Molecular Gas Mass Research Articles

JWST reveals star formation across a spiral arm in M33

ABSTRACT Young stellar objects (YSOs) are the gold standard for tracing star formation in galaxies but have been unobservable beyond the Milky Way and Magellanic Clouds. But that all changed when the JWST was launched, which we use to identify YSOs in the Local Group galaxy M33, marking the first time that individual YSOs have been identified at these large distances. We present Mid-Infrared Instrument (MIRI) imaging mosaics at 5.6 and 21 $\mu$m that cover a significant portion of one of M33’s spiral arms that has existing panchromatic imaging from the Hubble Space Telescope and deep Atacama Large Millimeter/submillimeter Array CO measurements. Using these MIRI and Hubble Space Telescope images, we identify point sources using the new dolphot MIRI module. We identify 793 candidate YSOs from cuts based on colour, proximity to giant molecular clouds (GMCs), and visual inspection. Similar to Milky Way GMCs, we find that higher mass GMCs contain more YSOs and YSO emission, which further show YSOs identify star formation better than most tracers that cannot capture this relationship at cloud scales. We find evidence of enhanced star formation efficiency in the southern spiral arm by comparing the YSOs to the molecular gas mass.

J0107a: A Barred Spiral Dusty Star-forming Galaxy at z = 2.467

Dusty star-forming galaxies (DSFGs) are among the most massive and active star-forming galaxies during the cosmic noon. Theoretical studies have proposed various formation mechanisms of DSFGs, including major merger-driven starbursts and secular star-forming disks. Here, we report J0107a, a bright (∼8 mJy at observed-frame 888 μm) DSFG at z = 2.467 that appears to be a gas-rich massive disk and might be an extreme case of the secular disk scenario. J0107a has a stellar mass M ⋆ ∼ 5 × 1011 M ⊙, molecular gas mass M mol ≳ 1011 M ⊙, and a star formation rate of ∼500M ⊙ yr−1. J0107a does not have a gas-rich companion. The rest-frame 1.28 μm JWST NIRCam image of J0107a shows a grand-design spiral with a prominent stellar bar extending ∼15 kpc. The Atacama Large Millimeter/submillimeter Array Band 7 continuum map reveals that the dust emission originates from both the central starburst and the stellar bar. 3D disk modeling of the CO(4–3) emission line indicates a dynamically cold disk with rotation-to-dispersion ratio . The results suggest a bright DSFG may have a nonmerger origin, and its vigorous star formation may be triggered by the bar and/or rapid gas inflow.

The Gas Accretion Rate of Galaxies over z ≈ 0–1.3

We present here estimates of the average rates of accretion of neutral gas onto main-sequence galaxies and the conversion of atomic gas to molecular gas in these galaxies at two key epochs in galaxy evolution: (i) z ≈ 1.3–1.0, toward the end of the epoch of peak star formation activity in the Universe, and (ii) z ≈ 1–0, when the star formation activity declines by an order of magnitude. We determine the net gas accretion rate R Acc and the molecular gas formation rate R Mol by combining the relations between the stellar mass and the atomic gas mass, the molecular gas mass, and the star formation rate (SFR) at three epochs, z = 1.3, z = 1.0, and z = 0, with the assumption that galaxies evolve continuously on the star-forming main sequence. We find that, for all galaxies, R Acc is far lower than the average SFR R SFR at z ≈ 1.3–1.0; however, R Mol is similar to R SFR during this interval. Conversely, both R Mol and R Acc are significantly lower than R SFR over the later interval, z ≈ 1–0. We find that massive main-sequence galaxies had already acquired most of their present-day baryonic mass by z ≈ 1.3. At z ≈ 1.3–1.0, the rapid conversion of the existing atomic gas to molecular gas was sufficient to maintain a high average SFR, despite the low net gas accretion rate. However, at later times, the combination of the lower net gas accretion rate and the lower molecular gas formation rate leads to a decline in the fuel available for star formation and results in the observed decrease in the SFR density of the Universe over the last 8 Gyr.

