Neutral outflows in high- z QSOs Butler, Kirsty M.; van der Werf, Paul P.; Omont, Alain ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674
Journal Article
Recenzirano
Odprti dostop
The OH
+
(1
1
− 1
0
) absorption line is a powerful tracer of inflowing and outflowing gas in the predominantly atomic diffuse and turbulent halo surrounding galaxies. In this Letter, we present ...observations of OH
+
(1
1
− 1
0
), CO(9-8) and the underlying dust continuum in five strongly lensed
z
∼ 2 − 4 quasi-stellar objects (QSOs), using the Atacama Large Millimeter/submillimeter Array (ALMA) to detect outflowing neutral gas. Blue-shifted OH
+
(1
1
− 1
0
) absorption is detected in three out of five QSOs and tentatively detected in a fourth. Absorption at systemic velocities is also detected in one source also displaying blue-shifted absorption. OH
+
(1
1
− 1
0
) emission is observed in three out of five QSOs at systemic velocities and the OH
+
(2
1
− 1
0
) transition is also detected in one source. CO(9-8) is detected in all five QSOs at high S/N, providing information on the dense molecular gas within the host galaxy. We compare our sample to high-
z
far-infrared (FIR) luminous star-forming and active galaxies from the literature. We find no difference in OH
+
absorption line properties between active and star-forming galaxies with both samples roughly following the same optical depth-dust temperature relation. This suggests that these observables are driven by the same mechanism in both samples. Similarly, star-forming and active galaxies both follow the same OH
+
emission–FIR relation. Obscured QSOs display broader (> 800 km s
−1
) emission than the unobscured QSOs and all but one of the high-
z
star-forming galaxies (likely caused by the warm molecular gas reservoir obscuring the accreting nucleus). Broader CO(9-8) emission (> 500 km s
−1
) is found in obscured versus unobscured QSOs, but overall they cover a similar range in line widths as the star-forming galaxies and follow the CO(9-8)–FIR luminosity relation found in low-
z
galaxies. We find that outflows traced by OH
+
are only detected in extreme star-forming galaxies (indicated by broad CO(9-8) emission) and in both types of QSOs, which, in turn, display no red-shifted absorption. This suggests that diffuse neutral outflows in galaxy halos may be associated with the most energetic evolutionary phases leading up to and following the obscured QSO phase.
Abstract The enormous increase in mid-IR sensitivity and spatial and spectral resolution provided by the JWST spectrographs enables, for the first time, detailed extragalactic studies of molecular ...vibrational bands. This opens an entirely new window for the study of the molecular interstellar medium in luminous infrared galaxies (LIRGs). We present a detailed analysis of rovibrational bands of gas-phase CO, H 2 O, C 2 H 2 , and HCN toward the heavily obscured eastern nucleus of the LIRG VV 114, as observed by NIRSpec and the medium resolution spectrograph on the Mid-InfraRed Instrument (MIRI MRS). Spectra extracted from apertures of 130 pc in radius show a clear dichotomy between the obscured active galactic nucleus (AGN) and two intense starburst regions. We detect the 2.3 μ m CO bandheads, characteristic of cool stellar atmospheres, in the star-forming regions, but not toward the AGN. Surprisingly, at 4.7 μ m, we find highly excited CO ( T ex ≈ 700–800 K out to at least rotational level J = 27) toward the star-forming regions, but only cooler gas ( T ex ≈ 200 K) toward the AGN. We conclude that only mid-infrared pumping through the rovibrational lines can account for the equilibrium conditions found for CO and H 2 O in the deeply embedded starbursts. Here, the CO bands probe regions with an intense local radiation field inside dusty young massive star clusters or near the most massive young stars. The lack of high-excitation molecular gas toward the AGN is attributed to geometric dilution of the intense radiation from the bright point source. An overview of the relevant excitation and radiative transfer physics is provided in an appendix.
