The most intensively star-forming galaxies are extremely luminous at far-infrared (FIR) wavelengths, highly obscured at optical and ultraviolet wavelengths, and lie at z ≥ 1-3. We present a programme ...of FIR spectroscopic observations with the SPIRE FTS, as well as photometric observations with PACS, both on board Herschel, towards a sample of 45 gravitationally lensed, dusty starbursts across z ∼ 1-3.6. In total, we detected 27 individual lines down to 3 σ, including nine C II 158 μm lines with confirmed spectroscopic redshifts, five possible C II lines consistent with their FIR photometric redshifts, and in some individual sources a few O III 88 μm, O III 52 μm, O I 145 μm, O I 63 μm, N II 122 μm and OH 119 μm (in absorption) lines. To derive the typical physical properties of the gas in the sample, we stack all spectra weighted by their intrinsic luminosity and by their 500μm flux densities, with the spectra scaled to a common redshift. In the stacked spectra, we detect emission lines of C II 158 μm, N II 122 μm, O III 88 μm, O III 52 μm, O I 63 μm and the absorption doublet of OH at 119 μm, at high fidelity. We find that the average electron densities traced by the N II and O III lines are higher than the average values in local star-forming galaxies and ULIRGs, using the same tracers. From the N II/C II and O I/C II ratios, we find that the C II emission is likely dominated by the photodominated regions (PDR), instead of by ionized gas or large-scale shocks.
We use a suite of eight ocean biogeochemical/ecological general circulation models from the Marine Ecosystem Model Intercomparison Project and Coupled Model Intercomparison Project Phase 5 archives ...to explore the relative roles of changes in winds (positive trend of Southern Annular Mode, SAM) and in warming‐ and freshening‐driven trends of upper ocean stratification in altering export production and CO2 uptake in the Southern Ocean at the end of the 21st century. The investigated models simulate a broad range of responses to climate change, with no agreement on a dominance of either the SAM or the warming signal south of 44°S. In the southernmost zone, i.e., south of 58°S, they concur on an increase of biological export production, while between 44 and 58°S the models lack consensus on the sign of change in export. Yet in both regions, the models show an enhanced CO2 uptake during spring and summer. This is due to a larger CO2(aq) drawdown by the same amount of summer export production at a higher Revelle factor at the end of the 21st century. This strongly increases the importance of the biological carbon pump in the entire Southern Ocean. In the temperate zone, between 30 and 44°S, all models show a predominance of the warming signal and a nutrient‐driven reduction of export production. As a consequence, the share of the regions south of 44°S to the total uptake of the Southern Ocean south of 30°S is projected to increase at the end of the 21st century from 47 to 66% with a commensurable decrease to the north. Despite this major reorganization of the meridional distribution of the major regions of uptake, the total uptake increases largely in line with the rising atmospheric CO2. Simulations with the MITgcm‐REcoM2 model show that this is mostly driven by the strong increase of atmospheric CO2, with the climate‐driven changes of natural CO2 exchange offsetting that trend only to a limited degree (∼10%) and with negligible impact of climate effects on anthropogenic CO2 uptake when integrated over a full annual cycle south of 30°S.
Key Points
Increase of CO2 uptake driven by anthropogenic carbon, not by climate change
A higher Revelle factor causes enhanced biologically driven CO2 uptake in summer
The southern Southern Ocean becomes more important for total CO2 uptake
Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we conducted a program to measure redshifts for 13 bright galaxies detected in the
Herschel
Astrophysical Large Area Survey with
S
500
μ
m
...≥ 80 mJy. We report reliable spectroscopic redshifts for 12 individual sources, which are derived from scans of the 3 and 2 mm bands, covering up to 31 GHz in each band, and are based on the detection of at least two emission lines. The spectroscopic redshifts are in the range 2.08 <
z
< 4.05 with a median value of
z
= 2.9 ± 0.6. The sources are unresolved or barely resolved on scales of 10 kpc. In one field, two galaxies with different redshifts were detected. In two cases the sources are found to be binary galaxies with projected distances of ∼140 kpc. The linewidths of the sources are large, with a mean value for the full width at half maximum of 700 ± 300 km s
−1
and a median of 800 km s
−1
. We analyze the nature of the sources with currently available ancillary data to determine if they are lensed or hyper-luminous (
L
FIR
> 10
13
L
⊙
) galaxies. We also present a reanalysis of the spectral energy distributions including the continuum flux densities measured at 3 and 2 mm to derive the overall properties of the sources. Future prospects based on these efficient measurements of redshifts of high-
z
galaxies using NOEMA are outlined, including a comprehensive survey of all the brightest
Herschel
galaxies.