Decomposition of the central structure of NGC 2273 in the NIR: A case study

AbstractThe Seyfert 2 galaxy NGC 2273 is a prime target to explore how active nuclei can be fed. It has a star‐forming innermost nuclear ring with a radius of 0.33kpc from where material may be funneled to the supermassive black hole in its center. In this article, we discuss high‐resolution adaptive optics aided JHKs images of NGC 2273 taken with the Large Binocular Telescope. Using Galfit we decomposed the innermost part of NGC 2273 into a core, a disk, and a ring using 58 parameters, 44 of them were used to describe the ring. The stellar mass of the ring was found to be 12 , a factor of 10 higher than its molecular gas mass. A continuous gas flow via the main stellar bar of NGC 2273 during the lifetime of the bar of up to 10 is required to provide the fuel for the formation of the stars unless the star formation efficiency is on the order of 10%. This does not affect the fueling of the nuclear source as the amount of molecular gas required for this low‐luminosity active galaxy to achieve this is on the order of only.

12CO and 13CO observation of the low-metallicity dwarf galaxy DDO 154

Abstract The conversion factor from carbon monoxide (CO) intensity to molecular gas mass is a source of large uncertainty in understanding gas and its relation to star formation in galaxies. In particular, the conversion factor in low-metallicity environments have remained elusive, as currently only two galaxies have been detected in any CO isotopes in environments with 12 + log (O$/$H) < 8.0. Here we report 12CO (J = 1–0) and 13CO (J = 1–0) observations towards a star-forming region in DDO 154, a low-metallicity dwarf irregular galaxy at 12 + log (O$/$H) = 7.67. This is a re-observation of a previous non-detection at higher angular and velocity resolution. No significant emission was detected. By estimating the molecular gas mass from associated star formation, we find that DDO 154 has a conversion factor of more than 103 times the Milky Way. Alternatively, if we estimate molecular mass using dust continuum emission, the conversion factor is at least 2 orders of magnitude larger than the Milky Way. These estimates signify a large amount of CO-dark molecular gas in this galaxy.

Quasar feedback survey: molecular gas affected by central outflows and by ∼10-kpc radio lobes reveal dual feedback effects in ‘radio quiet’ quasars

ABSTRACT We present a study of molecular gas, traced via CO (3–2) from Atacama Large Millimeter/submillimeter Array data, of four z < 0.2, ‘radio quiet’, type 2 quasars (Lbol ∼ 1045.3–1046.2 erg s−1; L$_{\mathrm{1.4\, GHz}}\sim 10^{23.7}\!-\!10^{24.3}$ W Hz−1). Targets were selected to have extended radio lobes (≥ 10 kpc), and compact, moderate-power jets (1–10 kpc; Pjet ∼ 1043.2–1043.7 erg s−1). All targets show evidence of central molecular outflows, or injected turbulence, within the gas discs (traced via high-velocity wing components in CO emission-line profiles). The inferred velocities (Vout = 250–440 km s−1) and spatial scales (0.6–1.6 kpc), are consistent with those of other samples of luminous low-redshift active galactic nuclei. In two targets, we observe extended molecular gas structures beyond the central discs, containing 9–53 per cent of the total molecular gas mass. These structures tend to be elongated, extending from the core, and wrap-around (or along) the radio lobes. Their properties are similar to the molecular gas filaments observed around radio lobes of, mostly ‘radio loud’, brightest cluster galaxies. They have the following: projected distances of 5–13 kpc; bulk velocities of 100–340 km s−1; velocity dispersion of 30–130 km s−1; inferred mass outflow rates of 4–20 M⊙ yr−1; and estimated kinetic powers of 1040.3–1041.7 erg s−1. Our observations are consistent with simulations that suggest moderate-power jets can have a direct (but modest) impact on molecular gas on small scales, through direct jet–cloud interactions. Then, on larger scales, jet-cocoons can push gas aside. Both processes could contribute to the long-term regulation of star formation.

