Abstract
We present a catalog of 10,718 objects in the COSMOS field, observed through multi-slit spectroscopy with the Deep Imaging Multi-Object Spectrograph (DEIMOS) on the Keck II telescope in the ...wavelength range ∼5500–9800 Å. The catalog contains 6617 objects with high-quality spectra (two or more spectral features), and 1798 objects with a single spectroscopic feature confirmed by the photometric redshift. For 2024 typically faint objects, we could not obtain reliable redshifts. The objects have been selected from a variety of input catalogs based on multi-wavelength observations in the field, and thus have a diverse selection function, which enables the study of the diversity in the galaxy population. The magnitude distribution of our objects is peaked at
I
AB
∼ 23 and
K
AB
∼ 21, with a secondary peak at
K
AB
∼ 24. We sample a broad redshift distribution in the range 0 <
z
< 6, with one peak at
z
∼ 1, and another one around
z
∼ 4. We have identified 13 redshift spikes at
z
> 0.65 with chance probabilities < 4 × 10
−4
, some of which are clearly related to protocluster structures of sizes >10 Mpc. An object-to-object comparison with a multitude of other spectroscopic samples in the same field shows that our DEIMOS sample is among the best in terms of fraction of spectroscopic failures and relative redshift accuracy. We have determined the fraction of spectroscopic blends to about 0.8% in our sample. This is likely a lower limit and at any rate well below the most pessimistic expectations. Interestingly, we find evidence for strong lensing of Ly
α
background emitters within the slits of 12 of our target galaxies, increasing their apparent density by about a factor of 4.
Abstract
We use JWST NIRCam observations of the massive lensing cluster field A2744 to develop a red galaxy selection of
f
F444W
> 1
μ
Jy and
f
F444W
/
f
F150W
> 3.5 that picks out all nine >4.5
σ
...Atacama Large Millimeter/submillimeter Array 1.1 or 1.2 mm sources and 17 of the 19 >5
σ
SCUBA-2 850
μ
m sources in the covered areas. We show that by using the red galaxies as priors, we can probe deeper in the SCUBA-2 850
μ
m image. This gives a sample of 44 >3
σ
SCUBA-2 850
μ
m sources with accurate positions, photometric redshifts, and magnifications. To investigate why our red galaxy selection picks out the 850
μ
m sources, we next analyze an extended sample of 167 sources with
f
F444W
> 0.05
μ
Jy and
f
F444W
/
f
F150W
> 3.5. We find that the fainter
f
F444W
sources in this sample are too faint to be detected in the SCUBA-2 850
μ
m image. We also show that there is a strong drop between
z
< 4 and
z
> 4 (a factor of around 5) in the ratio of the far-infrared luminosity estimated from the 850
μ
m flux to the
ν
L
ν
d
(5000) at rest-frame 5000 Å. We argue that this result may be due to the high-redshift sources having less dust content than the lower-redshift sources.
Abstract We make a comparison of deep SCUBA-2 450 and 850 μ m imaging on the massive lensing cluster field A2744 with Atacama Large Millimeter/submillimeter Array (ALMA) 1.2 mm data. Our primary goal ...is to assess how effective the wider-field SCUBA-2 sample, in combination with red JWST priors, is for finding faint dusty star-forming galaxies (DSFGs) compared to the much more expensive mosaicked ALMA observations. We cross-match our previously reported direct (>5 σ ) SCUBA-2 sample and red JWST NIRCam prior-selected (>3 σ ) SCUBA-2 sample to direct ALMA sources from the DUALZ survey. We find that roughly 95% are confirmed by ALMA. The red priors also allow us to probe deeper in the ALMA image. Next, by measuring the 450 and 850 μ m properties of the full ALMA sample, we show that 46/69 of the ALMA sources are detected at 850 μ m and 24/69 are detected at 450 μ m in the SCUBA-2 images, with a total detection fraction of nearly 75%. All of the robust (>5 σ ) ALMA sources that are not detected in at least one SCUBA-2 band lie at 1.2 mm fluxes ≲0.6 mJy and are undetected primarily due to the higher SCUBA-2 flux limits. We also find that the SCUBA-2 detection fraction drops slightly beyond z = 3, which we attribute to the increasing 1.2 mm to 850 μ m and 1.2 mm to 450 μ m flux ratios combined with the ALMA selection. The results emphasize the power of combining SCUBA-2 data with JWST colors to map the faint DSFG population.
