Outflow Of Molecular Gas Research Articles

Active Galactic Nuclei and Star Formation in nearby Galaxies (AGNSTRONG). I. Sample and Strategy

We introduce our project, AGNSTRONG (Active Galactic Nuclei and STaR fOrmation in Nearby Galaxies). Our research goals encompass investigating the kinematic properties of ionized and molecular gas outflows, understanding the impact of AGN feedback, and exploring the coevolution dynamics between AGN strength activity and star formation activity. We aim to conduct a thorough analysis to determine whether there is an increase or suppression in star formation rates (SFRs) among targets with and without powerful relativistic jets. Our sample consists of 35 nearby AGNs with and without powerful relativistic jet detections. Utilizing submillimeter continuum observations at 450 and 850 μm from SCUBA-2 at the James Clerk Maxwell Telescope, we determine SFRs for our sources using spectral energy distribution (SED) fitting models. Additionally, we employ high-quality, spatially resolved spectra from UV-optical to near-infrared bands obtained with the Double Spectrograph and Triple Spectrograph mounted on the 200 inch Hale Telescope at Palomar Observatory to study their multiphase gas outflow properties. This paper presents an overview of our sample selection methodology, research strategy, and initial results of our project. We find that the SFRs determined without including the submillimeter data in the SED fitting are overestimated by ∼0.08 dex compared to those estimated with the inclusion of submillimeter data. Additionally, we compare the estimated SFRs in our work with those traced by the 4000 Å break, as provided by the Max Planck Institute for Astrophysics and Johns Hopkins University catalog. We find that our determined SFRs are systematically higher than those traced by the 4000 Å break. Finally, we outline our future research plans.

On the Evidence for Molecular Outflows in High-redshift Dusty Star-forming Galaxies

Galactic-scale outflows of molecular gas from star-forming galaxies constitute the most direct evidence for the regulation of star formation. In the early Universe (z > 4), such outflows have recently been inferred from gravitationally lensed dusty star-forming galaxies (DSFGs) based on ubiquitous detections of OH absorption extending to more blueshifted velocities than [C ii] or CO emission in spatially integrated spectra. Because these lines are redshifted to submillimeter wavelengths, such measurements require careful corrections for atmospheric absorption lines, and a proper accounting of sometimes large variations in measurement uncertainties over these lines. Taking these factors into consideration, we reanalyze OH and [C ii] data taken with the Atacama Large Millimeter/submillimeter Array for five sources where such data are available, of which four were categorised as exhibiting outflows. Based on their spatially integrated spectra alone, we find statistically significant (≥3σ) OH absorption more blueshifted than [C ii] emission in only one source. By contrast, searching channel maps for signals diluted below the detection threshold in spatially integrated spectra, we find evidence for a separate kinematic component in OH absorption in all five sources in the form of (i) more blueshifted OH absorption than [C ii] emission and/or (ii) a component in OH absorption exhibiting a different spatio-kinematic pattern than in [C ii] emission, the latter presumably tracing gas in a rotating disk. Providing a more complete and accurate assessment of molecular outflows in gravitationally lensed DSFGs, we suggest methods to assess the precision of corrections for atmospheric absorption better and to measure the source continuum in future observations more accurately.

The disk of the eruptive protostar V900 Mon

Aims. In this work, we study the silicate dust content in the disk of one of the youngest eruptive stars, V900 Mon, at the highest angular resolution, probing down to the inner 10 au of said disk, and study the historical evolution of the system, traced in part by a newly discovered emission clump. Methods. We performed high angular resolution MIR interferometric observations of V900 Mon with MATISSE/VLTI with a spatial coverage ranging from 38 to 130-m baselines, and compared them to archival MIDI/VLTI data. We also mined and re-analyzed archival optical and infrared photometry of the star to study its long-term evolution since its eruption in the 1990s. We complemented our findings with integral field spectroscopy data from MUSE/VLT. Results. The MATISSE/VLTI data suggest a radial variation in the silicate feature in the dusty disk, whereby at large spatial scales (≥10 au) the protostellar disk’s emission is dominated by large-sized (≥1μm) silicate grains, while at smaller spatial scales and closer to the star (≤5 au) silicate emission is absent, suggesting self-shielding. We propose that the self-shielding may be the result of small dust grains at the base of the collimated CO outflow previously detected by ALMA. A newly discovered knot in the MUSE/VLT data, located at a projected distance approximately 27 000 au from the star, is co-aligned with the molecular gas outflow at a P.A. of 250°(±5°) consistent with the position angle and inclination of the disk. The knot is seen in emission in Hα [N II], and the [S II] doublet and its kinematic age is about 5150 yr. This ejected material could originate from a previous eruption.