Evidence for Large-scale, Rapid Gas Inflows in z ∼ 2 Star-forming Disks

We report high-quality Hα/CO imaging spectroscopy of nine massive (log median stellar mass = 10.65 M ⊙) disk galaxies on the star-forming main sequence (henceforth SFGs), near the peak of cosmic galaxy evolution (z ∼ 1.1–2.5), taken with the ESO Very Large Telescope, IRAM-NOEMA, and Atacama Large Millimeter/submillimeter Array. We fit the major axis position–velocity cuts with beam-convolved, forward models with a bulge, a turbulent rotating disk, and a dark matter (DM) halo. We include priors for stellar and molecular gas masses, optical light effective radii and inclinations, and DM masses from our previous rotation curve analysis of these galaxies. We then subtract the inferred 2D model-galaxy velocity and velocity dispersion maps from those of the observed galaxies. We investigate whether the residual velocity and velocity dispersion maps show indications for radial flows. We also carry out kinemetry, a model-independent tool for detecting radial flows. We find that all nine galaxies exhibit significant nontangential flows. In six SFGs, the inflow velocities (v r ∼ 30–90 km s−1, 10%–30% of the rotational component) are along the minor axis of these galaxies. In two cases the inflow appears to be off the minor axis. The magnitudes of the radial motions are in broad agreement with the expectations from analytic models of gravitationally unstable, gas-rich disks. Gravitational torques due to clump and bar formation, or spiral arms, drive gas rapidly inward and result in the formation of central disks and large bulges. If this interpretation is correct, our observations imply that gas is transported into the central regions on ∼10 dynamical timescales.

Resolved Kennicutt–Schmidt law in two strongly lensed star-forming galaxies at redshift 1

We study the star formation rate (SFR) vs. molecular gas mass (Mmol) scaling relation from hundreds to thousands of parsec in two strongly lensed galaxies at redshift z ∼ 1, the Cosmic Snake and A521. We trace the SFR using extinction-corrected rest-frame UV observations with the Hubble Space Telescope (HST), and Mmol using detections of the CO(4–3) line with the Atacama Large Millimeter/submillimeter Array (ALMA). The similar angular resolutions of our HST and ALMA observations of 0.15 − 0.2″ combined with magnifications reaching μ > 20 enable us to resolve structures in the galaxies of sizes lower than 100 pc. These resolutions are close to those of studies of nearby galaxies. This allows us to investigate for the first time the Kennicutt–Schmidt (KS) law (SFR–Mmol surface densities) at different spatial scales, from galactic scales to ∼100 pc scales, in galaxies at z ∼ 1. At integrated scales we find that both galaxies satisfy the KS law defined by galaxies at redshifts between 1 and 2.5. We test the resolved KS (rKS) law in cells of sizes down to 200 pc in the two galaxies. We observe that this relationship generally holds in these z ∼ 1 galaxies, although its scatter increases significantly with decreasing spatial scales. We check the scale dependence of the spatial correlation between the surface densities of SFR and Mmol by focusing on apertures centred on individual star-forming regions and molecular clouds. We conclude that star-forming regions and molecular clouds become spatially de-correlated at ≲1 kpc in the Cosmic Snake, whereas they appear de-correlated at all spatial scales (from 400 pc to 6 kpc) in A521.

