Spitzer IRAC Confirmation of z850-Dropout Galaxies in the Hubble Ultra Deep Field: Stellar Masses and Ages at z ≈ 7

By I. Labbé, R. Bouwens, G. Illingworth, M. F. C. Observatories, U. S. Cruz, L. Observatory. 2006

137 citations recorded by the source corpus.

Using Spitzer IRAC mid-infrared imaging from the Great Observatories Origins Deep Survey, we study z850-dropout sources in the Hubble Ultra Deep Field. After carefully removing contaminating flux from foreground sources, we clearly detect two z850 dropouts at 3.6 and 4.5 μm, while two others are marginally detected. The mid-infrared fluxes strongly support their interpretation as galaxies at z ≈ 7, seen when the universe was only 750 Myr old. The IRAC observations allow us for the first time to constrain the rest-frame optical colors, stellar masses, and ages of the highest redshift galaxies. Fitting stellar population models to the spectral energy distributions, we find photometric redshifts in the range 6.7-7.4, rest-frame colors U - V = 0.2-0.4, V-band luminosities LV = (0.6-3) × 1010 L☉, stellar masses (1-10) × 109 M☉, stellar ages 50-200 Myr, star formation rates up to ~25 M☉ yr-1, and low reddening AV < 0.4. Overall, the z = 7 galaxies appear substantially less massive and evolved than Lyman break galaxies or distant red galaxies at z = 2-3, but fairly similar to recently identified systems at z = 5-6. The stellar mass density inferred from our z = 7 sample is ρ* = 1.6 × 106 M☉ Mpc-3 (to 0.3L), in apparent agreement with recent cosmological hydrodynamic simulations, but we note that incompleteness and sample variance may introduce larger uncertainties. The ages of the two most massive galaxies suggest that they formed at z ≳ 8, during the era of cosmic reionization, but the star formation rate density derived from their stellar masses and ages is not nearly sufficient to reionize the universe. The simplest explanation for this deficiency is that lower mass galaxies beyond our detection limit reionized the universe.

Subfields: Astronomy and Astrophysics, Instrumentation

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In Astronomy and Astrophysics

1. P. V. van Dokkum
2. M. Franx
3. P. Hopkins
4. L. Hernquist
5. Richard S. Ellis
6. I. Labbé
7. R. Somerville
8. R. Bouwens