ABSTRACT
We report observations with the Atacama Large Millimetre Array (ALMA) of six submillimetre galaxies (SMGs) within 3 arcmin of the Distant Red Core (DRC) at z = 4.0, a site of intense ...cluster-scale star formation, first reported by Oteo et al. We find new members of DRC in three SMG fields; in two fields, the SMGs are shown to lie along the line of sight towards DRC; one SMG is spurious. Although at first sight this rate of association is consistent with earlier predictions, associations with the bright SMGs are rarer than expected, which suggests caution when interpreting continuum overdensities. We consider the implications of all 14 confirmed DRC components passing simultaneously through an active phase of star formation. In the simplest explanation, we see only the tip of the iceberg in terms of star formation and gas available for future star formation, consistent with our remarkable finding that the majority of newly confirmed DRC galaxies are not the brightest continuum emitters in their immediate vicinity. Thus, while ALMA continuum follow-up of SMGs identifies the brightest continuum emitters in each field, it does not necessarily reveal all the gas-rich galaxies. To hunt effectively for protocluster members requires wide and deep spectral-line imaging to uncover any relatively continuum-faint galaxies that are rich in atomic or molecular gas. Searching with short-baseline arrays or single-dish facilities, the true scale of the underlying gas reservoirs may be revealed.
We present Low-Frequency Array (LOFAR) High-Band Array observations of the Herschel-ATLAS North Galactic Pole survey area. The survey we have carried out, consisting of four pointings covering around ...142 deg2 of sky in the frequency range 126–173 MHz, does not provide uniform noise coverage but otherwise is representative of the quality of data to be expected in the planned LOFAR wide-area surveys, and has been reduced using recently developed ‘facet calibration’ methods at a resolution approaching the full resolution of the data sets (∼10 × 6 arcsec) and an rms off-source noise that ranges from 100 μJy beam−1 in the centre of the best fields to around 2 mJy beam−1 at the furthest extent of our imaging. We describe the imaging, cataloguing and source identification processes, and present some initial science results based on a 5σ source catalogue. These include (i) an initial look at the radio/far-infrared correlation at 150 MHz, showing that many Herschel sources are not yet detected by LOFAR; (ii) number counts at 150 MHz, including, for the first time, observational constraints on the numbers of star-forming galaxies; (iii) the 150-MHz luminosity functions for active and star-forming galaxies, which agree well with determinations at higher frequencies at low redshift, and show strong redshift evolution of the star-forming population; and (iv) some discussion of the implications of our observations for studies of radio galaxy life cycles.
We present images obtained with LABOCA of a sample of 22 galaxies selected via their red Herschel SPIRE colors. We aim to see if these luminous, rare, and distant galaxies are signposting dense ...regions in the early universe. Our 870 m survey covers an area of 1 deg2 down to an average rms of , with our five deepest maps going 2× deeper still. We catalog 86 dusty star-forming galaxies (DSFGs) around our "signposts," detected above a significance of 3.5 . This implies a overdensity of (or ) DSFGs, excluding our signposts, when comparing our number counts to those in "blank fields." Thus, we are 99.93% confident that our signposts are pinpointing overdense regions in the universe, and 95% 50% confident that these regions are overdense by a factor of at least ≥1.5 × 2×. Using template spectral energy distributions (SEDs) and SPIRE/LABOCA photometry, we derive a median photometric redshift of z = 3.2 0.2 for our signposts, with an inter-quartile range of z = 2.8-3.6, somewhat higher than expected for ∼850 m selected galaxies. We constrain the DSFGs that are likely responsible for this overdensity to within of their respective signposts. These "associated" DSFGs are radially distributed within (physical) distances of 1.6 0.5 Mpc from their signposts, have median star formation rates (SFRs) of (for a Salpeter stellar inital mass function) and median gas reservoirs of . These candidate protoclusters have average total SFRs of at least and space densities of ∼9 × 10−7 Mpc−3, consistent with the idea that their constituents may evolve to become massive early-type galaxies in the centers of the rich galaxy clusters we see today.