Radio jets in NGC 1068 with e-MERLIN and VLA: structure and morphology

ABSTRACT We present new high-sensitivity e-MERLIN and Very Large Array (VLA) radio images of the prototypical Seyfert 2 galaxy NGC 1068 at 5, 10, and 21 GHz. We image the radio jet, from the compact components north-east (NE), C, S1, and S2 to the faint double-lobed jet structure of the NE and south-west (SW) jet lobes. We map the jet between 15 kλ and 3300 kλ spatial scales by combining enhanced-Multi Element Radio Linked Interferometer Network (e-MERLIN) and VLA data for the first time. Components NE, C, and S2 have steep spectra indicative of optically thin non-thermal emission domination between 5 and 21 GHz. Component S1, which is where the active galactic nucleus resides, has a flat radio spectrum. We report a new component, S2a, a part of the southern jet. We compare these new data with the MERLIN and VLA data observed in 1983, 1992, and 1995 and report a flux decrease by a factor of 2 in component C, suggesting variability of this jet component. With the high angular resolution e-MERLIN maps, we detect the bow shocks in the NE jet lobe that coincide with the molecular gas outflows observed with ALMA. The NE jet lobe has a jet power of $P_{\rm jet-NElobe}\, =\,$ 6.7 × 1042 erg s−1 and is considered to be responsible for driving out the dense molecular gas observed with ALMA around the same region.

The AGNIFS survey: spatially resolved observations of hot molecular and ionized outflows in nearby active galaxies

ABSTRACTWe present the hot molecular and warm ionized gas kinematics for 33 nearby (0.001 ≲ z ≲ 0.056) X-ray selected active galaxies using the H$_2\, 2.1218\, \mu$m and Br γ emission lines observed in the K band with the Gemini near-infrared integral field spectrograph. The observations cover the inner 0.04–2 kpc of each active galactic nucleus at spatial resolutions of 4–250 pc with a velocity resolution of σinst ≈ 20 ${\rm km\, s^{-1}}$. We find that 31 objects (94 per cent) present a kinematically disturbed region (KDR) seen in ionized gas, while such regions are observed in hot molecular gas for 25 galaxies (76 per cent). We interpret the KDR as being due to outflows with masses of 102–107 and 100–104 M⊙ for the ionized and hot molecular gas, respectively. The ranges of mass-outflow rates ($\dot{M}_{\rm out}$) and kinetic power ($\dot{E}_{\rm K}$) of the outflows are 10−3–101 M⊙ yr−1 and ∼1037–1043 erg s−1 for the ionized gas outflows, and 10−5–10−2 M⊙ yr−1 and 1035–1039 erg s−1 for the hot molecular gas outflows. The median coupling efficiency in our sample is $\dot{E}_{\mathrm{K}}/L_{\rm bol}\approx 1.8\times 10^{-3}$ and the estimated momentum fluxes of the outflows suggest they are produced by radiation-pressure in low-density environment, with possible contribution from shocks.

Building Options for the Brazilian Pre-salt: A technical-economic and infrastructure analysis of offshore integration between energy generation and natural gas exploration

The objective of this work is to evaluate the technical-economic and infrastructure aspects for the Brazilian Pre-salt natural gas use. Factors like technology maturity level, fuel and facilities costs, and electricity market are analyzed; the levelized cost of energy (LCOE) of two possibilities are calculated: (i) offshore Gas-to-Wire (GtW) and (ii) molecular natural gas outflow through the pipeline with onshore thermoelectric generation. This work also discusses the possibility of natural gas (NG) transport via liquefaction, considering the Floating Liquefied NG (FLNG) technology for national and international market. The LCOE of GtW technology is higher (67–87 US$/MWh) than onshore plants (43–69 US$/MWh) for Pre-salt area, higher than the historical energy price of Brazilian NG thermoelectric generation (44 US$/MWh), but, in general, lower than Brazilian NG energy auction price cap (84.5 US$/MWh) and lower than some values found in the literature for onshore plants (42–124 US$/MWh) abroad Brazil. FLNG technology is still new, there is no scale, few players use it, and it does not seem to be a feasible option for Pre-salt NG now. It is concluded that elements such as political uncertainties of the international natural gas market, the high CO2 rate in the Pre-salt's natural gas mixture, and the difficulties in implement deep-sea infrastructure are challenging elements for the three possibilities analyzed. The Brazilian market discussion is relevant since it is a greenfield natural gas area in need of development. Thus, it is of upmost importance to implement a comprehensive energy policy to address offshore-onshore energy integration regulation and technological developments for the offshore transmission systems, and CO2 content separation process.

