ABSTRACT
We report ALMA Band 9 continuum observations of the normal, dusty star-forming galaxy A1689-zD1 at z = 7.13, resulting in a ∼4.6 σ detection at 702 GHz. For the first time, these ...observations probe the far-infrared spectrum shortward of the emission peak of a galaxy in the Epoch of Reionization (EoR). Together with ancillary data from earlier works, we derive the dust temperature, Td, and mass, Md, of A1689-zD1 using both traditional modified blackbody spectral energy density fitting, and a new method that relies only on the C ii 158 μm line and underlying continuum data. The two methods give $T_{\rm d} = (42^{+13}_{-7}, 40^{+13}_{-7}$) K, and $M_{\rm d} = (1.7^{+1.3}_{-0.7}, 2.0^{+1.8}_{-1.0})\, \times {}\, 10^{7} \, \mathrm{ M}_{\odot }$. Band 9 observations improve the accuracy of the dust temperature (mass) estimate by ∼50 per cent (6 times). The derived temperatures confirm the reported increasing Td-redshift trend between z = 0 and 8; the dust mass is consistent with a supernova origin. Although A1689-zD1 is a normal UV-selected galaxy, our results, implying that ∼85 per cent of its star-formation rate is obscured, underline the non-negligible effects of dust in EoR galaxies.
Abstract
We present new ALMA observations and physical properties of a Lyman break galaxy at z = 7.15. Our target, B14-65666, has a bright ultra-violet (UV) absolute magnitude, MUV ≈ −22.4, and has ...been spectroscopically identified in Lyα with a small rest-frame equivalent width of ≈4 Å. A previous Hubble Space TElescope (HST) image has shown that the target is composed of two spatially separated clumps in the rest-frame UV. With ALMA, we have newly detected spatially resolved O iii 88 μm, C ii 158 μm, and their underlying dust continuum emission. In the whole system of B14-65666, the O iii and C ii lines have consistent redshifts of 7.1520 ± 0.0003, and the O iii luminosity, (34.4 ± 4.1) × 108 L⊙, is about three times higher than the C ii luminosity, (11.0 ± 1.4) × 108 L⊙. With our two continuum flux densities, the dust temperature is constrained to be Td ≈ 50–60 K under the assumption of a dust emissivity index of βd = 2.0–1.5, leading to a large total infrared luminosity of LTIR ≈ 1 × 1012 L⊙. Owing to our high spatial resolution data, we show that the O iii and C ii emission can be spatially decomposed into two clumps associated with the two rest-frame UV clumps whose spectra are kinematically separated by ≈200 km s−1. We also find these two clumps have comparable UV, infrared, O iii, and C ii luminosities. Based on these results, we argue that B14-65666 is a starburst galaxy induced by a major merger. The merger interpretation is also supported by the large specific star formation rate (defined as the star formation rate per unit stellar mass), sSFR $= 260^{+119}_{-57}\:$Gyr−1, inferred from our SED fitting. Probably, a strong UV radiation field caused by intense star formation contributes to its high dust temperature and the O iii-to-C ii luminosity ratio.
ABSTRACT
linestacker is a new open access and open source tool for stacking of spectral lines in interferometric data. linestacker is an ensemble of casa tasks, and can stack both 3D cubes or already ...extracted spectra. The algorithm is tested on increasingly complex simulated data sets, mimicking Atacama Large Millimeter/submillimeter Array, and Karl G. Jansky Very Large Array observations of C ii and CO(3–2) emission lines, from z ∼ 7 and z ∼ 4 galaxies, respectively. We find that the algorithm is very robust, successfully retrieving the input parameters of the stacked lines in all cases with an accuracy ≳90 per cent. However, we distinguish some specific situations showcasing the intrinsic limitations of the method. Mainly that high uncertainties on the redshifts (Δz > 0.01) can lead to poor signal-to-noise ratio improvement, due to lines being stacked on shifted central frequencies. Additionally, we give an extensive description of the embedded statistical tools included in linestacker: mainly bootstrapping, rebinning, and subsampling. Velocity rebinning is applied on the data before stacking and proves necessary when studying line profiles, in order to avoid artificial spectral features in the stack. Subsampling is useful to sort the stacked sources, allowing to find a subsample maximizing the searched parameters, while bootstrapping allows to detect inhomogeneities in the stacked sample. linestacker is a useful tool for extracting the most from spectral observations of various types.
ABSTRACT We present CO(1-0) observations obtained at the Karl G. Jansky Very Large Array for 14 galaxies with existing CO(3-2) measurements, including 11 galaxies that contain active galactic nuclei ...(AGNs) and three submillimeter galaxies (SMGs). We combine this sample with an additional 15 galaxies from the literature that have both CO(1-0) and CO(3-2) measurements in order to evaluate differences in CO excitation between SMGs and AGN host galaxies, to measure the effects of CO excitation on the derived molecular gas properties of these populations, and to look for correlations between the molecular gas excitation and other physical parameters. With our expanded sample of CO(3-2)/CO(1-0) line ratio measurements, we do not find a statistically significant difference in the mean line ratio between SMGs and AGN host galaxies as can be found in the literature; we instead find for AGN host galaxies and for SMGs (or for both populations combined). We also do not measure a statistically significant difference between the distributions of the line ratios for these populations at the p = 0.05 level, although this result is less robust. We find no excitation dependence on the index or offset of the integrated Schmidt-Kennicutt relation for the two CO lines, and we obtain indices consistent with N = 1 for the various subpopulations. However, including low-z "normal" galaxies increases our best-fit Schmidt-Kennicutt index to . While we do not reproduce correlations between the CO line width and luminosity, we do reproduce correlations between CO excitation and star-formation efficiency.
