possibility of obscured AGNs (from Leonidas’ mosaic?).4. Sub-millimeter follow-up with ALMA?, redshift and dust continuum

Access to ALMA time?!