Abstract
We have modelled ∼0.1 arcsec resolution Atacama Large Millimetre/submillimeter Array imaging of six strong gravitationally lensed galaxies detected by the Herschel Space Observatory. Our ...modelling recovers mass properties of the lensing galaxies and, by determining magnification factors, intrinsic properties of the lensed submillimetre sources. We find that the lensed galaxies all have high ratios of star formation rate to dust mass, consistent with or higher than the mean ratio for high-redshift submillimetre galaxies and low-redshift ultra-luminous infrared galaxies. Source reconstruction reveals that most galaxies exhibit disturbed morphologies. Both the cleaned image plane data and the directly observed interferometric visibilities have been modelled, enabling comparison of both approaches. In the majority of cases, the recovered lens models are consistent between methods, all six having mass density profiles that are close to isothermal. However, one system with poor signal to noise shows mildly significant differences.
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.
We present high-resolution maps of stars, dust, and molecular gas in a strongly lensed submillimeter galaxy (SMG) at z = 3.259. HATLAS J114637.9-001132 is selected from the Herschel-Astrophysical ...Terahertz Large Area Survey (H-ATLAS) as a strong lens candidate mainly based on its unusually high 500 mu m flux density (~300 mJy). It is the only high-redshift Planck detection in the 130 deg super(2) H-ATLAS Phase-I area. Keck Adaptive Optics images reveal a quadruply imaged galaxy in the K band while the Submillimeter Array and the Jansky Very Large Array show doubly imaged 880 mu m and CO(1 arrow right 0) sources, indicating differentiated distributions of the various components in the galaxy. In the source plane, the stars reside in three major kpc-scale clumps extended over ~1.6 kpc, the dust in a compact (~1 kpc) region ~3 kpc north of the stars, and the cold molecular gas in an extended (~7 kpc) disk ~5 kpc northeast of the stars. The emissions from the stars, dust, and gas are magnified by ~17, ~8, and ~7 times, respectively, by four lensing galaxies at z ~ 1. Intrinsically, the lensed galaxy is a warm (T sub(dust) ~ 40-65 K), hyper-luminous (L sub(IR) ~ 1.7 x 10 super(13) L sub(middot in circle); star formation rate (SFR) ~ 2000 M sub(middot in circle) yr super(-1)), gas-rich (M sub(gas)/M sub(baryon) ~ 70%), young (M sub(stellar)/SFR ~ 20 Myr), and short-lived (M sub(gas)/SFR ~ 40 Myr) starburst. With physical properties similar tounlensed z > 2 SMGs, HATLAS J114637.9-001132 offers a detailed view of a typical SMG through a powerful cosmic microscope.
We report measurements of the carbon monoxide ground state rotational transition ( super(12)C super(16)O J = 1-0) with the Zpectrometer ultrawideband spectrometer on the 100 m diameter Green Bank ...Telescope. The sample comprises 11 galaxies with redshifts between z = 2.1 and 3.5 from a total sample of 24 targets identified by Herschel-ATLAS photometric colors from the SPIRE instrument. Nine of the CO measurements are new redshift determinations, substantially adding to the number of detections of galaxies with rest-frame peak submillimeter emission near 100 mu m. The CO detections confirm the existence of massive gas reservoirs within these luminous dusty starforming galaxies (DSFGs). The CO redshift distribution of the 350 mu m selected galaxies is strikingly similar to the optical redshifts of 850 mu -selected submillimeter galaxies in 2.1 < or =, slanted z < or = z, slanted 3.5. Spectroscopic redshifts break a temperature-redshift degeneracy; optically thin dust models fit to the far-infrared photometry indicate characteristic dust temperatures near 34 K for most of the galaxies we detect in CO. Detections of two warmer galaxies, and statistically significant nondetections, hint at warmer or molecule-poor DSFGs with redshifts that are difficult to determine from Herschel-SPIRE photometric colors alone. Many of the galaxies identified by H-ATLAS photometry are expected to be amplified by foreground gravitational lenses. Analysis of CO linewidths and luminosities provides a method for finding approximate gravitational lens magnifications mu from spectroscopic data alone, yielding mu ~ 3-20. Corrected for magnification, most galaxy luminosities are consistent with an ultraluminous infrared galaxy classification, but three are candidate hyper-LIRGs with luminosities greater than 10 super(13) L sub(middot in circle).
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