Evidence of extended cold molecular gas and dust haloes around z ~ 2.3 extremely red quasars with ALMA

ABSTRACT Large-scale outflows are believed to be an important mechanism in the evolution of galaxies. We can determine the impact of these outflows by studying either current galaxy outflows and their effect in the galaxy or by studying the effect of past outflows on the gas surrounding the galaxy. In this work, we examine the CO(7−6), [C i] ($^{3} \rm P_{1} \rightarrow {\rm ^3 P}_{0}$), H2O 211–202, and dust continuum emission of 15 extremely red quasars at z ∼ 2.3 using ALMA. By investigating the radial surface brightness profiles of both the individual sources and the stacked emission, we detect extended cold gas and dust emission on scales of ∼14 kpc in CO(7−6), [C i](2−1), and dust continuum. This is the first time that the presence of a large amount of molecular gas was detected on large, circumgalactic medium scales around quasar host galaxies using [C i] extended emission. We estimate the dust and molecular gas mass of these haloes to be 107.6 and 1010.6 M⊙, indicating significant dust and molecular gas reservoirs around these extreme quasars. By estimating the time-scale at which this gas can reach these distances by molecular gas outflows (7–32 Myr), we conclude that these haloes are a relic of past AGN or starburst activity, rather than an effect of the current episode of extreme quasar activity.

The State of the Molecular Gas in Post-starburst Galaxies

The molecular gas in galaxies traces both the fuel for star formation and the processes that can enhance or suppress star formation. Observations of the molecular gas state can thus point to when and why galaxies stop forming stars. In this study, we present Atacama Large Millimeter/submillimeter Array observations of the molecular gas in galaxies evolving through the post-starburst phase. These galaxies have low current star formation rates (SFRs), regardless of the SFR tracer used, with recent starbursts ending within the last 600 Myr. We present CO (3–2) observations for three post-starburst galaxies, and dense gas HCN/HCO+/HNC (1–0) observations for six (four new) post-starburst galaxies. The post-starbursts have low excitation traced by the CO spectral-line energy distribution up to CO (3–2), more similar to early-type than starburst galaxies. The low excitation indicates that lower density rather than high temperatures may suppress star formation during the post-starburst phase. One galaxy displays a blueshifted outflow traced by CO (3–2). MaNGA observations show that the ionized gas velocity is disturbed relative to the stellar velocity field, with a blueshifted component aligned with the molecular gas outflow, suggestive of a multiphase outflow. Low ratios of HCO+/CO, indicating low fractions of dense molecular gas relative to the total molecular gas, are seen throughout post-starburst phase, except for the youngest post-starburst galaxy considered here. These observations indicate that the impact of any feedback or quenching processes may be limited to low excitation and weak outflows in the cold molecular gas during the post-starburst phase.

Role of Magnetic Fields in Fueling Seyfert Nuclei

Molecular gas is believed to be the fuel for star formation and nuclear activity in Seyfert galaxies. To explore the role of magnetic fields in funneling molecular gas into the nuclear region, measurements of the magnetic fields embedded in molecular gas are needed. By applying the new velocity gradient technique (VGT) to CO isotopolog data from the Atacama Large Millimeter/submillimeter Array and the Plateau de Bure Interferometer Arcsecond Whirlpool Survey, we obtain the first detection of CO-associated magnetic fields in several nearby Seyfert galaxies and their unprecedented high-resolution magnetic field maps. The VGT-measured magnetic fields in molecular gas globally agree with those inferred from existing HAWC+ dust polarization and Very Large Array synchrotron polarization. An overall good alignment between the magnetic fields traced by VGT-CO and by synchrotron polarization may support the correlation between star formation and cosmic-ray generation. We find that the magnetic fields traced by VGT-CO have a significant radial component in the central regions of most Seyferts in our sample, where efficient molecular gas inflows or outflow may occur. In particular, we find local misalignment between the magnetic fields traced by CO and dust polarization within the nuclear ring of NGC 1097, and the former aligns with the central bar’s orientation. This misalignment reveals different magnetic field configurations in different gas phases and may provide an observational diagnostic for the ongoing multiphase fueling of Seyfert activity.