We report the results of a pilot study of CO(4 − 3) emission line of three Wide-field Infrared Survey Explorer (WISE)-selected hyper-luminous, dust-obscured quasars (QSOs) with sensitive ALMA Band 3 ...observations. These obscured QSOs with Lbol > 1014 L are among the most luminous objects in the universe. All three QSO hosts are clearly detected both in continuum and in CO(4 − 3) emission line. Based on CO(4 − 3) emission line detection, we derive the molecular gas masses (∼1010−11 M ), suggesting that these QSOs are gas-rich systems. We find that the obscured QSOs in our sample follow the similar relation as unobscured QSOs at high redshifts. We also find the complex velocity structures of CO(4 − 3) emission line, which provide the possible evidence for a gas-rich merger in W0149+2350 and possible molecular outflow in W0220+0137 and W0410−0913. Massive molecular outflow can blow away the obscured interstellar medium and make obscured QSOs evolve toward the UV/optical bright, unobscured phase. Our result is consistent with the popular active galactic nucleus (AGN) feedback scenario involving the co-evolution between the supermassive black holes and host galaxy.
Abstract
We present spatially resolved morphological properties of C
II
158
μ
m, O
III
88
μ
m, dust, and rest-frame ultraviolet (UV) continuum emission for A1689-zD1, a strongly lensed, sub-L* ...galaxy at
z
= 7.13, by utilizing deep Atacama Large Millimeter/submillimeter Array (ALMA) and Hubble Space Telescope (HST) observations. While the O
III
line and UV continuum are compact, the C
II
line is extended up to a radius of
r
∼ 12 kpc. Using multi-band rest-frame far-infrared continuum data ranging from 52 to 400
μ
m, we find an average dust temperature and emissivity index of
T
dust
=
41
−
14
+
17
K and
β
=
1.7
−
0.7
+
1.1
, respectively, across the galaxy. We find slight differences in the dust continuum profiles at different wavelengths, which may indicate that the dust temperature decreases with distance. We map the star formation rate (SFR) via IR and UV luminosities and determine a total SFR of 37 ± 1
M
⊙
yr
−1
with an obscured fraction of 87%. While the O
III
line is a good tracer of the SFR, the C
II
line shows deviation from the local
L
C
II
-SFR relations in the outskirts of the galaxy. Finally, we observe a clear difference in the line profile between C
II
and O
III
, with significant residuals (∼5
σ
) in the O
III
line spectrum after subtracting a single Gaussian model. This suggests a possible origin of the extended C
II
structure from the cooling of hot ionized outflows. The extended C
II
and high-velocity O
III
emission may both contribute in part to the high
L
O
III
/
L
C
II
ratios recently reported in
z
> 6 galaxies.
Abstract
The 2 mm Mapping Obscuration to Reionization with ALMA (MORA) Survey was designed to detect high-redshift (
z
≳ 4), massive, dusty star-forming galaxies (DSFGs). Here we present two likely ...high-redshift sources, identified in the survey, whose physical characteristics are consistent with a class of optical/near-infrared (OIR)-invisible DSFGs found elsewhere in the literature. We first perform a rigorous analysis of all available photometric data to fit spectral energy distributions and estimate redshifts before deriving physical properties based on our findings. Our results suggest the two galaxies, called MORA-5 and MORA-9, represent two extremes of the “OIR-dark” class of DSFGs. MORA-5 (
z
phot
=
4.3
−
1.3
+
1.5
) is a significantly more active starburst with a star formation rate (SFR) of
830
−
190
+
340
M
⊙
yr
−1
compared to MORA-9 (
z
phot
=
4.3
−
1.0
+
1.3
), whose SFR is a modest
200
−
60
+
250
M
⊙
yr
−1
. Based on the stellar masses (
M
⋆
≈ 10
10−11
M
⊙
), space density (
n
∼ (5 ± 2) × 10
−6
Mpc
−3
, which incorporates two other spectroscopically confirmed OIR-dark DSFGs in the MORA sample at
z
= 4.6 and
z
= 5.9), and gas depletion timescales (<1 Gyr) of these sources, we find evidence supporting the theory that OIR-dark DSFGs are the progenitors of recently discovered 3 <
z
< 4 massive quiescent galaxies.
