We present a physical characterization of MM J100026.36+021527.9 (a.k.a. "Mambo-9"), a dusty star-forming galaxy (DSFG) at z = 5.850 0.001. This is the highest-redshift unlensed DSFG (and fourth most ...distant overall) found to date and is the first source identified in a new 2 mm blank-field map in the COSMOS field. Though identified in prior samples of DSFGs at 850 m to 1.2 mm with unknown redshift, the detection at 2 mm prompted further follow-up as it indicated a much higher probability that the source was likely to sit at z > 4. Deep observations from the Atacama Large Millimeter and submillimeter Array (ALMA) presented here confirm the redshift through the secure detection of 12CO(J = 6→5) and p-H2O (21,1 → 20,2). Mambo-9 is composed of a pair of galaxies separated by 6 kpc with corresponding star formation rates of 590 M yr−1 and 220 M yr−1, total molecular hydrogen gas mass of (1.7 0.4) × 1011M , dust mass of (1.3 0.3) × 109M , and stellar mass of ( ) × 109M . The total halo mass, (3.3 0.8) × 1012M , is predicted to exceed 1015M by z = 0. The system is undergoing a merger-driven starburst that will increase the stellar mass of the system tenfold in τdepl = 40−80 Myr, converting its large molecular gas reservoir (gas fraction of ) into stars. Mambo-9 evaded firm spectroscopic identification for a decade, following a pattern that has emerged for some of the highest-redshift DSFGs found. And yet, the systematic identification of unlensed DSFGs like Mambo-9 is key to measuring the global contribution of obscured star formation to the star formation rate density at z 4, the formation of the first massive galaxies, and the formation of interstellar dust at early times ( 1 Gyr).
We present 16 new ultrabright HAB 25 galaxy candidates at z ∼ 8 identified over the COSMOS/UltraVISTA field. The new search takes advantage of the deepest-available ground-based optical and ...near-infrared observations, including the DR3 release of UltraVISTA and full-depth Spitzer/IRAC observations from the SMUVS and SPLASH programs. Candidates are selected using Lyman-break color criteria, combined with strict optical non-detection and SED-fitting criteria, designed to minimize contamination by low-redshift galaxies and low-mass stars. HST/WFC3 coverage from the DASH program reveals that one source evident in our ground-based near-IR data has significant substructure and may actually correspond to 3 separate z ∼ 8 objects, resulting in a total sample of 18 galaxies, 10 of which seem to be fairly robust (with a >97% probability of being at z > 7). The UV-continuum slope β for the bright z ∼ 8 sample is β = −2.2 0.6, bluer but still consistent with that of similarly bright galaxies at z ∼ 6 (β = −1.55 0.17) and z ∼ 7 (β = −1.75 0.18). Their typical stellar masses are M , with the SFRs of yr−1, specific SFR of Gyr−1, stellar ages of Myr, and low dust content mag. Using this sample we constrain the bright end of the z ∼ 8 UV luminosity function. When combined with recent empty field luminosity function estimates at similar redshifts, the resulting z ∼ 8 luminosity function can be equally well represented by either a Schechter or a double-power-law form. Assuming a Schechter parameterization, the best-fit characteristic magnitude is mag with a very steep faint-end slope . These new candidates include some of the brightest objects found at these redshifts, 0.5-1.0 magnitude brighter than those found over CANDELS, and providing excellent targets for spectroscopic and longer-wavelength follow-up studies.
Abstract
Until now, our knowledge of the extragalactic universe at mid-infrared (mid-IR) wavelengths (>5
μ
m) was limited to rare active galactic nuclei and the brightest normal galaxies up to
z
∼ 3. ...The advent of JWST with its Mid-Infrared Instrument (MIRI) will revolutionize the ability of the mid-IR regime as a key wavelength domain to probe the high-
z
universe. In this work we present a first study of JWST MIRI 7.7
μ
m sources selected with >3
σ
significance from the lensing cluster field SMACS J0723.3-7327. We model their spectral energy distribution (SED) fitting with 13 JWST and Hubble Space Telescope broad bands, in order to obtain photometric redshifts and derived physical parameters for all these sources. We find that this 7.7
μ
m galaxy sample is mainly composed of normal galaxies up to
z
= 4 and has a tail of about 2% of sources at higher redshifts to
z
≈ 9–10. The vast majority of our galaxies have 3.6–7.7 < 0 colors and very few of them need high dust extinction values (
A
V
= 3–6 mag) for their SED fitting. The resulting lensing-corrected stellar masses span the range 10
7
–10
11
M
⊙
. Overall, our results clearly show that the first MIRI 7.7
μ
m observations of deep fields are already useful to probe the high-redshift universe and suggest that the deeper 7.7
μ
m observations to be available very soon will open up, for the first time, the epoch of reionization at mid-IR wavelengths.
