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.
We present a list of candidate gravitationally lensed dusty star-forming galaxies (DSFGs) from the HerMES Large Mode Survey and the Herschel Stripe 82 Survey. Together, these partially overlapping ...surveys cover 372 deg super(2) on the sky. After removing local spiral galaxies and known radio-loud blazars, our candidate list of lensed DSFGs is composed of 77 sources with 500 mum flux densities (S sub(500)) greater than 100 mJy. Such sources are dusty starburst galaxies similar to the first bright sub-millimeter galaxies (SMGs) discovered with SCUBA. We expect a large fraction of this list to be strongly lensed, with a small fraction made up of bright SMG-SMG mergers that appear as hyper-luminous infrared galaxies (L sub(IR)> 10 super(13)L sub(middot in circle)). Thirteen of the 77 candidates have spectroscopic redshifts from CO spectroscopy with ground-based interferometers, putting them at z> 1 and well above the redshift of the foreground lensing galaxies. The surface density of our sample is 0.21 + or - 0.03 deg super(-2). We present follow-up imaging of a few of the candidates to confirm their lensing nature. The sample presented here is an ideal tool for higher-resolution imaging and spectroscopic observations to understand the detailed properties of starburst phenomena in distant galaxies.
Dust-enshrouded, starbursting, submillimeter galaxies (SMGs) at z ≥ 3 have been proposed as progenitors of z ≥ 2 compact quiescent galaxies (cQGs). To test this connection, we present a detailed ...spatially resolved study of the stars, dust, and stellar mass in a sample of six submillimeter-bright starburst galaxies at z ∼ 4.5. The stellar UV emission probed by HST is extended and irregular and shows evidence of multiple components. Informed by HST, we deblend Spitzer/IRAC data at rest-frame optical, finding that the systems are undergoing minor mergers with a typical stellar mass ratio of 1:6.5. The FIR dust continuum emission traced by ALMA locates the bulk of star formation in extremely compact regions (median re = 0.70 0.29 kpc), and it is in all cases associated with the most massive component of the mergers (median ). We compare spatially resolved UV slope (β) maps with the FIR dust continuum to study the infrared excess (IRX = LIR/LUV)-β relation. The SMGs display systematically higher IRX values than expected from the nominal trend, demonstrating that the FIR and UV emissions are spatially disconnected. Finally, we show that the SMGs fall on the mass-size plane at smaller stellar masses and sizes than the cQGs at z = 2. Taking into account the expected evolution in stellar mass and size between z = 4.5 and z = 2 due to the ongoing starburst and mergers with minor companions, this is in agreement with a direct evolutionary connection between the two populations.
Selecting sources with rising flux densities towards longer wavelengths from Herschel/Spectral and Photometric Imaging Receiver (SPIRE) maps is an efficient way to produce a catalogue rich in ...high-redshift (z > 4) dusty star-forming galaxies. The effectiveness of this approach has already been confirmed by spectroscopic follow-up observations, but the previously available catalogues made this way are limited by small survey areas. Here we apply a map-based search method to 274 deg2 of the Herschel Multi-tiered Extragalactic Survey (HerMES) Large Mode Survey and create a catalogue of 477 objects with SPIRE flux densities S
500 > S
350 > S
250 and a 5σ cut-off S
500 > 52 mJy. From this catalogue we determine that the total number of these ‘red’ sources is at least an order of magnitude higher than predicted by galaxy evolution models. These results are in agreement with previous findings in smaller HerMES fields; however, due to our significantly larger sample size we are also able to investigate the shape of the red source counts for the first time. We have obtained spectroscopic redshift measurements for two of our sources using the Atacama Large Millimeter/submillimeter Array. The redshifts z = 5.1 and 3.8 confirm that with our selection method we can indeed find high-redshift dusty star-forming galaxies.
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.