Abstract Molecular lines are powerful diagnostics of the physical and chemical properties of the interstellar medium (ISM). These ISM properties, which affect future star formation, are expected to ...differ in starburst galaxies from those of more quiescent galaxies. We investigate the ISM properties in the central molecular zone of the nearby starburst galaxy NGC 253 using the ultrawide millimeter spectral scan survey from the Atacama Large Millimeter/submillimeter Array Large Program ALCHEMI. We present an atlas of velocity-integrated images at a 1.″6 resolution of 148 unblended transitions from 44 species, including the first extragalactic detection of HCNH + and the first interferometric images of C 3 H + , NO, and HCS + . We conduct a principal component analysis (PCA) on these images to extract correlated chemical species and to identify key groups of diagnostic transitions. To the best of our knowledge, our data set is currently the largest astronomical set of molecular lines to which PCA has been applied. The PCA can categorize transitions coming from different physical components in NGC 253 such as (i) young starburst tracers characterized by high-excitation transitions of HC 3 N and complex organic molecules versus tracers of on-going star formation (radio recombination lines) and high-excitation transitions of CCH and CN tracing photodissociation regions, (ii) tracers of cloud-collision-induced shocks (low-excitation transitions of CH 3 OH, HNCO, HOCO + , and OCS) versus shocks from star formation-induced outflows (high-excitation transitions of SiO), as well as (iii) outflows showing emission from HOC + , CCH, H 3 O + , CO isotopologues, HCN, HCO + , CS, and CN. Our findings show these intensities vary with galactic dynamics, star formation activities, and stellar feedback.
Abstract
We report results from a large molecular line survey of luminous infrared galaxies (LIRGs; L
IR ≳1011L⊙) in the local Universe (z ≤ 0.1), conducted during the last decade with the James ...Clerk Maxwell Telescope and the IRAM 30-m telescope. This work presents the CO and 13CO line data for 36 galaxies, further augmented by multi-J total CO line luminosities available for other infrared (IR) bright galaxies from the literature. This yields a combined sample of N = 70 galaxies with the star formation (SF) powered fraction of their IR luminosities spanning and a wide range of morphologies. Simple comparisons of their available CO spectral line energy distributions (SLEDs) with local ones, as well as radiative transfer models, discern a surprisingly wide range of average interstellar medium (ISM) conditions, with most of the surprises found in the high-excitation regime. These take the form of global CO SLEDs dominated by a very warm (T
kin ≳100 K) and dense (n ≥ 104 cm−3) gas phase, involving galaxy-sized (∼(few) × 109 M⊙) gas mass reservoirs under conditions that are typically found only for ∼(1-3) per cent of mass per typical SF molecular cloud in the Galaxy. Furthermore, some of the highest excitation CO SLEDs are found in ultraluminous infrared galaxies (ULIRGs; L
IR ≥ 1012 L⊙) and surpass even those found solely in compact SF-powered hot spots in Galactic molecular clouds. Strong supersonic turbulence and high cosmic ray energy densities rather than far-ultraviolet/optical photons or supernova remnant induced shocks from individual SF sites can globally warm the large amounts of dense gas found in these merger-driven starbursts and easily power their extraordinary CO line excitation. This exciting possibility can now be systematically investigated with Herschel and the Atacama Large Milimeter Array (ALMA). As expected for an IR-selected (and thus SF rate selected) galaxy sample, only few 'cold' CO SLEDs are found, and for fewer still a cold low/moderate-density and gravitationally bound state (i.e. Galactic type) emerges as the most likely one. The rest remain compatible with a warm and gravitationally unbound low-density phase often found in ULIRGs. Such degeneracies, prominent when only the low-J SLED segment (J = 1-0, 2-1 and 3-2) is available, advise against using its CO line ratios and the so-called X
co = M(H2)/L
co(1-0) factor as SF mode indicators, a practice that may have led to the misclassification of the ISM environments of IR-selected gas-rich discs in the distant Universe. Finally, we expect that the wide range of ISM conditions found among LIRGs will strongly impact the X
co factor, an issue we examine in detail in Paper II.
Abstract
Molecular abundances are sensitive to the UV photon flux and cosmic-ray ionization rate. In starburst environments, the effects of high-energy photons and particles are expected to be ...stronger. We examine these astrochemical signatures through multiple transitions of HCO
+
and its metastable isomer HOC
+
in the center of the starburst galaxy NGC 253 using data from the Atacama Large Millimeter/submillimeter Array large program ALMA Comprehensive High-resolution Extragalactic Molecular inventory. The distribution of the HOC
+
(1−0) integrated intensity shows its association with “superbubbles,” cavities created either by supernovae or expanding H
ii
regions. The observed HCO
+
/HOC
+
abundance ratios are ∼10–150, and the fractional abundance of HOC
+
relative to H
2
is ∼1.5 × 10
−11
–6 × 10
−10
, which implies that the HOC
+
abundance in the center of NGC 253 is significantly higher than in quiescent spiral arm dark clouds in the Galaxy and the Galactic center clouds. Comparison with chemical models implies either an interstellar radiation field of
G
0
≳ 10
3
if the maximum visual extinction is ≳5, or a cosmic-ray ionization rate of
ζ
≳ 10
−14
s
−1
(3–4 orders of magnitude higher than that within clouds in the Galactic spiral arms) to reproduce the observed results. From the difference in formation routes of HOC
+
, we propose that a low-excitation line of HOC
+
traces cosmic-ray dominated regions, while high-excitation lines trace photodissociation regions. Our results suggest that the interstellar medium in the center of NGC 253 is significantly affected by energy input from UV photons and cosmic rays, sources of energy feedback.