Properties of cold molecular gas in four type-1 active galaxies hosting outflows

ABSTRACT Feedback from active galactic nuclei (AGN) has proven to be a critical ingredient in the current picture of galaxy assembly and growth. However, observational constraints on AGN-driven outflows face technical challenges and as a result, the cold molecular gas outflow properties of type-1 AGN are not well known. We present new IRAM NOrthern Extended Millimeter Array observations of CO$\, (1{-}0)$ in F07599+6508, Z11598 − 0112, F13342 + 3932, and PG1440 + 356, all nearby type-1 AGN and ultraluminous infrared galaxies. We achieve spatial resolution of 1–3 arcsec corresponding to physical scales of 2–8 kpc and spectral resolution of 15–60 km s−1, which enables updated CO$\, (1{-}0)$ redshifts and a detailed morphological view of the cold molecular gas in these sources. The CO$\, (1{-}0)$ luminosities, $L_{CO}^{\prime }$, are in the range 2–12 × 109 K km s−1 pc2 and inferred molecular gas masses, M(H2), are in the range 2–9 × 109 M⊙. The velocity fields and gas distributions do not unambiguously identify any of these sources as having outflows. However, Z11598 − 0112 has signs of infalling material and after the subtraction of a rotating disc model PG 1440 + 356 shows complex kinematics in the residuals that may indicate an outflow or warped disc.

Ubiquitous Molecular Outflows in z > 4 Massive, Dusty Galaxies. II. Momentum-driven Winds Powered by Star Formation in the Early Universe

Abstract Galactic outflows of molecular gas are a common occurrence in galaxies and may represent a mechanism by which galaxies self-regulate their growth, redistributing gas that could otherwise have formed stars. We previously presented the first survey of molecular outflows at z > 4 toward a sample of massive, dusty galaxies. Here we characterize the physical properties of the molecular outflows discovered in our survey. Using low-redshift outflows as a training set, we find agreement at the factor of 2 level between several outflow rate estimates. We find molecular outflow rates of 150–800 yr−1 and infer mass loading factors just below unity. Among the high-redshift sources, the molecular mass loading factor shows no strong correlations with any other measured quantity. The outflow energetics are consistent with expectations for momentum-driven winds with star formation as the driving source, with no need for energy-conserving phases. There is no evidence for active galactic nucleus activity in our sample, and while we cannot rule out deeply buried active galactic nuclei, their presence is not required to explain the outflow energetics, in contrast to nearby obscured galaxies with fast outflows. The fraction of the outflowing gas that will escape into the circumgalactic medium (CGM), though highly uncertain, may be as high as 50%. This nevertheless constitutes only a small fraction of the total cool CGM mass based on a comparison to z ∼ 2–3 quasar absorption line studies, but could represent ≳10% of the CGM metal mass. Our survey offers the first statistical characterization of molecular outflow properties in the very early universe.

Searching for molecular gas inflows and outflows in the nuclear regions of five Seyfert galaxies

Active galactic nucleus (AGN) driven outflows are believed to play an important role in regulating the growth of galaxies, mostly via negative feedback. However, their effects on their hosts are far from clear, especially for low- and moderate-luminosity Seyferts. To investigate this issue, we obtained cold molecular gas observations, traced by the CO(2-1) transition, using the NOEMA interferometer of five nearby (distances between 19 and 58 Mpc) Seyfert galaxies. The resolution of ∼0.3–0.8 (∼30–100 pc) and field of view of NOEMA allowed us to study the CO(2-1) morphology and kinematics in the nuclear regions (∼100 pc) and up to radial distances of ∼900 pc. We detected CO(2-1) emission in all five galaxies with disky or circumnuclear ring-like morphologies. We derived cold molecular gas masses on nuclear (∼100 pc) and circumnuclear (∼650 pc) scales in the range from 106 to 107 M⊙ and from 107 to 108 M⊙, respectively. In all of our galaxies, the bulk of this gas is rotating in the plane of the galaxy. However, noncircular motions are also present. In NGC 4253, NGC 4388, and NGC 7465, we can ascribe the streaming motions to the presence of a large-scale bar. In Mrk 1066 and NGC 4388, the noncircular motions in the nuclear regions are explained as outflowing material due to the interaction of the AGN wind with molecular gas in the galaxy disk. We conclude that for an unambiguous and precise interpretation of the kinematics of the cold molecular gas, we need detailed knowledge of the host galaxy (i.e., presence of bars, interactions, etc.), and also of the ionized gas kinematics and ionization cone geometry.