We present an integrated study of star formation and galactic stellar mass assembly from image to 1.5 and galactic metallicity evolution from image to 0.9 using a very large and highly ...spectroscopically complete sample selected by rest-frame NIR bolometric flux in the GOODS-N. We assume a Salpeter IMF and fit Bruzual & Charlot models to compute the galactic stellar masses and extinctions. We determine the expected formed stellar mass density growth rates produced by star formation and compare them with the growth rates measured from the formed stellar mass functions by mass interval. We show that the growth rates match if the IMF is slightly increased from the Salpeter IMF at intermediate masses ( similar to 10 M sub(image)). We investigate the evolution of galaxy color, spectral type, and morphology with mass and redshift and the evolution of mass with environment. We find that applying extinction corrections is critical when analyzing galaxy colors; e.g., nearly all of the galaxies in the green valley are 24 mum sources, but after correcting for extinction, the bulk of the 24 mum sources lie in the blue cloud. We find an evolution of the metallicity-mass relation corresponding to a decrease of image dex between the local value and the value at image in the 10 super(10)-10 super(11) M sub(image) range. We use the metallicity evolution to estimate the gas mass of the galaxies, which we compare with the galactic stellar mass assembly and star formation histories. Overall, our measurements are consistent with a galaxy evolution process dominated by episodic bursts of star formation and where star formation in the most massive galaxies (image10 super(11) M sub(image)) ceases at image because of gas starvation.
Abstract
We present the luminosity function (LF) for ultraluminous Ly
α
emitting galaxies (LAEs) at
z
= 6.6. We define ultraluminous LAEs (ULLAEs) as galaxies with
erg s
−1
. We select our main ...sample using the
g
′,
r
′,
i
′,
z
′, and NB921 observations of a wide-area (30 deg
2
) Hyper Suprime-Cam survey of the north ecliptic pole (NEP) field. We select candidates with
, NB921 ≤ 23.5, and
. Using the DEIMOS spectrograph on Keck II, we confirm 9 of our 14 candidates as ULLAEs at
z
= 6.6 and the remaining 5 as an active galactic nucleus at
z
= 6.6, two O
iii
λ
5007 emitting galaxies at
z
= 0.84 and
z
= 0.85, and two nondetections. This emphasizes the need for full spectroscopic follow-up to determine accurate LFs. In constructing the ULLAE LF at
z
= 6.6, we combine our nine NEP ULLAEs with two previously discovered and confirmed ULLAEs in the COSMOS field: CR7 and COLA1. We apply rigorous corrections for incompleteness based on simulations. We compare our ULLAE LF at
z
= 6.6 with LFs at
z
= 5.7 and
z
= 6.6 from the literature. Our data reject some previous LF normalizations and power-law indices, but they are broadly consistent with others. Indeed, a comparative analysis of the different literature LFs suggests that no LF is fully consistent with any of the others, making it critical to determine the evolution from
z
= 5.7 to
z
= 6.6 using LFs constructed in exactly the same way at both redshifts.
Abstract
Finding high-redshift (
z
≫ 4) dusty star-forming galaxies is extremely challenging. It has recently been suggested that millimeter selections may be the best approach since the negative ...K-correction makes galaxies at a given far-infrared luminosity brighter at
z
≳ 4 than those at
z
= 2–3. Here we analyze this issue using a deep Atacama Large Millimeter/submillimeter Array (ALMA) 2 mm sample obtained by targeting ALMA 870
μ
m priors (these priors were the result of targeting SCUBA-2 850
μ
m sources) in the GOODS-S. We construct prior-based 2 mm galaxy number counts and compare them with published blank field-based 2 mm counts, finding good agreement down to 0.2 mJy. Only a fraction of the current 2 mm extragalactic background light is resolved, and we estimate what observational depths may be needed to resolve it fully. By complementing the 2 mm ALMA data with a deep SCUBA-2 450
μ
m sample, we exploit the steep gradient with a redshift of the 2 mm–450
μ
m flux density ratio to estimate redshifts for those galaxies without spectroscopic or robust optical/near-infrared photometric redshifts. Our observations measure galaxies with star formation rates in excess of 250
M
⊙
yr
−1
. For these galaxies, the star formation rate densities fall by a factor of 9 from
z
= 2–3 to
z
= 5–6.