Abstract
Submillimeter observations reveal the star formation activity obscured by dust in the young Universe. It still remains unclear how galaxies detected at submillimeter wavelengths are related ...to ultraviolet/optical-selected galaxies in terms of their observed quantities, physical properties, and evolutionary stages. Deep near- and mid-infrared observational data are crucial to characterize the stellar properties of galaxies detected with submillimeter emission. In this study, we make use of a galaxy catalog from the Spitzer Matching survey of the UltraVISTA ultra-deep Stripes. By crossmatching with a submillimeter source catalog constructed with archival data of the Atacama Large Millimeter/submillimeter Array (ALMA), we search for galaxies at
z
> 2 with a submillimeter detection in our galaxy catalog. We find that the ALMA-detected galaxies at
z
> 2 are systematically massive and have redder
K
s
–4.5 colors than the nondetected galaxies. The redder colors are consistent with the larger dust reddening values of the ALMA-detected galaxies obtained from spectral energy distribution (SED) fitting. We also find that the ALMA-detected galaxies tend to have brighter 4.5
μ
m magnitudes. This may suggest that they tend to have smaller mass-to-light ratios and thus to be younger than star-forming galaxies fainter at submillimeter wavelengths with similar stellar masses. We identify starburst galaxies with high specific star formation rates among both ALMA-detected and nondetected SMUVS sources. Irrespective of their brightness at submillimeter wavelengths, these populations have similar dust reddening values, which may suggest a variety of dust SED shapes among the starburst galaxies at
z
> 2.
Abstract
We present the characteristics of 2 mm selected sources from the largest Atacama Large Millimeter/submillimeter Array (ALMA) blank-field contiguous survey conducted to date, the Mapping ...Obscuration to Reionization with ALMA (MORA) survey covering 184 arcmin
2
at 2 mm. Twelve of 13 detections above 5
σ
are attributed to emission from galaxies, 11 of which are dominated by cold dust emission. These sources have a median redshift of
〈
z
2
mm
〉
=
3.6
−
0.3
+
0.4
primarily based on optical/near-infrared photometric redshifts with some spectroscopic redshifts, with 77% ± 11% of sources at
z
> 3 and 38% ± 12% of sources at
z
> 4. This implies that 2 mm selection is an efficient method for identifying the highest-redshift dusty star-forming galaxies (DSFGs). Lower-redshift DSFGs (
z
< 3) are far more numerous than those at
z
> 3 yet are likely to drop out at 2 mm. MORA shows that DSFGs with star formation rates in excess of 300
M
⊙
yr
−1
and a relative rarity of ∼10
−5
Mpc
−3
contribute ∼30% to the integrated star formation rate density at 3 <
z
< 6. The volume density of 2 mm selected DSFGs is consistent with predictions from some cosmological simulations and is similar to the volume density of their hypothesized descendants: massive, quiescent galaxies at
z
> 2. Analysis of MORA sources’ spectral energy distributions hint at steeper empirically measured dust emissivity indices than reported in typical literature studies, with
〈
β
〉
=
2.2
−
0.4
+
0.5
. The MORA survey represents an important step in taking census of obscured star formation in the universe’s first few billion years, but larger area 2 mm surveys are needed to more fully characterize this rare population and push to the detection of the universe’s first dusty galaxies.
Abstract
Recent controversy regarding the existence of massive (
log
(
M
*
/
M
⊙
)
≳
11
) galaxies at
z
> 6 poses a challenge for galaxy formation theories. Hence, it is of critical importance to ...understand the effects of SED fitting methods on stellar mass estimates of Epoch of Reionization galaxies. In this work, we perform a case study on the AGN host galaxy candidate COS-87259, with spectroscopic redshift
z
spec
= 6.853, that is claimed to have an extremely high stellar mass of
log
(
M
*
/
M
⊙
)
∼
11.2
. We test a suite of different SED fitting algorithms and stellar population models on our independently measured photometry in 17 broad bands for this source. Between five different code setups, the stellar mass estimates for COS-87259 span
log
(
M
*
/
M
⊙
)
=
10.24
–11.00, while the reduced
χ
2
values of the fits are all close to unity within
Δ
χ
ν
2
=
1.2
, such that the quality of the SED fits is basically indistinguishable. Only when we adopt a nonparametric star formation history model within
Prospector
do we retrieve a stellar mass exceeding
log
(
M
*
/
M
⊙
)
=
11
. Although the derived stellar masses change when using previously reported photometry for this source, the nonparametric SED-fitting method always yields the highest values. As these models are becoming increasingly popular for James Webb Space Telescope high-redshift science, we stress the absolute importance of testing various SED fitting routines particularly on apparently very massive galaxies at such high redshifts.
Abstract
We analyze a sample of 3300 galaxies between redshifts
z
≃ 3.5 and
z
≃ 8.5 selected from James Webb Space Telescope (JWST) images in the Hubble Ultra Deep Field and UKIDSS Ultra Deep Survey ...field, including objects with stellar masses as low as ≃10
8
M
⊙
up to
z
≃ 8. The depth and wavelength coverage of the JWST data allows us, for the first time, to derive robust stellar masses for such high-
z
, low stellar mass galaxies on an individual basis. We compute the galaxy stellar mass function, after complementing our sample with ancillary data from CANDELS to constrain the GMSF at high stellar masses (
M
>
M
*
). Our results show a steepening of the low stellar mass end slope (
α
) with redshift, with
α
= −1.61 ± 0.05 at
z
≃ 4 and
α
= −1.98 ± 0.14 at
z
≃ 7. We also observe an evolution of the normalization
ϕ
*
from
z
≃ 7 to
z
≃ 4, with
ϕ
z
≃
4
*
/
ϕ
z
≃
7
*
=
130
−
50
+
210
. Our study incorporates a novel method for the estimation of the Eddington bias, which takes into account its possible dependence both on stellar mass and redshift, while allowing for skewness in the error distribution. We finally compute the resulting cosmic stellar mass density and find a flatter evolution with redshift than previous studies.