The Gas Accretion Rate of Star-forming Galaxies over the Last 4 Gyr

Star-forming galaxies are believed to replenish their atomic gas reservoir, which is consumed in star formation, through accretion of gas from their circumgalactic mediums (CGMs). However, there are few observational constraints today on the gas accretion rate in external galaxies. Here, we use our recent measurement of the scaling relation between the atomic hydrogen (H i) mass M H I and the stellar mass M * in star-forming galaxies at z ≈ 0.35, with the relations between the star formation rate (SFR) and M *, and the molecular gas mass M Mol and M *, and the assumption that star-forming galaxies evolve along the main sequence, to determine the evolution of the neutral gas reservoir and the average net gas accretion rate onto the disks of star-forming galaxies over the past 4 Gyr. For galaxies with M * ≳ 109 M ⊙ today, we find that both M * and M H I in the disk have increased, while M Mol has decreased, since z ≈ 0.35. The average gas accretion rate onto the disk over the past 4 Gyr is similar to the average SFR over this period, implying that main-sequence galaxies have maintained a stable H i reservoir, despite the consumption of gas in star formation. We obtain an average net gas accretion rate (over the past 4 Gyr) of ≈6 M ⊙ yr−1 for galaxies with the stellar mass of the Milky Way. At low redshifts, z ≲ 0.4, the reason for the decline in the cosmic SFR density thus appears to be the inefficiency in the conversion of atomic gas to molecular gas, rather than insufficient gas accretion from the CGM.

Z-GAL: A NOEMA spectroscopic redshift survey of bright Herschel galaxies

The z-GAL survey observed 137 bright Herschel-selected targets with the IRAM Northern Extended Millimeter Array, with the aim to measure their redshift and study their properties. Several of them have been resolved into multiple sources. Consequently, robust spectroscopic redshifts have been measured for 165 individual galaxies in the range 0.8 < z < 6.5. In this paper we analyse the millimetre spectra of the z-GAL sources, using both their continuum and line emission to derive their physical properties. At least two spectral lines are detected for each source, including transitions of 12CO, [CI], and H2O. The observed 12CO line ratios and spectral line energy distributions of individual sources resemble those of local starbursts. In seven sources the para-H2O (211−202) transition is detected and follows the IR versus H2O luminosity relation of sub-millimetre galaxies. The molecular gas mass of the z-GAL sources is derived from their 12CO, [CI], and sub-millimetre dust continuum emission. The three tracers lead to consistent results, with the dust continuum showing the largest scatter when compared to 12CO. The gas-to-dust mass ratio of these sources was computed by combining the information derived from 12CO and the dust continuum and has a median value of 107, similar to star-forming galaxies of near-solar metallicity. The same combined analysis leads to depletion timescales in the range between 0.1 and 1.0 Gyr, which place the z-GAL sources between the ‘main sequence’ of star formation and the locus of starbursts. Finally, we derived a first estimate of stellar masses – modulo possible gravitational magnification – by inverting known gas scaling relations: the z-GAL sample is confirmed to be mostly composed by starbursts, whereas ∼25% of its members lie on the main sequence of star-forming galaxies (within ±0.5 dex).

Bright submillimeter galaxies do trace galaxy protoclusters

There is controversy in the literature regarding whether distant, massive, and dusty starbursts selected at (sub)millimeter wavelengths can trace galaxy overdensities. We thus performed the first systematic search for distant protoclusters around a homogeneously selected sample of 12 spectroscopically confirmed submillimeter galaxies (SMGs) at z ∼ 1.2 − 5.3, which we selected from the GOODS-N field. We applied the well-established Poisson probability method (PPM) to search for megaparsec-scale overdensities around these SMGs, using three different photometric redshift catalogs. We robustly detect galaxy overdensities for 11 out of the 12 SMGs (i.e., 92%±8%), distributed over eight large-scale protoclusters. We confirm all three previously discovered protoclusters, and we detect five new ones around the SMGs SMM J123634 (z = 1.225), ID.19 (z = 2.047), SMM J123607 (z = 2.487), SMM J123606 (z = 2.505), and GN10 (z = 5.303). A wavelet-based analysis of the protocluster fields shows that the SMGs are located in protocluster cores with a complex morphology (compact, filamentary, or clumpy) and an average size of ∼(0.4 − 1) Mpc. By comparing the PPM results obtained using the three redshift catalogs independently, each of which trace different galaxy populations and redshift ranges, we speculate that we are possibly witnessing a transitioning phase at z ≳ 4 for the galaxy population of protoclusters. While z ≲ 4 protoclusters appear to be populated by dusty galaxies, those at the highest redshifts, z ∼ 5, are detected as overdensities of Lyman α emitters or Lyman break galaxies. Further investigation with larger samples is required to reach a definitive conclusion. We also find a good correlation between the molecular (H2) gas mass of the SMGs and the significance of the associated overdensity. To explain the overall phenomenology, we suggest that galaxy interactions in dense environments likely triggered the starburst and gas-rich phase of the SMGs. Altogether, our findings support the scenario that SMGs are excellent tracers of distant protoclusters. The ones presented in this work are excellent targets for the James Webb Space Telescope. Similarly, future surveys with forthcoming facilities (e.g., Euclid and LSST) can be tuned to detect even larger samples of distant protoclusters.