We present detections of the CO(J = 1–0) emission line in a sample of four massive star-forming galaxies at z ∼ 1.5–2.2 obtained with the Karl G. Jansky Very Large Array. Combining these observations ...with previous CO(2–1) and CO(3–2) detections of these galaxies, we study the excitation properties of the molecular gas in our sample sources. We find an average line brightness temperature ratios of R
21 = 0.70 ± 0.16 and R
31 = 0.50 ± 0.29, based on measurements for three and two galaxies, respectively. These results provide additional support to previous indications of sub-thermal gas excitation for the CO(3–2) line with a typically assumed line ratio R
31 ∼ 0.5. For one of our targets, BzK-21000, we present spatially resolved CO line maps. At the resolution of 0.18 arcsec (1.5 kpc), most of the emission is resolved out except for some clumpy structure. From this, we attempt to identify molecular gas clumps in the data cube, finding four possible candidates. We estimate that <40 per cent of the molecular gas is confined to giant clumps (∼1.5 kpc in size), and thus most of the gas could be distributed in small fainter clouds or in fairly diffuse extended regions of lower brightness temperatures than our sensitivity limit.
Stellar archaeology shows that massive elliptical galaxies formed rapidly about ten billion years ago with star-formation rates of above several hundred solar masses per year. Their progenitors are ...probably the submillimetre bright galaxies at redshifts z greater than 2. Although the mean molecular gas mass (5 × 10(10) solar masses) of the submillimetre bright galaxies can explain the formation of typical elliptical galaxies, it is inadequate to form elliptical galaxies that already have stellar masses above 2 × 10(11) solar masses at z ≈ 2. Here we report multi-wavelength high-resolution observations of a rare merger of two massive submillimetre bright galaxies at z = 2.3. The system is seen to be forming stars at a rate of 2,000 solar masses per year. The star-formation efficiency is an order of magnitude greater than that of normal galaxies, so the gas reservoir will be exhausted and star formation will be quenched in only around 200 million years. At a projected separation of 19 kiloparsecs, the two massive starbursts are about to merge and form a passive elliptical galaxy with a stellar mass of about 4 × 10(11) solar masses. We conclude that gas-rich major galaxy mergers with intense star formation can form the most massive elliptical galaxies by z ≈ 1.5.
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ALMA suggests outflows in z ∼ 5.5 galaxies Gallerani, S; Pallottini, A; Feruglio, C ...
Monthly notices of the Royal Astronomical Society,
2018, Volume:
473, Issue:
2
Journal Article
Peer reviewed
Open access
Abstract
We present the first attempt to detect outflows from galaxies approaching the Epoch of Reionization (EoR) using a sample of nine star-forming (SFR = 31 ± 20 M⊙ yr− 1) z ∼ 5.5 galaxies for ...which the C ii158 μm line has been previously obtained with Atacama Large Millimeter Array (ALMA). We first fit each line with a Gaussian function and compute the residuals by subtracting the best-fitting model from the data. We combine the residuals of all sample galaxies and find that the total signal is characterized by a flux excess of ∼0.5 mJy extended over ∼1000 km s−1. Although we cannot exclude that part of this signal is due to emission from faint satellite galaxies, we show that the most probable explanation for the detected flux excess is the presence of broad wings in the C ii lines, signatures of starburst-driven outflows. We infer an average outflow rate of $\dot{M}=54\pm 23\, {\rm M}_{{\odot }} {\rm \,yr}^{-1}$, providing a loading factor $\eta =\skew4\dot{M}/{\rm SFR}=1.7\pm 1.3$ in agreement with observed local starbursts. Our interpretation is consistent with outcomes from zoomed hydrosimulations of Dahlia, a z ∼ 6 galaxy ($\rm SFR\sim 100\, \rm M_{{\odot }} \, yr^{-1}$), whose feedback-regulated star formation results into an outflow rate $\dot{M}\sim 30\, {\rm M}_{{\odot }} {\rm \,yr}^{-1}$. The quality of the ALMA data is not sufficient for a detailed analysis of the C ii line profile in individual galaxies. Nevertheless, our results suggest that starburst-driven outflows are in place in the EoR and provide useful indications for future ALMA campaigns. Deeper observations of the C ii line in this sample are required to better characterize feedback at high-z and to understand the role of outflows in shaping early galaxy formation.
