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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Rise of the Titans: Gas Excitation and Feedback in a Binary Hyperluminous Dusty Starburst Galaxy at z ∼ 6
Abstract We report new observations toward the hyperluminous dusty starbursting major merger ADFS-27 ( z = 5.655), using the Australia Telescope Compact Array (ATCA) and the Atacama Large Millimeter/submillimeter Array (ALMA). We detect CO ( J = 2 → 1), CO ( J = 8 → 7), CO ( J = 9 → 8), CO ( J = 10 → 9), and H 2 O (3 12 → 2 21 ) emission, and a P Cygni−shaped OH + (1 1 → 0 1 ) absorption/emission feature. We also tentatively detect H 2 O (3 21 → 3 12 ) and OH + (1 2 → 0 1 ) emission and CH + ( J = 1 → 0) absorption. We find a total cold molecular mass of M gas = (2.1 ± 0.2) × 10 11 ( α CO /1.0) M ⊙ . We also find that the excitation of the star-forming gas is overall moderate for a z > 5 dusty starburst, which is consistent with its moderate dust temperature. A high-density, high kinetic temperature gas component embedded in the gas reservoir is required to fully explain the CO line ladder. This component is likely associated with the “maximum starburst” nuclei in the two merging galaxies, which are separated by only 140 ± 13 km s −1 along the line of sight and 9.0 kpc in projection. The kinematic structure of both components is consistent with galaxy disks, but this interpretation remains limited by the spatial resolution of the current data. The OH + features are only detected toward the northern component, which is also the one that is more enshrouded in dust and thus remains undetected up to 1.6 μ m even in our sensitive new Hubble Space Telescope Wide Field Camera 3 imaging. The absorption component of the OH + line is blueshifted and peaks near the CO and continuum emission peak, while the emission is redshifted and peaks offset by 1.7 kpc from the CO and continuum emission peak, suggesting that the gas is associated with a massive molecular outflow from the intensely star-forming nucleus that supplies 125 M ⊙ yr −1 of enriched gas to its halo.
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- Award ID(s):
- 1910107
- NSF-PAR ID:
- 10330876
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 907
- Issue:
- 2
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 62
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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We present Atacama Large Millimeter/submillimeter Array (ALMA) sub-kiloparsec- to kiloparsec-scale resolution observations of the [C
II ], CO (9–8), and OH+(11–01) lines along with their dust continuum emission toward the far-infrared (FIR) luminous quasar SDSS J231038.88+185519.7 atz = 6.0031, to study the interstellar medium distribution, the gas kinematics, and the quasar-host system dynamics. We decompose the intensity maps of the [CII ] and CO (9–8) lines and the dust continuum with two-dimensional elliptical Sérsic models. The [CII ] brightness follows a flat distribution with a Sérsic index of 0.59. The CO (9–8) line and the dust continuum can be fit with an unresolved nuclear component and an extended Sérsic component with a Sérsic index of ∼1, which may correspond to the emission from an active galactic nucleus dusty molecular torus and a quasar host galaxy, respectively. The different [CII ] spatial distribution may be due to the effect of the high dust opacity, which increases the FIR background radiation on the [CII ] line, especially in the galaxy center, significantly suppressing the [CII ] emission profile. The dust temperature drops with distance from the center. The effective radius of the dust continuum is smaller than that of the line emission and the dust mass surface density, but is consistent with that of the star formation rate surface density. This may indicate that the dust emission is a less robust tracer of the dust and gas distribution but is a decent tracer of the obscured star formation activity. The OH+(11–01) line shows a P-Cygni profile with an absorption at ∼–400 km s−1, which may indicate an outflow with a neutral gas mass of (6.2 ± 1.2)×108M ⊙along the line of sight. We employed a three-dimensional tilted ring model to fit the [CII ] and CO (9–8) data cubes. The two lines are both rotation dominated and trace identical disk geometries and gas motions. This suggest that the [CII ] and CO (9–8) gas are coplanar and corotating in this quasar host galaxy. The consistent circular velocities measured with [CII ] and CO (9–8) lines indicate that these two lines trace a similar gravitational potential. We decompose the circular rotation curve measured from the kinematic model fit to the [CII ] line into four matter components (black hole, stars, gas, and dark matter). The quasar-starburst system is dominated by baryonic matter inside the central few kiloparsecs. We constrain the black hole mass to be 2.97+0.51-0.77 × 109M ⊙; this is the first time that the dynamical mass of a black hole has been measured atz ∼ 6. This mass is consistent with that determined using the scaling relations from quasar emission lines. A massive stellar component (on the order of 109M ⊙) may have already existed when the Universe was only ∼0.93 Gyr old. The relations between the black hole mass and the baryonic mass of this quasar indicate that the central supermassive black hole may have formed before its host galaxy. -
Abstract We report the detection of 23 OH + 1 → 0 absorption, emission, or P-Cygni-shaped lines and CO( J = 9→8) emission lines in 18 Herschel-selected z = 2–6 starburst galaxies with the Atacama Large Millimeter/submillimeter Array and the NOrthern Extended Millimeter Array, taken as part of the Gas And Dust Over cosmic Time Galaxy Survey. We find that the CO( J = 9→8) luminosity is higher than expected based on the far-infrared luminosity when compared to nearby star-forming galaxies. Together with the strength of the OH + emission components, this may suggest that shock excitation of warm, dense molecular gas is more prevalent in distant massive dusty starbursts than in nearby star-forming galaxies on average, perhaps due to an impact of galactic winds on the gas. OH + absorption is found to be ubiquitous in massive high-redshift starbursts, and is detected toward 89% of the sample. The majority of the sample shows evidence for outflows or inflows based on the velocity shifts of the OH + absorption/emission, with a comparable occurrence rate of both at the resolution of our observations. A small subsample appears to show outflow velocities in excess of their escape velocities. Thus, starburst-driven feedback appears to be important in the evolution of massive galaxies in their most active phases. We find a correlation between the OH + absorption optical depth and the dust temperature, which may suggest that warmer starbursts are more compact and have higher cosmic-ray energy densities, leading to more efficient OH + ion production. This is in agreement with a picture in which these high-redshift galaxies are “scaled-up” versions of the most intense nearby starbursts.more » « less
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We report the serendipitous discovery of a dusty, starbursting galaxy at z=5.667 (called CRLE hereafter), in close physical association to the "normal" Main Sequence galaxy HZ10 at z=5.654. CRLE was identified by detection of [CII], [NII] and CO(2-1) line emission, making it the highest redshift, most luminous starburst in the COSMOS field. This massive, dusty galaxy appears to be forming stars at a rate of at least 1500$\,M_\odot$ yr$^{-1}$ in a compact region only ~3 kpc in diameter. The dynamical and dust emission properties of CRLE suggest an ongoing merger driving the starburst, in a potentially intermediate stage relative to other known dusty galaxies at the same epoch. The ratio of [CII] to [NII] may suggest that an important contribution to the [CII] emission comes from a diffuse ionized gas component, which could be more extended than the dense, starbursting gas. CRLE appears to be located in a significant galaxy overdensity at the same redshift, potentially associated with a large scale cosmic structure recently identified in a Lyman Alpha Emitter survey. This overdensity suggests that CRLE and HZ10 reside in a protocluster environment, offering the tantalizing opportunity to study the effect of a massive starburst on protocluster star formation. Our findings support the interpretation that a significant fraction of the earliest galaxy formation may occur from the inside-out, within the central regions of the most massive halos, while rapidly evolving into the massive galaxy clusters observed in the local Universe.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3847/1538-4357/abcf2e