In Instrumentation

1. P. V. van Dokkum
2. M. Franx
3. I. Labbé
4. Richard S. Ellis
5. R. Bouwens
6. C. Conroy
7. G. Illingworth
8. P. Oesch

Citations in the corpus

• Hubble Space Telescope and Spitzer Imaging of Red and Blue Galaxies at z ~ 2.5: A Correlation between Size and Star Formation Activity from Compact Quiescent Galaxies to Extended Star-forming Galaxies (2007, methodology): “The data reduction and photometry were carried out in a similar way as in Labbé et al. (2006) andWuyts et al. (2007), and details of the data reduction and photometry method are described in I. Labbé et al. (2008, in preparation).”
• A CENSUS OF STAR-FORMING GALAXIES IN THE Z ∼ 9–10 UNIVERSE BASED ON HST+SPITZER OBSERVATIONS OVER 19 CLASH CLUSTERS: THREE CANDIDATE Z ∼ 9–10 GALAXIES AND IMPROVED CONSTRAINTS ON THE STAR FORMATION RATE DENSITY AT Z ∼ 9.2 (2012, methodology): “Here we make use of the Mophongo software (Labbé et al. 2006, 2010a, 2010b, 2013) to do photometry on sources in our fields, given the confusion.”
• Evolution of the Intergalactic Opacity: Implications for the Ionizing Background, Cosmic Star Formation, and Quasar Activity (2008, background): “Stellar mass density measurements at z & 5 (e.g., Labbé et al. 2006; Yan et al. 2006; Eyles et al. 2007; Stark et al. 2007a) also suggest significant early star formation.”
• THE DEAD SEQUENCE: A CLEAR BIMODALITY IN GALAXY COLORS FROM z = 0 to z = 2.5 (2009, methodology): “We measure fluxes at 24 µm from Spitzer -MIPS images provided by the S-COSMOS and FIDEL9 surveys using a source-fitting routine that is designed to address confusion issues in the broad-PSF MIPS images (Labbé et al. 2006; see Wuyts et al. 2007 for an illustrative example).”
• Galaxies at z = 6 - 9 from the WFC3/IR imaging of the HUDF (2009, background): “2, this pointing lies somewhat to the north of the existing NICMOS F110W and F160W imaging within the HUDF (Thompson et al. 2005), and the deep VLT ISAAC K′-band image referred to by Labbe et al. (2006) (which reaches a5σ detection limit ofK′(AB) ≃ 25.5).”
• THE SPECTRAL ENERGY DISTRIBUTIONS OF z ∼ 8 GALAXIES FROM THE IRAC ULTRA DEEP FIELDS: EMISSION LINES, STELLAR MASSES, AND SPECIFIC STAR FORMATION RATES AT 650 MYR (2012, methodology): “…been taken as evidence of substantial stellar masses ∼ 109 − 1010M⊙ (Eyles et al. 2005; Yan et al. 2006; Stark et al. 2009) and stellar ages (> 300Myr) (Labbé et al. 2006; González et al. 2010; 1 Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the…”
• 3D-HST WFC3-SELECTED PHOTOMETRIC CATALOGS IN THE FIVE CANDELS/3D-HST FIELDS: PHOTOMETRY, PHOTOMETRIC REDSHIFTS, AND STELLAR MASSES (2014, methodology): “We use the code developed by one of us (I. Labbé) to perform the photometry on the ground-based and Spitzer IRAC images, as described in Labbé et al. (2006); Wuyts et al. (2007); Whitaker et al. (2011).”
• THE SFR–M* RELATION AND EMPIRICAL STAR FORMATION HISTORIES FROM ZFOURGE AT 0.5 < z < 4 (2015, methodology): “Therefore we use the Multi-Resolution Object PHotometry oN Galaxy Observations (MOPHONGO) code written by I. Labbé to extract deblended photometry in these farIR data (for a detailed discussion see Labbé et al. 2006; Wuyts et al. 2007).”
• THE STELLAR MASS DENSITY AND SPECIFIC STAR FORMATION RATE OF THE UNIVERSE AT z ∼ 7 (2009, methodology): “We find a fiducial value that is a about half the one estimated by Labbé et al. (2006).”
• KECK SPECTROSCOPY OF 3 < z < 7 FAINT LYMAN BREAK GALAXIES: THE IMPORTANCE OF NEBULAR EMISSION IN UNDERSTANDING THE SPECIFIC STAR FORMATION RATE AND STELLAR MASS DENSITY (2012, background): “…spectral energy distributions (SEDs) for thousands of galaxies spanning the redshift range 3 < z < 7 (e.g., Egami et al. 2005; Eyles et al. 2005; Labbé et al. 2006; Eyles et al. 2007; Stark et al. 2007, 2009; Ono et al. 2010; González et al. 2010; Labbé et al. 2010a,b; González et al.…”
• Structure and Star Formation in Galaxies out to z = 3: Evidence for Surface Density Dependent Evolution and Upsizing (2008, methodology): “As the PSFs of the other data sets were significantly worse, the PSF convolution and fitting technique of Labbé et al. (2006) and Labbé, (in preparation) was used to derive colors in the remaining bands.”
• CONSTRAINING THE LOW-MASS SLOPE OF THE STAR FORMATION SEQUENCE AT 0.5 < z < 2.5 (2014, methodology): “…11 http://irsa.ipac.caltech.edu/data/SPITZER/docs/mips/ mipsinstrumenthandbook/50/ perform the photometry on the low-resolution MIPS images (see earlier work by Labbé et al. 2006; Wuyts et al. 2007; Marchesini et al. 2009; Williams et al. 2009; Whitaker et al. 2011).”
• THE NEWFIRM MEDIUM-BAND SURVEY: PHOTOMETRIC CATALOGS, REDSHIFTS, AND THE BIMODAL COLOR DISTRIBUTION OF GALAXIES OUT TO z ∼ 3 (2011, methodology): “We use a source-fitting algorithm developed by one of us (IL) that is designed for heavily confused images to extract the photometry from the IRAC and MIPS images (see, e.g., Labbé et al. 2006; Wuyts et al. 2007; Marchesini et al. 2009; Williams et al. 2009).”
• THE NUMBER DENSITY AND MASS DENSITY OF STAR-FORMING AND QUIESCENT GALAXIES AT 0.4 ⩽ z ⩽ 2.2 (2011, methodology): “Fluxes and errors are then measured for each object with simple aperture photometry after subtracting the model of all neighboring objects (Labbé et al. 2006; see Wuyts et al. 2007 for an illustrative example).”
• z ~ 7-10 Galaxies in the HUDF and GOODS Fields: UV Luminosity Functions (2008, background): “As has already been discussed in Bouwens & Illingworth (2006) and Labbé et al. (2006), two of those candidates (UDF-818-886 and UDF-491-880) were the direct result of the “Mr. Staypuft” anomaly (Skinner et al. 1998), which produces faint electronic ghosts 128 pixels from bright stars.”
• A Keck Survey for Gravitationally Lensed Lyα Emitters in the Redshift Range 8.5 < z < 10.4: New Constraints on the Contribution of Low-Luminosity Sources to Cosmic Reionization (2007, background): “While a few candidate Lymanbreak galaxies beyond z ≃ 7 have been suggested from photometric data (Bouwens et al. 2005; Labbé et al. 2006; Richard et al. 2006; Bouwens & Illingworth 2006; Henry et al. 2007), none has yet been spectroscopically confirmed, due largely to the difficulties inherent to…”