Molecular gas inflows and outflows in ultraluminous infrared galaxies at z ∼ 0.2 and one QSO at z = 6.1

Aims. Our aim is to search for and characterize inflows and outflows of molecular gas in four ultraluminous infrared galaxies (ULIRGs; LIR > 1012L⊙) at z ∼ 0.2−0.3 and one distant quasi-stellar object (QSO) at z = 6.13. Methods. We used Herschel/PACS and ALMA Band 7 observations of the hydroxyl molecule (OH) line at rest-frame wavelength 119 μm, which in absorption can provide unambiguous evidence of inflows or outflows of molecular gas in nuclear regions of galaxies. Our study contributes to doubling the number of OH 119 μm observations of luminous systems at z ∼ 0.2−0.3, and pushes the search for molecular outflows based on the OH 119 μm transition to z ∼ 6. Results. We detect OH 119 μm high-velocity absorption wings in three of the four ULIRGs. In two cases, IRAS F20036−1547 and IRAS F13352+6402, the blueshifted absorption profiles indicate the presence of powerful and fast (∼200−500 km s−1) molecular gas outflows. Consistent with an inside-out quenching scenario, these outflows are depleting the central reservoir of star-forming molecular gas at a rate similar to that of intense star formation activity. For the starburst-dominated system IRAS 10091+4704, we detect an inverted P Cygni profile that is unique among ULIRGs and indicates the presence of a fast (∼400 km s−1) inflow of molecular gas at a rate of ∼100 M⊙ yr−1 towards the central region. Finally, we tentatively detect (∼3σ) the OH 119 μm doublet in absorption in the z = 6.13 QSO ULAS J131911+095051. The OH 119 μm feature is blueshifted with a median velocity that suggests the presence of a molecular outflow, although characterized by a modest molecular mass loss rate of ∼200 M⊙ yr−1. This value is comparable to the small mass outflow rates found in the stacking of the [C II] spectra of other z ∼ 6 QSOs and suggests that ejective feedback in this phase of the evolution of ULAS J131911+095051 has subsided.

ALMA observations of PKS 1549–79: a case of feeding and feedback in a young radio quasar

We present CO(1−0) and CO(3−2) Atacama Large Millimeter/submillimeter Array observations of the molecular gas in PKS 1549−79, as well as mm and very long baseline interferometry 2.3-GHz continuum observations of its radio jet. PKS 1549−79 is one of the closest young, radio-loud quasars caught in an on-going merger in which the active galactic nucleus (AGN) is in the first phases of its evolution. We detect three structures tracing the accretion and the outflow of molecular gas: kpc-scale tails of gas accreting onto PKS 1549−79 from a merger, a circumnuclear disc in the inner few hundred parsec, and a very broad (> 2300 km s−1) component detected in CO(1−0) at the position of the AGN. Thus, in PKS 1549−79 we see the co-existence of accretion and the ejection of gas. The line ratio CO(3−2)/CO(1−0) suggests that the gas in the circumnuclear-disc has both high densities and high kinetic temperatures. We estimate a mass outflow rate of at least 650 M⊙ yr−1. This massive outflow is confined to the inner region (r < 120 pc) of the galaxy, which suggests that the AGN drives the outflow. Considering the amount of molecular gas available in the central nuclear disc and the observed outflow rate, we estimate a time scale of ∼105 yr over which the AGN would be able to destroy the circumnuclear disc, although gas from the merger may come in from larger radii, rebuilding this disc at the same time. The AGN appears to self-regulate gas accretion to the centre and onto the super-massive black hole. Surprisingly, from a comparison with Hubble Space Telescope data, we find that the ionised gas outflow is more extended. Nevertheless, the warm outflow is about two orders of magnitude less massive than the molecular outflow. PKS 1549−79 does not seem to follow the scaling relation between bolometric luminosity and the relative importance of warm ionised and molecular outflows claimed to exist for other AGN. We argue that, although PKS 1549−79 hosts a powerful quasar nucleus and an ultra-fast outflow, the radio jet plays a significant role in producing the outflow, which creates a cocoon of disturbed gas that expands into the circumnuclear disc.

