Until recently, determining the rotational properties of galaxies in the early universe ( , universe age Gyr) was impractical, with the exception of a few strongly lensed systems. Combining the high ...resolution and sensitivity of ALMA at (sub-)millimeter wavelengths with the typically high strength of the C ii 158 m emission line from galaxies and long-developed dynamical modeling tools raises the possibility of characterizing the gas dynamics in both extreme starburst galaxies and normal star-forming disk galaxies at . Using a procedure centered around GIPSY's rotcur task, we have fit tilted ring models to some of the best available ALMA C ii data of a small set of galaxies: the MS galaxies HZ9 and HZ10, the damped Ly absorber host galaxy ALMA J0817+1351, the submm galaxies AzTEC/C159 and COSMOS J1000+0234, and the quasar host galaxy ULAS J1319+0950. This procedure directly derives rotation curves and dynamical masses as functions of radius for each object. In one case, we present evidence for a dark matter halo of . We present an analysis of the possible velocity dispersions of two sources based on matching simulated observations to the integrated C ii line profiles. Finally, we test the effects of observation resolution and sensitivity on our results. While the conclusions remain limited at the resolution and signal-to-noise ratios of these observations, the results demonstrate the viability of the modeling tools at high redshift, and the exciting potential for detailed dynamical analysis of the earliest galaxies, as ALMA achieves full observational capabilities.
ABSTRACT We present an analysis of a deep (1 = 13 Jy) cosmological 1.2 mm continuum map based on ASPECS, the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field. In the 1 arcmin2 covered by ...ASPECS we detect nine sources at significance at 1.2 mm. Our ALMA-selected sample has a median redshift of , with only one galaxy detected at z > 2 within the survey area. This value is significantly lower than that found in millimeter samples selected at a higher flux density cutoff and similar frequencies. Most galaxies have specific star formation rates (SFRs) similar to that of main-sequence galaxies at the same epoch, and we find median values of stellar mass and SFRs of and yr−1, respectively. Using the dust emission as a tracer for the interstellar medium (ISM) mass, we derive depletion times that are typically longer than 300 Myr, and we find molecular gas fractions ranging from ∼0.1 to 1.0. As noted by previous studies, these values are lower than those using CO-based ISM estimates by a factor of ∼2. The 1 mm number counts (corrected for fidelity and completeness) are in agreement with previous studies that were typically restricted to brighter sources. With our individual detections only, we recover 55% 4% of the extragalactic background light (EBL) at 1.2 mm measured by the Planck satellite, and we recover 80% 7% of this EBL if we include the bright end of the number counts and additional detections from stacking. The stacked contribution is dominated by galaxies at , with stellar masses of (1-3) × 1010 M . For the first time, we are able to characterize the population of galaxies that dominate the EBL at 1.2 mm.
We explore the properties of the submillijansky radio population at 20 cm by applying a newly developed optical color-based method to separate star- forming (SF) from active galactic nucleus (AGN) ...galaxies at intermediate redshifts. Although optical rest-frame colors are used, our separation method is shown to be efficient and not biased against dusty starburst galaxies. This classification method has been calibrated and tested on a local radio- selected optical sample. Given accurate multiband photometry and redshifts, it carries the potential to be generally applicable to any galaxy sample where SF and AGN galaxies are the two dominant populations. In order to quantify the properties of the submillijansky radio population, we have analyzed image2,400 radio sources, detected at 20 cm in the VLA-COSMOS survey; 90% of these have submillijansky flux densities. We classify the objects into (1) star candidates, (2) quasi-stellar objects, (3) AGN, (4) SF, and (5) high-redshift galaxies. We find, for the composition of the submillijansky radio population, that SF galaxies are not the dominant population at submillijansky flux levels, as previously often assumed, but that they make up an approximately constant fraction of 30%-40% in the flux density range of image50 muJy to 0.7 mJy. In summary, based on the entire VLA-COSMOS radio population at 20 cm, we find that the radio population at these flux densities is a mixture of roughly 30%-40% of SF and 50%-60% of AGN galaxies, with a minor contribution (image10%) of QSOs.