The inefficiency of stellar feedback in driving galactic outflows in massive galaxies at high redshift

ABSTRACT Recent observations indicate that galactic outflows are ubiquitous in high-redshift (high-z) galaxies, including normal star-forming galaxies, quasar hosts, and dusty star-forming galaxies (DSFGs). However, the impact of outflows on the evolution of their hosts is still an open question. Here, we analyse the star-formation histories and galactic outflow properties of galaxies in massive haloes ($10^{12}\, {\rm M}_{\odot }\ \lt\ M_{\rm vir}\ \lt\ 5\times 10^{12}\, {\rm M}_{\odot }$) at z ≳ 5.5 in three zoom-in cosmological simulations from the MassiveFIRE suite, as part of the Feedback In Realistic Environments (FIRE) project. The simulations were run with the FIRE-2 model, which does not include feedback from active galactic nuclei. The simulated galaxies resemble z > 4 DSFGs, with star-formation rates of $\sim\!{1000}\ {\rm M}_{\odot }\, \rm yr^{-1}$ and molecular gas masses of Mmol ∼ 1010 M⊙. However, the simulated galaxies are characterized by higher circular velocities than those observed in high-z DSFGs. The mass loading factors from stellar feedback are of the order of ∼0.1, implying that stellar feedback is inefficient in driving galactic outflows and gas is consumed by star formation on much shorter time-scales than it is expelled from the interstellar medium. We also find that stellar feedback is highly inefficient in self-regulating star formation in this regime, with an average integrated star formation efficiency (SFE) per dynamical time of 30 per cent. Finally, compared with FIRE-2 galaxies hosted in similarly massive haloes at lower redshift, we find lower mass loading factors and higher SFEs in the high-z sample. We argue that both effects originate from the higher total and gas surface densities that characterize high-z massive systems.

Faint [C i](1–0) emission in z ∼ 3.5 radio galaxies

ABSTRACT We present Atacama Large Millimeter/sub-millimeter Array neutral carbon, [${\rm C\, \small {\rm I}}$](1–0), line observations that probe molecular hydrogen gas (H2) within seven radio galaxies at z = 2.9−4.5 surrounded by extended (≳100 kpc) Ly α nebulae. We extract [${\rm C\, \small {\rm I}}$](1–0) emission from the radio-active galactic nuclei (AGNs) host galaxies whose positions are set by near-infrared detections and radio detections of the cores. Additionally, we place constraints on the galaxies’ systemic redshifts via ${\rm He\, \small {\rm II}}$ λ1640 lines seen with the Multi-Unit Spectroscopic Explorer. We detect faint [${\rm C\, \small {\rm I}}$] emission in four out of seven sources. In two of these galaxies, we discover narrow-line emission of full width at half-maximum ≲100 km s−1 that may trace emission from bright kpc-scale gas clouds within the interstellar medium (ISM). In the other two [${\rm C\, \small {\rm I}}$]-detected galaxies, line dispersions range from ∼100−600 km s−1 and may be tracing the rotational component of the cold gas. Overall, the [${\rm C\, \small {\rm I}}$] line luminosities correspond to H2 masses of $M_{\rm H_2,[{\rm C\, \small {\rm I}}]} \simeq (0.5{\!-\!}3) \times 10^{10}$ M⊙ for the detections and $M_{\rm H_2,[{\rm C\, \small {\rm I}}]}\lt 0.65\times 10^{10}$ M⊙ for the [${\rm C\, \small {\rm I}}$] non-detections in three out of seven galaxies within the sample. The molecular gas masses in our sample are relatively low in comparison to previously reported measures for similar galaxies that are $M_{\rm H_2,[{\rm C\, \small {\rm I}}]} \simeq (3{\!-\!}4) \times 10^{10}$ M⊙. Our results imply that the observed faintness in carbon emission is representative of a decline in molecular gas supply from previous star formation epochs and/or a displacement of molecular gas from the ISM due to jet-powered outflows.