The ALMA Discovery of the Rotating Disk and Fast Outflow of Cold Molecular Gas in NGC 1275

Abstract We present observations using the Atacama Large Millimeter/submillimeter Array of the CO(2−1), HCN(3−2), and HCO+(3−2) lines in the nearby radio galaxy/brightest cluster galaxy (BCG) NGC 1275 with a spatial resolution of ∼20 pc. In previous observations, the CO(2−1) emission was detected as radial filaments lying in the east–west direction on a kiloparsec scale. We resolved the inner filament and found that it cannot be represented by a simple infalling stream on a sub-kiloparsec scale. The observed complex nature of the filament resembles the cold gas structure predicted by numerical simulations of cold chaotic accretion. Within the central 100 pc, we detected a rotational disk of molecular gas whose mass is ∼108 M ⊙. This is the first evidence of the presence of a massive cold gas disk on this spatial scale for BCGs. A crude estimate suggests that the accretion rate of the cold gas can be higher than that of hot gas. The disk rotation axis is approximately consistent with the radio-jet axis. This probably suggests that the cold gas disk is physically connected to the innermost accretion disk, which is responsible for jet launching. We also detected absorption features in the HCN(3−2) and HCO+(3−2) spectra against the radio continuum emission mostly radiated by a jet of size ∼1.2 pc. The absorption features are blueshifted from the systemic velocity by ∼300–600 km s−1, suggesting the presence of outflowing gas from the active galactic nucleus (AGN). We discuss the relation of the AGN feeding with cold accretion, the origin of blueshifted absorption, and an estimate of the black hole mass using molecular gas dynamics.

Early Science with the Large Millimeter Telescope: An Energy-driven Wind Revealed by Massive Molecular and Fast X-Ray Outflows in the Seyfert Galaxy IRAS 17020+4544

Abstract We report on the coexistence of powerful gas outflows observed in millimeter and X-ray data of the radio-loud narrow-line Seyfert 1 Galaxy IRAS 17020+4544. Thanks to the large collecting power of the Large Millimeter Telescope (LMT), a prominent line arising from the 12CO(1–0) transition was revealed in recent observations of this source. The complex profile is composed by a narrow double-peak line and a broad wing. While the double-peak structure may be arising in a disk of molecular material, the broad wing is interpreted as the signature of a massive outflow of molecular gas with an approximate bulk velocity of −660 km s−1. This molecular wind is likely associated to a multi-component X-ray ultra-fast outflow with velocities reaching up to ∼ 0.1c and column densities in the range 1021–23.9 cm−2 that was reported in the source prior to the LMT observations. The momentum load estimated in the two gas phases indicates that within the observational uncertainties the outflow is consistent with being propagating through the galaxy and sweeping up the gas while conserving its energy. This scenario, which has been often postulated as a viable mechanism of how active galactic nucleus (AGN) feedback takes place, has so far been observed only in ultraluminous infrared galaxy sources. IRAS 17020+4544 with bolometric and infrared luminosity, respectively, of 5 × 1044 erg s−1 and 1.05 × 1011 L ⊙ appears to be an example of AGN feedback in a NLSy1 Galaxy (a low power AGN). New proprietary multi-wavelength data recently obtained on this source will allow us to corroborate the proposed hypothesis.

Molecular gas ejected from a distant galaxy

Galaxy Feedback Galaxies grow by forming stars from cold molecular gas. The rate at which they do so is limited by various feedback processes (such as supernovae or stellar winds) that heat and/or eject gas from the host galaxy. Spilker et al. used submillimeter observations to discover an outflow of molecular gas from a galaxy in the early Universe, a period of vigorous star formation. Modeling the outflow revealed that the mass of gas being ejected is similar to that being turned into stars. The results will help determine how quickly galaxies formed after the Big Bang. Science , this issue p. [1016][1] [1]: /lookup/doi/10.1126/science.aap8900

Fast molecular outflow from a dusty star-forming galaxy in the early Universe.

Galaxies grow inefficiently, with only a small percentage of the available gas converted into stars each free-fall time. Feedback processes, such as outflowing winds driven by radiation pressure, supernovae, or supermassive black hole accretion, can act to halt star formation if they heat or expel the gas supply. We report a molecular outflow launched from a dust-rich star-forming galaxy at redshift 5.3, 1 billion years after the Big Bang. The outflow reaches velocities up to 800 kilometers per second relative to the galaxy, is resolved into multiple clumps, and carries mass at a rate within a factor of 2 of the star formation rate. Our results show that molecular outflows can remove a large fraction of the gas available for star formation from galaxies at high redshift.

