We present a study of the connection between black hole accretion, star formation, and galaxy morphology at z ≤ 2.5. We focus on active galactic nuclei (AGNs) selected by their mid-IR power-law emission. By fitting optical to far-IR photometry with state-of-the-art spectral energy distribution (SED) techniques, we derive stellar masses, star formation rates, dust properties, and AGN contributions in galaxies over the whole COSMOS field. We find that obscured AGNs lie within or slightly above the star-forming sequence. We confirm our previous finding about compact host galaxies of obscured AGNs at z ∼ 1, and find that galaxies with 20-50% AGN contributions tend to have smaller sizes, by ∼25-50%, compared to galaxies without AGNs. Furthermore, we find that a high merger fraction of up to 0.5 is appropriate for the most luminous (log(L IR /L) ∼ 12.5) AGN hosts and non-AGN galaxies, but not for the whole obscured AGN sample. Moreover, merger fraction depends on the total and star-forming infrared luminosity, rather than the decomposed AGN infrared luminosity. Our results suggest that major mergers are not the main driver of AGN activity, and therefore obscured AGNs might be triggered by internal mechanisms, such as secular processes, disk instabilities, and compaction in a particular evolutionary stage. We make the SED modeling results publicly available.

We have carried out a survey of the north and south ecliptic poles, EP-N and EP-S, respectively, with the Spitzer Space Telescope and the Wide-field Infrared Survey Explorer (WISE). The primary objective was to cross-calibrate WISE with the Spitzer and Midcourse Space Experiment (MSX) photometric systems by developing a set of calibration stars that are common to these infrared missions. The ecliptic poles were continuous viewing zones for WISE due to its polar-crossing orbit, making these areas ideal for both absolute and internal calibrations. The Spitzer IRAC and MIPS imaging survey covers a complete area of 0.40 deg 2 for the EP-N and 1.28 deg 2 for the EP-S. WISE observed the whole sky in four mid-infrared bands, 3.4, 4.6, 12, and 22 μm, during its eight-month cryogenic mission, including several hundred ecliptic polar passages; here we report on the highest coverage depths achieved by WISE, an area of ∼1.5 deg 2 for both poles. Located close to the center of the EP-N, the Sy-2 galaxy NGC 6552 conveniently functions as a standard calibrator to measure the red response of the 22 μm channel of WISE. Observations from Spitzer-IRAC/MIPS/IRS-LL and WISE show that the galaxy has a strong red color in the mid-infrared due to star-formation and the presence of an active galactic nucleus (AGN), while over a baseline >1 year the mid-IR photometry of NGC 6552 is shown to vary at a level less than 2%. Combining NGC 6552 with the standard calibrator stars, the achieved photometric accuracy of the WISE calibration, relative to the Spitzer and MSX systems, is 2.4%, 2.8%, 4.5%, and 5.7% for W1 (3.4 μm), W2 (4.6 μm), W3 (12 μm), and W4 (22 μm), respectively. The WISE photometry is internally stable to better than 0.1% over the cryogenic lifetime of the mission. The secondary objective of the Spitzer-WISE Survey was to explore the poles at greater flux-level depths, exploiting the higher angular resolution Spitzer observations and the exceptionally deep (in total coverage) WISE observations that potentially reach down to the confusion limit of the survey. The rich Spitzer and WISE data sets were used to study the Galactic and extragalactic populations through source counts, color-magnitude and color-color diagrams. As an example of what the data sets facilitate, we have separated stars from galaxies, delineated normal galaxies from power-law-dominated AGNs, and reported on the different fractions of extragalactic populations. In the EP-N, we find an AGN source density of ∼260 deg −2 to a 12 μm depth of 115 μJy, representing 15% of the total extragalactic population to this depth, similar to what has been observed for low-luminosity AGNs in other fields.

We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of WISE-selected, hyperluminous galaxies, so called W1W2-dropout galaxies. This is a rare (∼ 1000 all-sky) population of galaxies at high redshift (peaks at z=2-3), that are faint or undetected by WISE at 3.4 and 4.6 µm, yet are clearly detected at 12 and 22 µm. The optical spectra of most of these galaxies show significant AGN activity. We observed 14 high-redshift (z > 1.7)W1W2-dropout galaxies with SHARC-II at 350 to 850 µm, with 9 detections; and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 µm, as well as optical spectra of 12 targets are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submm ratios than other galaxy templates, suggesting a hotter dust temperature. We estimate their dust temperatures to be 60 − 120 K using a single-temperature model. Their infrared luminosities are well over 10 13 L ⊙ . These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the Universe. We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.