CO-CHANGES – I. IRAM 30-m CO observations of molecular gas in the sombrero galaxy

ABSTRACT Molecular gas plays a critical role in explaining the quiescence of star formation (SF) in massive isolated spiral galaxies, which could be a result of either the low molecular gas content and/or the low SF efficiency. We present IRAM 30-m observations of the CO lines in the Sombrero galaxy (NGC 4594), the most massive spiral at $d\lesssim 30\rm ~Mpc$. We detect at least one of the three CO lines covered by our observations in all 13 observed positions located at the galactic nucleus and along an $\sim 25\rm ~kpc$-diameter dusty ring. The total extrapolated molecular gas mass of the galaxy is $M_{\rm H_2}\approx 4\times 10^{8}\rm ~M_\odot$. The measured maximum CO gas rotation velocity of $\approx 381\rm ~km~s^{-1}$ suggests that NGC 4594 locates in a dark matter halo with a mass $M_{\rm 200}\gtrsim 10^{13}\rm ~M_\odot$. Comparing to other galaxy samples, NGC 4594 is extremely gas poor and SF inactive, but the SF efficiency is apparently not inconsistent with that predicted by the Kennicutt–Schmidt law, so there is no evidence of enhanced SF quenching in this extremely massive spiral with a huge bulge. We also calculate the predicted gas supply rate from various sources to replenish the cold gas consumed in SF, and find that the galaxy must experience a starburst stage at high redshift, then the leftover or recycled gas provides SF fuels to maintain the gradual growth of the galactic disc at a gentle rate.

The correlation between the 500 pc scale molecular gas masses and AGN powers for massive elliptical galaxies

Abstract Massive molecular clouds have been discovered in massive elliptical galaxies at the center of galaxy clusters. Some of this cold gas is expected to flow in the central supermassive black holes and activate galactic nucleus (AGN) feedback. In this study, we analyze archival Atacama Large Millimeter Array (ALMA) data of nine massive elliptical galaxies, focusing on CO line emissions, to explore the circumnuclear gas. We show that the mass of the molecular gas within a fixed radius (500 pc) from the AGNs (Mmol ∼ 107–108 M⊙) is correlated with the jet power estimated from X-ray cavities (Pcav ∼ 1042–1045 erg s−1). The mass accretion rate of the circumnuclear gas $\dot{M}$ also has a correlation with Pcav. On the other hand, the continuum luminosities at ∼1.4 GHz and ∼100–300 GHz have no correlation with Mmol. These results indicate that the circumnuclear gas is sustaining the long-term AGN activities (∼107 yr) rather than the current ones. The circumnuclear gas mass is a better indicator of the jet power than the continuum luminosity, which probably changes on a shorter time scale. We also study the origin of the continuum emission from the AGNs at ∼100–300 GHz and find that it is mostly synchrotron radiation. For low-luminosity AGNs, however, dust emission appears to contaminate the continuum.