Spatially resolved cold molecular outflows in ULIRGs

We present new CO(2–1) observations of three low-z (d ~350 Mpc) ultra-luminous infrared galaxy (ULIRG) systems (six nuclei) observed with the Atacama large millimeter/submillimeter array (ALMA) at high spatial resolution (~500 pc). We detect massive cold molecular gas outflows in five out of six nuclei (Mout ~ (0.3−5) × 108 M⊙). These outflows are spatially resolved with deprojected effective radii between 250 pc and 1 kpc although high-velocity molecular gas is detected up to Rmax ~ 0.5−1.8 kpc (1–6 kpc deprojected). The mass outflow rates are 12–400 M⊙ yr−1 and the inclination corrected average velocity of the outflowing gas is 350–550 km s−1 (vmax = 500−900 km s−1). The origin of these outflows can be explained by the strong nuclear starbursts although the contribution of an obscured active galactic nucleus cannot be completely ruled out. The position angle (PA) of the outflowing gas along the kinematic minor axis of the nuclear molecular disk suggests that the outflow axis is perpendicular to the disk for three of these outflows. Only in one case is the outflow PA clearly not along the kinematic minor axis, which might indicate a different outflow geometry. The outflow depletion times are 15–80 Myr. These are comparable to, although slightly shorter than, the star-formation (SF) depletion times (30–80 Myr). However, we estimate that only 15–30% of the outflowing molecular gas will escape the gravitational potential of the nucleus. The majority of the outflowing gas will return to the disk after 5–10 Myr and become available to form new stars. Therefore, these outflows will not likely completely quench the nuclear starbursts. These star-forming powered molecular outflows would be consistent with being driven by radiation pressure from young stars (i.e., momentum-driven) only if the coupling between radiation and dust increases with increasing SF rates. This can be achieved if the dust optical depth is higher in objects with higher SF. This is the case in at least one of the studied objects. Alternatively, if the outflows are mainly driven by supernovae (SNe), the coupling efficiency between the interstellar medium and SNe must increase with increasing SF levels. The relatively small sizes (<1 kpc) and dynamical times (<3 Myr) of the cold molecular outflows suggests that molecular gas cannot survive longer in the outflow environment or that it cannot form efficiently beyond these distances or times. In addition, the ionized and hot molecular phases have been detected for several of these outflows, so this suggests that outflowing gas can experience phase changes and indicates that the outflowing gas is intrinsically multiphase, likely sharing similar kinematics, but different mass and, therefore, different energy and momentum contributions.

New places and phases of CO-poor/C i-rich molecular gas in the Universe

In this work we extend the work on the recently discovered role of Cosmic Rays (CRs) in regulating the average CO/$\rm H_2$ abundance ratio in molecular clouds (and thus their CO line visibility) in starburst galaxies, and find that it can lead to a CO-poor/CI-rich $\rm H_2 $ gas phase even in environments with Galactic or in only modestly enhanced CR backgrounds expected in ordinary star-forming galaxies. Furthermore, the same CR-driven astro-chemistry raises the possibility of a widespread phase transition of molecular gas towards a CO-poor/CI-rich phase in: a) molecular gas outflows found in star-forming galaxies, b) active galactic nuclei (AGNs), and c) near synchrotron-emitting radio jets and the radio-loud cores of powerful radio galaxies. For main sequence galaxies we find that CRs can render some of their molecular gas mass CO-invisible, compounding the effects of low metallicities. Imaging the two fine structure lines of atomic carbon with resolution high enough to search beyond the CI/CO-bright line regions associated with central starbursts can reveal such a CO-poor/CI-rich molecular gas phase, provided that relative brightness sensitivity levels of $T_b$(CI $1-0$)/$T_b$(CO $J=1-0$)$\sim $0.15 are reached. The capability to search for such gas in the Galaxy is now at hand with the new high-frequency survey telescope HEAT deployed in Antarctica and future ones to be deployed in Dome A. ALMA can search for such gas in star-forming spiral disks, galactic molecular gas outflows and the CR-intense galactic and circumgalactic gas-rich environments of radio-loud objects.