ABSTRACT We utilize a Bayesian approach to fit the observed mid-IR-to-submillimeter/millimeter spectral energy distributions (SEDs) of 22 WISE-selected and submillimeter-detected, hyperluminous hot ...dust-obscured galaxies (Hot DOGs), with spectroscopic redshift ranging from 1.7 to 4.6. We compare the Bayesian evidence of a torus plusgraybody (Torus+GB) model with that of a torus-only (Torus) model and find that the Torus+GB model has higher Bayesian evidence for all 22 Hot DOGs than the torus-only model, which presents strong evidence in favor of the Torus+GB model. By adopting the Torus+GB model, we decompose the observed IR SEDs of Hot DOGs into torus and cold dust components. The main results are as follows. (1) Hot DOGs in our submillimeter-detected sample are hyperluminous ( ), with torus emission dominating the IR energy output. However, cold dust emission is non-negligible, contributing on average of total IR luminosity. (2) Compared to QSO and starburst SED templates, the median SED of Hot DOGs shows the highest luminosity ratio between mid-IR and submillimeter at rest frame, while it is very similar to that of QSOs at , suggesting that the heating sources of Hot DOGs should be buried AGNs. (3) Hot DOGs have high dust temperatures ( K) and high IR luminosity of cold dust. The relation of Hot DOGs suggests that the increase in IR luminosity for Hot DOGs is mostly due to the increase of the dust temperature, rather than dust mass. Hot DOGs have lower dust masses than submillimeter galaxies (SMGs) and QSOs within a similar redshift range. Both high IR luminosity of cold dust and relatively low dust mass in Hot DOGs can be expected by their relatively high dust temperatures. (4) Hot DOGs have high dust-covering factors (CFs), which deviate from the previously proposed trend of the dust CF decreasing with increasing bolometric luminosity. Finally, we can reproduce the observed properties in Hot DOGs by employing a physical model of galaxy evolution. This result suggests that Hot DOGs may lie at or close to peaks of both star formation and black hole growth histories, and represent a transit phase during the evolutions of massive galaxies, transforming them from the dusty starburst-dominated phase to the optically bright QSO phase.
The far-infrared fine-structure line C ii at 1900.5 GHz is known to be one of the brightest cooling lines in local galaxies, and therefore it has been suggested to be an efficient tracer for star ...formation in very high redshift galaxies. However, recent results for galaxies at z > 6 have yielded numerous non-detections in star-forming galaxies, except for quasars and submillimetre galaxies. We report the results of ALMA observations of two lensed, star-forming galaxies at z = 6.029 and z = 6.703. The galaxy A383-5.1 (star formation rate SFR of 3.2 M⊙ yr−1 and magnification of μ = 11.4 ± 1.9) shows a line detection with $L_{\rm C\,\small {II}} = 8.9\times 10^{6}$ L⊙, making it the lowest $L_{\rm C\,\small {II}}$ detection at z > 6. For MS0451-H (SFR = 0.4 M⊙ yr−1 and μ = 100 ± 20) we provide an upper limit of $L_{\rm C\,\small {II}} < 3\times 10^{5}$ L⊙, which is 1 dex below the local SFR–$L_{\rm C\,\small {II}}$ relations. The results are consistent with predictions for low-metallicity galaxies at z > 6; however, other effects could also play a role in terms of decreasing LCII. The detection of A383-5.1 is encouraging and suggests that detections are possible, but much fainter than initially predicted.
A merger in the dusty, z = 7.5 galaxy A1689-zD1? Knudsen, Kirsten K; Watson, Darach; Frayer, David ...
Monthly notices of the Royal Astronomical Society,
04/2017, Volume:
466, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract
The gravitationally lensed galaxy A1689-zD1 is one of the most distant spectroscopically confirmed sources (z = 7.5). It is the earliest known galaxy where the interstellar medium (ISM) has ...been detected; dust emission was detected with the Atacama Large Millimetre Array (ALMA). A1689-zD1 is also unusual among high-redshift dust emitters as it is a sub-L
★ galaxy and is therefore a good prospect for the detection of gaseous ISM in a more typical galaxy at this redshift. We observed A1689-zD1 with ALMA in bands 6 and 7 and with the Green Bank Telescope (GBT) in band Q. To study the structure of A1689-zD1, we map the mm-thermal dust emission and find two spatial components with sizes about 0.4 − 1.7 kpc (lensing-corrected). The rough spatial morphology is similar to what is observed in the near-infrared with HST and points to a perturbed dynamical state, perhaps indicative of a major merger or a disc in early formation. The ALMA photometry is used to constrain the far-infrared spectral energy distribution, yielding a dust temperature (T
dust ∼ 35–45 K for β = 1.5 − 2). We do not detect the CO(3-2) line in the GBT data with a 95 per cent upper limit of 0.3 mJy observed. We find a slight excess emission in ALMA band 6 at 220.9 GHz. If this excess is real, it is likely due to emission from the C ii 158.8 μm line at
$z_{\rm C\,\small {II}} = 7.603$
. The stringent upper limits on the C ii L
FIR luminosity ratio suggest a C ii deficit similar to several bright quasars and massive starbursts.
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![[C ii] emission in z ∼ 6 st...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1745-3925/small "[C ii] emission in z ∼ 6 strongly lensed, star-forming galaxies")