Wide-field CO isotopologue emission and the CO-to-H2 factor across the nearby spiral galaxy M101

Carbon monoxide (CO) emission constitutes the most widely used tracer of the bulk molecular gas in the interstellar medium (ISM) in extragalactic studies. The CO-to-H2 conversion factor, α12CO(1−0), links the observed CO emission to the total molecular gas mass. However, no single prescription perfectly describes the variation of α12CO(1−0) across all environments within and across galaxies as a function of metallicity, molecular gas opacity, line excitation, and other factors. Using spectral line observations of CO and its isotopologues mapped across a nearby galaxy, we can constrain the molecular gas conditions and link them to a variation in α12CO(1−0). Here, we present new, wide-field (10 × 10 arcmin2) IRAM 30-m telescope 1 mm and 3 mm line observations of 12CO, 13CO, and C18O across the nearby, grand-design, spiral galaxy M101. From the CO isotopologue line ratio analysis alone, we find that selective nucleosynthesis and changes in the opacity are the main drivers of the variation in the line emission across the galaxy. In a further analysis step, we estimated α12CO(1−0) using different approaches, including (i) via the dust mass surface density derived from far-IR emission as an independent tracer of the total gas surface density and (ii) local thermal equilibrium (LTE) based measurements using the optically thin 13CO(1–0) intensity. We find an average value of ⟨α12CO(1 − 0)⟩ = 4.4 ± 0.9 M⊙ pc−2 (K km s−1)−1 across the disk of the galaxy, with a decrease by a factor of 10 toward the 2 kpc central region. In contrast, we find LTE-based α12CO(1−0) values are lower by a factor of 2–3 across the disk relative to the dust-based result. Accounting for α12CO(1−0) variations, we found significantly reduced molecular gas depletion time by a factor 10 in the galaxy’s center. In conclusion, our result suggests implications for commonly derived scaling relations, such as an underestimation of the slope of the Kennicutt Schmidt law, if α12CO(1−0) variations are not accounted for.

First Results from the JWST Early Release Science Program Q3D: The Warm Ionized Gas Outflow in z ∼ 1.6 Quasar XID 2028 and Its Impact on the Host Galaxy

Quasar feedback may regulate the growth of supermassive black holes, quench coeval star formation, and impact galaxy morphology and the circumgalactic medium. However, direct evidence for quasar feedback in action at the epoch of peak black hole accretion at z ≈ 2 remains elusive. A good case in point is the z = 1.6 quasar WISEA J100211.29+013706.7 (XID 2028), where past analyses of the same ground-based data have come to different conclusions. Here, we revisit this object with the integral-field unit of the Near Infrared Spectrograph on board the JWST as part of Early Release Science program Q3D. The excellent angular resolution and sensitivity of the JWST data reveal new morphological and kinematic substructures in the outflowing gas plume. An analysis of the emission-line ratios indicates that photoionization by the central quasar dominates the ionization state of the gas with no obvious sign for a major contribution from hot young stars anywhere in the host galaxy. The rest-frame near-UV emission aligned along the wide-angle cone of outflowing gas is interpreted as a scattering cone. The outflow has cleared a channel in the dusty host galaxy, through which some of the quasar ionizing radiation is able to escape and heat the surrounding interstellar and circumgalactic media. Although the warm ionized outflow is not powerful enough to impact the host galaxy via mechanical feedback, radiative feedback by the active galactic nucleus, aided by the outflow, may help to explain the unusually small molecular gas mass fraction in the galaxy host.

Rapid Growth of Galactic Supermassive Black Holes through Accreting Giant Molecular Clouds during Major Mergers of Their Host Galaxies