We present a table of redshifts for 2907 galaxies and stars in the 145 arcmin super(2) HST ACS GOODS-North, making this the most spectroscopically complete redshift sample obtained to date in a field ...of this size. We also include the redshifts, where available, in a table containing just under 7000 galaxies from the ACS area with image measured from a deep image image obtained with WIRCam on the CFHT, as well as in a table containing 1016 sources with NUVimage and 478 sources with FUVimage (there is considerable overlap) measured from the deep GALEX images in the ACS area. Finally, we include the redshifts, where available, in a table containing the 1199 24 mum sources to 80 muJy measured from the wider area Spitzer GOODS-North. The redshift identifications are greater than 90% complete to magnitudes of image, and image, and to 24 mum fluxes of 250 muJy. An extensive analysis of these data appear in a companion paper, but here we test the efficiency of color-selection techniques to identify populations of high-redshift galaxies and active galactic nuclei. We also examine the feasibility of doing tomography of the intergalactic medium with a 30 m telescope.
Abstract
We present a seven-band (
g
,
r
,
i
,
z
,
y
, NB816, NB921) catalog derived from a Subaru Hyper Suprime-Cam (HSC) imaging survey of the North Ecliptic Pole (NEP). The survey, known as ...HEROES, consists of 44 deg
2
of contiguous imaging reaching median 5
σ
depths of
g
: 26.5,
r
: 26.2,
i
: 25.7,
z
: 25.1,
y
: 23.9, NB816: 24.4, and NB921: 24.4 mag. We reduced these data with the HSC pipeline software
hscPipe
, and produced a resulting multiband catalog containing over 25 million objects. We provide the catalog in three formats: (1) a collection of
hscPipe
format forced photometry catalogs, (2) a single combined catalog containing every object in that data set with selected useful columns, and (3) a smaller variation of the combined catalog with only essential columns for basic analysis or low-memory machines. The catalog uses all the available HSC data on the NEP and may serve as the primary optical catalog for current and future NEP deep fields from instruments and observatories such as SCUBA-2, eROSITA, Spitzer, Euclid, and JWST.
Abstract
Ultraluminous Ly
α
emitting galaxies (ULLAEs) with
erg s
−1
near the epoch of reionization (
z
> 5) make up the bright end of the LAE luminosity function (LF) and may provide insight into ...the process of reionization, including the formation of ionized bubbles around these extreme systems. We present a spectroscopic LF for ULLAEs at
z
= 5.7. We used data from the HEROES ∼45 deg
2
Subaru Hyper Suprime-Cam survey, which is centered on the North Ecliptic Pole and has both broadband (
grizY
) and narrowband (NB816 and NB921) imaging, to select candidate ULLAEs based on a NB816 excess and a strong broadband Lyman break. We spectroscopically observed 17 ULLAE candidates with DEIMOS on Keck II. We confirmed 12 as LAEs at
z
= 5.7, 9 of which are ULLAEs. The remaining sources are an active galactic nuclei at
z
= 5.7, an O
III
λ
5007 emitter at
z
= 0.63, a red star, and two spectroscopic nondetections. Using the nine confirmed ULLAEs, we construct a ULLAE LF at
z
= 5.7. After applying a comprehensive incompleteness correction, we compare our new
z
= 5.7 LF with our recent
z
= 6.6 LF and with other LFs from the literature to look for evolution at the ultraluminous end. We find the overall ratio of the
z
= 5.7 to
z
= 6.6 ULLAE comoving number densities to be
, which corresponds to an LF offset of
dex.
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