We present Atacama Large Millimeter/submillimeter Array observations of the dust continuum and C ii 158 m line emission from the z = 6.0695 Lyman-Break Galaxy (LBG) WMH5. These observations at 0 3 ...spatial resolution show a compact (∼3 kpc) main galaxy in dust and C ii emission, with a "tail" of emission extending to the east by about 5 kpc (in projection). The C ii tail is comprised predominantly of two distinct sub-components in velocity, separated from the core by ∼100 and 250 km s−1, with narrow intrinsic widths of about 80 km s−1, which we call "sub-galaxies." The sub-galaxies themselves are extended east-west by about 3 kpc in individual channel images. The C ii tail joins smoothly into the main galaxy velocity field. The C ii line to continuum ratios are comparable for the main and sub-galaxy positions, within a factor two. In addition, these ratios are comparable to LBGs. We conjecture that the WMH5 system represents the early formation of a galaxy through the accretion of smaller satellite galaxies, embedded in a smoother gas distribution, along a possibly filamentary structure. The results are consistent with current cosmological simulations of early galaxy formation and support the idea of very early enrichment with dust and heavy elements of the accreting material.
ABSTRACT We present a search for C ii line and dust continuum emission from optical dropout galaxies at z > 6 using ASPECS, our Atacama Large Millimeter submillimeter Array Spectroscopic Survey in ...the Hubble Ultra-deep Field (UDF). Our observations, which cover the frequency range of 212-272 GHz, encompass approximately the range of 6 < z < 8 for C ii line emission and reach a limiting luminosity of LC ii ∼ (1.6-2.5) × 108 L . We identify 14 C ii line emitting candidates in this redshift range with significances >4.5 , two of which correspond to blind detections with no optical counterparts. At this significance level, our statistical analysis shows that about 60% of our candidates are expected to be spurious. For one of our blindly selected C ii line candidates, we tentatively detect the CO(6-5) line in our parallel 3 mm line scan. None of the line candidates are individually detected in the 1.2 mm continuum. A stack of all C ii candidates results in a tentative detection with S1.2 mm = 14 5 Jy. This implies a dust-obscured star-formation rate (SFR) of (3 1) M yr−1. We find that the two highest-SFR objects have candidate C ii lines with luminosities that are consistent with the low-redshift LC ii versus SFR relation. The other candidates have significantly higher C ii luminosities than expected from their UV-based SFR. At the current sensitivity, it is unclear whether the majority of these sources are intrinsically bright C ii emitters, or spurious sources. If only one of our line candidates was real (a scenario greatly favored by our statistical analysis), we find a source density for C ii emitters at 6 < z < 8 that is significantly higher than predicted by current models and some extrapolations from galaxies in the local universe.
In the context of the VLA-COSMOS Deep project, additional VLA A array observations at 1.4 GHz were obtained for the central degree of the COSMOS field and combined with the existing data from the ...VLA-COSMOS Large project. A newly constructed Deep mosaic with a resolution of 2.''5 was used to search for sources down to 4{sigma} with 1{sigma} {approx} 12 {mu}Jy beam{sup -1} in the central 50' x 50'. This new catalog is combined with the catalog from the Large project (obtained at 1.''5 x 1.''4 resolution) to construct a new Joint catalog. All sources listed in the new Joint catalog have peak flux densities of {>=}5{sigma} at 1.''5 and/or 2.''5 resolution to account for the fact that a significant fraction of sources at these low flux levels are expected to be slightly resolved at 1.''5 resolution. All properties listed in the Joint catalog, such as peak flux density, integrated flux density, and source size, are determined in the 2.''5 resolution Deep image. In addition, the Joint catalog contains 43 newly identified multi-component sources.