The cosmic-ray ionization rate (CRIR) is a key parameter in understanding the physical and chemical processes in the interstellar medium. Cosmic rays are a significant source of energy in star ...formation regions, impacting the physical and chemical processes that drive the formation of stars. Previous studies of the circum-molecular zone of the starburst galaxy NGC 253 have found evidence for a high CRIR value: 103–106 times the average CRIR within the Milky Way. This is a broad constraint, and one goal of this study is to determine this value with much higher precision. We exploit ALMA observations toward the central molecular zone of NGC 253 to measure the CRIR. We first demonstrate that the abundance ratio of H3O+ and SO is strongly sensitive to the CRIR. We then combine chemical and radiative transfer models with nested sampling to infer the gas properties and CRIR of several star-forming regions in NGC 253 from emission from their transitions. We find that each of the four regions modeled has a CRIR in the range (1–80) × 10−14 s−1 and that this result adequately fits the abundances of other species that are believed to be sensitive to cosmic rays, including C2H, HCO+, HOC+, and CO. From shock and photon-dominated/X-ray dominated region models, we further find that neither UV-/X-ray-driven nor shock-dominated chemistry is a viable single alternative as none of these processes can adequately fit the abundances of all of these species.
Abstract
We have used the Submillimeter Array (SMA) at 860 $\mu$m to observe the brightest sources in the Submillimeter Common User Bolometer Array-2 (SCUBA-2) Cosmology Legacy Survey (S2CLS). The ...goal of this survey is to exploit the large field of the S2CLS along with the resolution and sensitivity of the SMA to construct a large sample of these rare sources and to study their statistical properties. We have targeted 70 of the brightest single-dish SCUBA-2 850 $\mu$m sources down to S850 ≈ 8 mJy, achieving an average synthesized beam of 2.4 arcsec and an average rms of σ860 = 1.5 mJy beam−1 in our primary beam-corrected maps. We searched our SMA maps for 4σ peaks, corresponding to S860 ≳ 6 mJy sources, and detected 62, galaxies, including three pairs. We include in our study 35 archival observations, bringing our sample size to 105 bright single-dish submillimetre sources with interferometric follow-up. We compute the cumulative and differential number counts, finding them to overlap with previous single-dish survey number counts within the uncertainties, although our cumulative number count is systematically lower than the parent S2CLS cumulative number count by 14 ± 6 per cent between 11 and 15 mJy. We estimate the probability that a ≳10 mJy single-dish submillimetre source resolves into two or more galaxies with similar flux densities to be less than 15 per cent. Assuming the remaining 85 per cent of the targets are ultraluminous starburst galaxies between z = 2 and 3, we find a likely volume density of ≳400 M⊙ yr−1 sources to be ${\sim }\,3^{+0.7}_{-0.6}\,{\times }\,10^{-7}$ Mpc−3. We show that the descendants of these galaxies could be ≳4 × 1011 M⊙ local quiescent galaxies, and that about 10 per cent of their total stellar mass would have formed during these short bursts of star formation.
Abstract
We present the results from our Atacama Large Millimeter/submillimeter Array (ALMA) imaging observations of the CO(7−6), C
i
370
μ
m (hereafter C
i
), and N
ii
205
μ
m (hereafter N
ii
) ...lines and their underlying continuum emission of BRI 1335-0417, an infrared bright quasar at
z
= 4.407. At the achieved resolutions of ∼1.″1 to 1.″2 (or 7.5–8.2 kpc), the continuum at 205 and 372
μ
m (rest frame), the CO(7−6), and the C
i
emissions are at best barely resolved whereas the N
ii
emission is well resolved with a beam-deconvolved major axis of 1.″3(±0.″3) or 9(±2) kpc. As a warm dense gas tracer, the CO(7−6) emission shows a more compact spatial distribution and a significantly higher peak velocity dispersion than the other two lines that probe lower density gas, a picture favoring a merger-triggered star formation (SF) scenario over an orderly rotating SF disk. The CO(7−6) data also indicate a possible QSO-driven gas outflow that reaches a maximum line-of-sight velocity of 500–600 km s
−1
. The far-infrared (FIR) dust temperature (
T
dust
) of 41.5 K from a graybody fit to the continuum agrees well with the average
T
dust
inferred from various line luminosity ratios. The resulting
L
CO(7–6)
/
L
FIR
luminosity ratio is consistent with that of local luminous infrared galaxies powered predominantly by SF. The
L
CO(7–6)
-inferred SF rate is 5.1(±1.5) × 10
3
M
⊙
yr
−1
. The system has an effective star-forming region of
kpc in diameter and a molecular gas reservoir of ∼5 × 10
11
M
⊙
.