This paper describes new deep 3.6 and 4.5 m imaging of three UltraVISTA near-infrared survey stripes within the COSMOS field. The observations were carried out with Spitzer's Infrared Array Camera ...(IRAC) for the Spitzer Matching Survey of the UltraVISTA Deep Stripes (SMUVS). In this work we present our data reduction techniques, and document the resulting mosaics, coverage maps, and catalogs in both IRAC passbands for the three easternmost UltraVISTA survey stripes, covering a combined area of about 0.66 deg2, of which 0.45 deg2 have at least 20 hr of integration time. SMUVS reaches point-source sensitivities of about 25.0 AB mag (0.13 Jy) at both 3.6 and 4.5 m, with a significance of 4 , accounting for both survey sensitivity and source confusion. To this limit the SMUVS catalogs contain a total of ∼350,000 sources, each of which is detected significantly in at least one IRAC band. Because of its uniform and high sensitivity, relatively large area coverage, and the wide array of ancillary data available in COSMOS, the SMUVS survey will be useful for a large number of cosmological investigations. We make all images and catalogs described herein publicly available via the Spitzer Science Center.
Abstract
Using the novel James Webb Space Telescope (JWST)/NIRCam observations in the A2744 field, we present a first spatially resolved overview of a Hubble Space Telescope (HST)-dark galaxy, ...spectroscopically confirmed at
z
= 2.58 with magnification
μ
≈ 1.9. While being largely invisible at ∼1
μ
m with NIRCam, except for sparse clumpy substructures, the object is well detected and resolved in the long-wavelength bands with a spiral shape clearly visible in F277W. By combining ancillary Atacama Large Millimeter/submillimeter Array (ALMA) and Herschel data, we infer that this object is an edge-on dusty spiral with an intrinsic stellar mass log (
M
*
/
M
⊙
) ∼ 11.3 and a dust-obscured star formation rate ∼300
M
⊙
yr
−1
. A massive quiescent galaxy (log (
M
*
/
M
⊙
) ∼ 10.8) with tidal features lies 2.″0 away (
r
∼ 9 kpc), at a consistent redshift as inferred by JWST photometry, indicating a potential major merger. The dusty spiral lies on the main sequence of star formation, and shows high dust attenuation in the optical (3 <
A
V
< 4.5). In the far-infrared, its integrated dust spectral energy distribution is optically thick up to
λ
0
∼ 500
μ
m, further supporting the extremely dusty nature. Spatially resolved analysis of the HST-dark galaxy reveals a largely uniform
A
V
∼ 4 area spanning ∼57 kpc
2
, which spatially matches to the ALMA 1 mm continuum emission. Accounting for the surface brightness dimming and the depths of current JWST surveys, unlensed analogs of the HST-dark galaxy at
z
> 4 would be only detectable in F356W and F444W in an UNCOVER-like survey, and become totally JWST-dark at
z
∼ 6. This suggests that detecting highly attenuated galaxies in the Epoch of Reionization might be a challenging task for JWST.
We report on the discovery of three especially bright candidate galaxies. Five sources were targeted for follow-up with the Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3), selected from a ...larger sample of 16 bright ( mag) candidate Lyman break galaxies (LBGs) identified over 1.6 degrees2 of the COSMOS/UltraVISTA field. These were selected as Y and J dropouts by leveraging the deep (Y-to- mag, ) NIR data from the UltraVISTA DR3 release, deep ground-based optical imaging from the CFHTLS and Suprime-Cam programs, and Spitzer/IRAC mosaics combining observations from the SMUVS and SPLASH programs. Through the refined spectral energy distributions, which now also include new HyperSuprimeCam g-, r-, i-, z-, and Y-band data, we confirm that 3/5 galaxies have robust , consistent with the initial selection. The remaining 2/5 galaxies have a nominal . However, with HST data alone, these objects have increased probability of being at . We measure mean UV continuum slopes for the three galaxies, marginally bluer than similarly luminous in CANDELS but consistent with previous measurements of similarly luminous galaxies at . The circularized effective radius for our brightest source is 0.9 0.3 kpc, similar to previous measurements for a bright galaxy and bright galaxies. Finally, enlarging our sample to include the six brightest LBGs identified over UltraVISTA (i.e., including three other sources from Labbé et al.) we estimate for the first time the volume density of galaxies at the extreme bright end ( mag) of the UV luminosity function. Despite this exceptional result, the still large statistical uncertainties do not allow us to discriminate between a Schechter and a double-power-law form.
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