We report the appearance of a new radio source at a projected offset of 460 pc from the nucleus of Cygnus A. The flux density of the source (which we designate Cygnus A-2) rose from an upper limit of ...<0.5 mJy in 1989 to 4 mJy in 2016 ( = 8.5 GHz), but is currently not varying by more than a few percent per year. The radio luminosity of the source is comparable to the most luminous known supernovae, it is compact in Very Long Baseline Array observations down to a scale of 4 pc, and it is coincident with a near-infrared point source seen in pre-existing adaptive optics and HST observations. The most likely interpretation of this source is that it represents a secondary supermassive black hole in a close orbit around the Cygnus A primary, though an exotic supernova model cannot be ruled out. The gravitational influence of a secondary SMBH at this location may have played an important role in triggering the rapid accretion that has powered the Cygnus A radio jet over the past 107 years.
Abstract
We report the observation by the Atacama Large Millimeter/submillimeter Array (ALMA) of a
z
≳ 10 galaxy candidate (GHZ1) discovered from the GLASS–JWST Early Release Science Program. Our ...ALMA program aims to detect the O
iii
emission line at the rest-frame frequency 3393.0062 GHz (88.36
μ
m) and far-IR continuum emission with the spectral window setup seamlessly covering a 26.125 GHz frequency range (10.10 <
z
< 11.14). A total of 7 hr of on-source integration was employed, using four frequency settings to cover the full range (1.7 hr per setting), with 0.″7 angular resolution. No line or continuum is clearly detected, with 5
σ
upper limits on the line emission of 0.93 mJy beam
−1
at 25 km s
−1
channel
−1
and on the continuum emission of 30
μ
Jy beam
−1
. We report marginal spectral (at 225 km s
−1
resolution) and continuum features (4.1
σ
and 2.6
σ
peak signal-to-noise ratio, respectively), within 0.″17 from the JWST position of GHZ1. This spectral feature implies
z
= 10.38 and needs to be verified with further observations. Assuming that the best estimate of photometric redshift (
z
=
10.60
−
0.60
+
0.52
) is correct, the model of the galaxy’s broadband spectral energy distribution for the 3
σ
upper limit of the continuum flux from GHZ1 suggests that GHZ1 has a small amount of dust (
M
d
≲ 10
4
M
⊙
) at a high temperature (
T
d
≳ 90 K). The 5
σ
upper limit on the O
iii
88
μ
m
line luminosity and the inferred star formation rate of GHZ1 are consistent with the properties of low-metallicity dwarf galaxies. We also report serendipitous clear detections of six continuum sources at the locations of the JWST galaxy counterparts in the field.
We present Karl G. Jansky Very Large Array observations of the CO(2-1) emission in the z = 4.05 submillimeter galaxy (SMG) GN20. These high-resolution data allow us to image the molecular gas at 1.3 ...kpc resolution just 1.6 Gyr after the big bang. The data reveal a clumpy, extended gas reservoir, 14 + or - 4 kpc in diameter, in unprecedented detail. A dynamical analysis shows that the data are consistent with a rotating disk of total dynamical mass 5.4 + or - 2.4 x 10 super(11) M sub(middot in circle). We use this dynamical mass estimate to constrain the CO-to-H sub(2) mass conversion factor ( alpha sub(CO)), finding alpha sub(CO) = 1.1 + or - 0.6 M sub(middot in circle)(K km s super(-1) pc super(2)) super(-1). We identify five distinct molecular gas clumps in the disk of GN20 with masses a few percent of the total gas mass, brightness temperatures of 16-31K, and surface densities of >3200-4500 x ( alpha CO/0.8) M sub(middot in circle) pc super(-2). Virial mass estimates indicate they could be self-gravitating, and we constrain their CO-to-H sub(2) mass conversion factor to be <0.2-0.7 M sub(middot in circle)(K km s super(-1) pc super(2)) super(-1). A multiwavelength comparison demonstrates that the molecular gas is concentrated in a region of the galaxy that is heavily obscured in the rest-frame UV/optical. We investigate the spatially resolved gas excitation and find that the CO(6-5)/CO(2-1) ratio is constant with radius, consistent with star formation occurring over a large portion of the disk. We discuss the implications of our results in the context of different fueling scenarios for SMGs.
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