Abstract
We present a spatially resolved excitation analysis for the central molecular zone (CMZ) of the starburst galaxy NGC 253 using the data from the Atacama Large Millimeter/submillimeter Array ...Comprehensive High-resolution Extragalactic Molecular Inventory, whereby we explore parameters distinguishing NGC 253 from the quiescent Milky Way’s Galactic center (GC). Non-LTE analyses employing a hierarchical Bayesian framework are applied to Band 3–7 transitions from nine molecular species to delineate the position–position–velocity distributions of column density (
N
H
2
), volume density (
n
H
2
), and temperature (
T
kin
) at 27 pc resolution. Two distinct components are detected: a low-density component with
(
n
H
2
,
T
kin
)
∼
(
10
3.3
cm
−
3
,
85
K
)
and a high-density component with
(
n
H
2
,
T
kin
)
∼
(
10
4.4
cm
−
3
,
110
K
)
, separated at
n
H
2
∼
10
3.8
cm
−
3
. NGC 253 has ∼10 times the high-density gas mass and ∼3 times the dense-gas mass fraction of the GC. These properties are consistent with their HCN/CO ratio but cannot alone explain the factor of ∼30 difference in their star formation efficiencies (SFEs), contradicting the dense-gas mass to star formation rate scaling law. The
n
H
2
histogram toward NGC 253 exhibits a shallow declining slope up to
n
H
2
∼
10
6
cm
−
3
, while that of the GC steeply drops in
n
H
2
≳
10
4.5
cm
−
3
and vanishes at 10
5
cm
−3
. Their dense-gas mass fraction ratio becomes consistent with their SFEs when the threshold
n
H
2
for the dense gas is taken at ∼10
4.2−4.6
cm
−3
. The rich abundance of gas above this density range in the NGC 253 CMZ, or its scarcity in the GC, is likely to be the critical difference characterizing the contrasting star formation in the centers of the two galaxies.
ABSTRACT
We present new ALMA Band 8 (rest-frame $90 \ \mu$m) continuum observations of three massive ($M_\star \approx 10^{10}\ \mathrm{ M}_\odot$) galaxies at z ≈ 7 previously detected in C ii$158 \ ...\mu$m and underlying dust continuum emission in the Reionization Era Bright Emission Line Survey (REBELS). We detect dust emission from two of our targets in Band 8 (REBELS-25 and REBELS-38), while REBELS-12 remains undetected. Through optically thin modified blackbody fitting, we determine dust temperatures of $T_\mathrm{dust}\approx 30-35\,$ K in both of the dual-band detected targets, indicating they are colder than most known galaxies at z ∼ 7. Moreover, their inferred dust masses are large ($M_\mathrm{dust}\approx 10^{8}\ \mathrm{ M}_\odot$), albeit still consistent with models of high-redshift dust production. We furthermore target and detect O iii$88 \ \mu$m emission in both REBELS-12 and REBELS-25, and find $L_\mathrm{O\, III}/L_\mathrm{C\, II}\approx 1-1.5$ – low compared to the $L_\mathrm{O\, \rm{\small III}}/L_\mathrm{C\, \rm{\small II}}\gtrsim 2-10$ observed in the known z ≳ 6 population thus far. We argue the lower line ratios are due to a comparatively weaker ionizing radiation field resulting from the less starbursty nature of our targets, although the possibility of REBELS-12 being a merger of an O iii-bright and O iii-faint component prevents the unambiguous interpretation of its O iii/C ii ratio. Nevertheless, a low burstiness forms a natural explanation for the cold dust temperatures and low $\mathrm{O\, \rm{\small III}}\lambda \lambda 4959,5007+\mathrm{H} \, \beta$ equivalent widths of REBELS-25 and REBELS-38. Overall, these observations provide evidence for the existence of a massive, dust-rich galaxy population at z ≈ 7 which has previously experienced vigorous star formation, but is currently forming stars in a steady, as opposed to bursty, manner.
PDF
![CO (7−6), [C i] 370 μm, and...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0004-637X/small "CO (7−6), [C i] 370 μm, and [N ii] 205 μm Line Emission of the QSO BRI 1335-0417 at Redshift 4.407")