We report the discovery by the Wide-field Infrared Survey Explorer of the z = 2.452 source WISE J181417.29+341224.9, the first hyperluminous source found in the WISE survey. WISE 1814+3412 is also the prototype for an all-sky sample of ∼ 1000 extremely luminous "W1W2-dropouts" (sources faint or undetected by WISE at 3.4 and 4.6 µm and well detected at 12 or 22 µm). The WISE data and a 350 µm detection give a minimum bolometric luminosity of 3.7 × 10 13 L ⊙ , with ∼ 10 14 L ⊙ plausible. Followup images reveal four nearby sources: a QSO and two Lyman Break Galaxies (LBGs) at z = 2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission. Gravitational lensing is unlikely given the source locations and their different spectra and colors. The dominant LBG spectrum indicates a star formation rate ∼ 300M ⊙ yr −1 , accounting for ∼ < 10% of the bolometric luminosity. Strong 22 µm emission relative to 350 µm implies that warm dust contributes significantly to the luminosity, while cooler dust normally associated with starbursts is constrained by an upper limit at 1.1 mm.-2 -Radio emission is ∼ 10× above the far-infrared/radio correlation, indicating an active galactic nucleus is present. An obscured AGN combined with starburst and evolved stellar components can account for the observations. If the black hole mass follows the local M BH -bulge mass relation, the implied Eddington ratio is ∼ > 4. WISE 1814+3412 may be a heavily obscured object where the peak AGN activity occurred prior to the peak era of star formation.Subject headings: galaxies: individual (WISE J181417.29+341224.9 ) WISE survey, and may be missed in surveys with substantially smaller areas by e.g., Spitzer and Herschel. Here we report on WISE J181417.29+341224.9 (hereafter WISE 1814+3412), the first hyper-luminous infrared galaxy (L IR > 10 13 L ⊙ ) discovered by WISE.Magnitudes are converted to flux densities using zeropoint values of 3631 Jy for the AB system g' and r' bands. Other magnitudes are on the Vega system, using zeropoints of 1594 and 666.7 Jy for the 2MASS system J and K s bands; 280.9 and 179.7 Jy for Spitzer IRAC [3.6] and [4.5]; and 306.7, 170.7, 29.04 & 8.284 Jy for WISE W1 through W4 respectively (Wright et al. 2010). Luminosities are calculated assuming Ω M = 0.3, Ω Λ = 0.7, and H 0 = 70 km s −1 Mpc −1 . Selection Criteria and Followup ObservationsEarly searches for the most luminous galaxies with WISE data included the investigation of outlier populations, among them objects which were only well detected in W3 and W4, including WISE 1814+3412. This approach proved highly successful (Figure 1), leading to a variety of followup programs now underway on sources which are much fainter in W1 (3.4 µm) and W2 (4.6 µm) than W3 (12 µm) or W4 (22 µm). The selection criteria for these "W1W2-dropouts" are W1 > 17.4 (< 34 µJy), and either: a) W4 < 7.7 (> 6.9 mJy) and W2 − W4 > 8.2; or b) W3 < 10.6 (> 1.7 mJy) and W2 − W3 > 5.3. W1W2-dropouts must also have at least 7 individual WISE exposures available for measurement in W3 or...

We present ground-based spectroscopic verification of 6 Y dwarfs (see also Cushing et al.), 89 T dwarfs, 8 L dwarfs, and 1 M dwarf identified by the Wide-field Infrared Survey Explorer (WISE). Eighty of these are cold brown dwarfs with spectral types T6, six of which have been announced earlier by Mainzer et al. and Burgasser et al. We present color-color and color-type diagrams showing the locus of M, L, T, and Y dwarfs in WISE color space. Near-infrared and, in a few cases, optical spectra are presented for these discoveries. Near-infrared classifications as late as early Y are presented and objects with peculiar spectra are discussed. Using these new discoveries, we are also able to extend the optical T dwarf classification scheme from T8 to T9. After deriving an absolute WISE 4.6 μm (W2) magnitude versus spectral type relation, we estimate spectrophotometric distances to our discoveries. We also use available astrometric measurements to provide preliminary trigonometric parallaxes to four of our discoveries, which have types of L9 pec (red), T8, T9, and Y0; all of these lie within 10 pc of the Sun. The Y0 dwarf, WISE 1541−2250, is the closest at 2.8 +1.3 −0.6 pc; if this 2.8 pc value persists after continued monitoring, WISE 1541−2250 will become the seventh closest stellar system to the Sun. Another 10 objects, with types between T6 and >Y0, have spectrophotometric distance estimates also placing them within 10 pc. The closest of these, the T6 dwarf WISE 1506+7027, is believed to fall at a distance of ∼4.9 pc. WISE multi-epoch positions supplemented with positional info primarily from the Spitzer/Infrared Array Camera allow us to calculate proper motions and tangential velocities for roughly one-half of the new discoveries. This work represents the first step by WISE to complete a full-sky, volume-limited census of late-T and Y dwarfs. Using early results from this census, we present preliminary, lower limits to the space density of these objects and discuss constraints on both the functional form of the mass function and the low-mass limit of star formation.