Abstract
Attempts to trace star formation with rest-frame UV/optical observations at redshifts
z
> 2 are affected by the presence of potentially substantial, yet uncertain, dust attenuation. Recent ...studies have demonstrated the existence of a population of galaxies that are virtually invisible in the observed optical/near-infrared (NIR) due to dust obscuration, but which could contribute substantially to the star formation history at 2 <
z
< 6. Here, we make use of ultradeep 3 GHz Karl G. Jansky Very Large Array observations from the COSMOS-XS survey to investigate the contribution 20of radio-selected “optically dark” galaxies (undetected to a depth of
K
S
∼ 25.9 mag) to the cosmic star formation rate density (SFRD). We identify 19 such “optically dark” sources and utilize recent deblended far-infrared photometry to determine photometric redshifts based on IR and radio information for 11 of them. Through stacking, we infer that the remaining eight sources reside predominantly at high redshift (
z
> 4). Therefore, we conservatively assume these sources lie between
z
= 2 and
z
= 5. We derive the radio luminosity function (LF) for the sample with and without “optically dark” sources by fixing the faint and bright end shape of the radio LF to the local values and allowing for luminosity evolution. By integrating both LFs, we estimate the contribution of the “optically dark” galaxies to the radio SFRD to be
∼
15
−
7
+
7
%
at
z
∼ 5. This is consistent with constraints from NIR-dark and UV-dark sources, while being in disagreement with some estimates using
H
-dropouts. This result implies that “optically dark” sources play a nonnegligible role at high redshift.
Exploiting the sensitivity of the IRAM NOrthern Extended Millimeter Array (NOEMA) and its ability to process large instantaneous bandwidths, we have studied the morphology and other properties of the ...molecular gas and dust in the star forming galaxy, H-ATLAS J131611.5+281219 (HerBS-89a), at
z
= 2.95. High angular resolution (0
.
″3) images reveal a partial 1
.
″0 diameter Einstein ring in the dust continuum emission and the molecular emission lines of
12
CO(9−8) and H
2
O(2
02
− 1
11
). Together with lower angular resolution (0
.
″6) images, we report the detection of a series of molecular lines including the three fundamental transitions of the molecular ion OH
+
, namely (1
1
− 0
1
), (1
2
− 0
1
), and (1
0
− 0
1
), seen in absorption; the molecular ion CH
+
(1 − 0) seen in absorption, and tentatively in emission; two transitions of amidogen (NH
2
), namely (2
02
− 1
11
) and (2
20
− 2
11
) seen in emission; and HCN(11 − 10) and/or NH(1
2
− 0
1
) seen in absorption. The NOEMA data are complemented with Very Large Array data tracing the
12
CO(1 − 0) emission line, which provides a measurement of the total mass of molecular gas and an anchor for a CO excitation analysis. In addition, we present
Hubble
Space Telescope imaging that reveals the foreground lensing galaxy in the near-infrared (1.15
μ
m). Together with photometric data from the Gran Telescopio Canarias, we derive a photometric redshift of
z
phot
= 0.9
−0.5
+0.3
for the foreground lensing galaxy. Modeling the lensing of HerBS-89a, we reconstruct the dust continuum (magnified by a factor
μ
≃ 5.0) and molecular emission lines (magnified by
μ
∼ 4 − 5) in the source plane, which probe scales of ∼0
.
″1 (or 800 pc). The
12
CO(9 − 8) and H
2
O(2
02
− 1
11
) emission lines have comparable spatial and kinematic distributions; the source-plane reconstructions do not clearly distinguish between a one-component and a two-component scenario, but the latter, which reveals two compact rotating components with sizes of ≈1 kpc that are likely merging, more naturally accounts for the broad line widths observed in HerBS-89a. In the core of HerBS-89a, very dense gas with
n
H
2
∼ 10
7 − 9
cm
−3
is revealed by the NH
2
emission lines and the possible HCN(11 − 10) absorption line. HerBS-89a is a powerful star forming galaxy with a molecular gas mass of
M
mol
= (2.1 ± 0.4) × 10
11
M
⊙
, an infrared luminosity of
L
IR
= (4.6 ± 0.4) × 10
12
L
⊙
, and a dust mass of
M
dust
= (2.6 ± 0.2) × 10
9
M
⊙
, yielding a dust-to-gas ratio
δ
GDR
≈ 80. We derive a star formation rate SFR = 614 ± 59
M
⊙
yr
−1
and a depletion timescale
τ
depl
= (3.4 ± 1.0) × 10
8
years. The OH
+
and CH
+
absorption lines, which trace low (∼100 cm
−3
) density molecular gas, all have their main velocity component red-shifted by Δ
V
∼ 100 km s
−1
relative to the global CO reservoir. We argue that these absorption lines trace a rare example of gas inflow toward the center of a galaxy, indicating that HerBS-89a is accreting gas from its surroundings.
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