Understanding the formation of the supermassive black holes (SMBHs) present in the centers of galaxies is a crucial topic in modern astrophysics. Observations have detected SMBHs with masses of 109 M ⊙ in the high-redshift galaxies with z ∼ 7. However, how SMBHs grew to such huge masses within the first billion years after the Big Bang remains elusive. One possible explanation is that SMBHs grow quickly through the frequent mergers of galaxies, which provides sustainable gas to maintain rapid growth. This study presents the hydrodynamics simulations of the SMBHs’ growth with their host galaxies using the GIZMO code. In contrast to previous simulations, we have developed a giant molecular cloud (GMC) model by separating molecular gas particles from atomic gas particles and then evolving them independently. During major mergers, we show that the more massive molecular gas particles’ cloud bears stronger dynamical friction. Consequently, GMCs are substantially accreted onto the galactic centers that grow SMBHs from ∼107 to ∼109 M ⊙ within 300 Myr, which explains the rapid growth of SMBHs, and this accretion also triggers a violent starburst at the galactic center. Furthermore, we examine the impact of minor mergers on the bulge of a Milky Way–like galaxy and find that the size and mass of the bulge can increase from 0.92 to 1.9 kpc and from 4.7 × 1010 to 7 × 1010 M ⊙.

Big Three Dragons: Molecular Gas in a Bright Lyman-break Galaxy at z = 7.15

We report Atacama Large Millimeter/submillimeter Array Band 3 observations of CO(6−5), CO(7−6), and [C i](2−1) in B14-65666 (“Big Three Dragons”), one of the brightest Lyman-break galaxies at z > 7 in the rest-frame ultraviolet continuum, far-infrared continuum, and emission lines of [O iii] 88 μm and [C ii] 158 μm. CO(6−5), CO(7−6), and [C i](2−1), whose 3σ upper limits on the luminosities are approximately 40 times fainter than the [C ii] luminosity, are all not detected. The L [C II]/L CO(6–5) and L [C II]/L CO(7–6) ratios are higher than the typical ratios obtained in dusty star-forming galaxies or quasar host galaxies at similar redshifts, and they may suggest a lower gas density in the photodissociated region in B14-65666. By using the (1) [C ii] luminosity, (2) dust mass-to-gas mass ratio, and (3) a dynamical mass estimate, we find that the molecular gas mass (M mol) is (0.05–11) × 1010 M ⊙. This value is consistent with the upper limit inferred from the nondetection of mid-J CO and [C i](2−1). Despite the large uncertainty in M mol, we estimate a molecular gas-to-stellar mass ratio (μ gas) of 0.65–140 and a gas depletion time (τ dep) of 2.5–550 Myr; these values are broadly consistent with those of other high-redshift galaxies. B14-65666 could be an ancestor of a passive galaxy at z ≳ 4 if no gas is fueled from outside the galaxy.

The Dragonfly Galaxy. III. Jet Brightening of a High-redshift Radio Source Caught in a Violent Merger of Disk Galaxies

The Dragonfly galaxy (MRC 0152-209), the most infrared-luminous radio galaxy at redshift z ∼ 2, is a merger system containing a powerful radio source and large displacements of gas. We present kiloparsec-resolution data from the Atacama Large Millimeter/submillimeter Array and the Very Large Array of carbon monoxide (6−5), dust, and synchrotron continuum, combined with Keck integral field spectroscopy. We find that the Dragonfly consists of two galaxies with rotating disks that are in the early phase of merging. The radio jet originates from the northern galaxy and brightens when it hits the disk of the southern galaxy. The Dragonfly galaxy therefore likely appears as a powerful radio galaxy because its flux is boosted into the regime of high-z radio galaxies by the jet–disk interaction. We also find a molecular outflow of (1100 ± 550) M ⊙ yr−1 associated with the radio host galaxy, but not with the radio hot spot or southern galaxy, which is the galaxy that hosts the bulk of the star formation. Gravitational effects of the merger drive a slower and longer-lived mass displacement at a rate of (170 ± 40) M ⊙ yr−1, but this tidal debris contains at least as much molecular gas mass as the much faster outflow, namely M H2 = (3 ± 1) × 109 (α CO/0.8) M ⊙. This suggests that both the active-galactic-nucleus-driven outflow and mass transfer due to tidal effects are important in the evolution of the Dragonfly system. The Keck data show Lyα emission spread across 100 kpc, and C iv and He ii emission across 35 kpc, confirming the presence of a metal-rich and extended circumgalactic medium previously detected in CO(1–0).