Stellar feedback as the origin of an extended molecular outflow in a starburst galaxy

Geach, J. E.; Hickox, Ryan C.; Diamond‐Stanic, Aleksandar M.; Krips, M.; Rudnick, Gregory; Tremonti, Christy; Sell, Paul H.; Coil, A. L.; Moustakas, John

doi:10.1038/nature14012

Cited by 73 publications

(94 citation statements)

References 40 publications

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“…Again, this is a good description of our numerical results tabulated in Table 1, with η shock = 0.4 and η rocket = 0.6, giving the best match. We should add one caveat about our assumption to prevent cooling below temperatures of 10 4 K when several observations of outflows do show a molecular component (e.g., Geach et al 2014). With an HI photo-ionization cross-section of 6.3 × 10 −18 cm 2 , the cloud simulated in this paper would become Figure 7.…”

Section: Discussion and Summarymentioning

confidence: 99%

The Launching of Cold Clouds by Galaxy Outflows. Ii. The Role of Thermal Conduction

Brüggen

Scannapieco

2016

ApJ

130

123

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We explore the impact of electron thermal conduction on the evolution of radiatively cooled cold clouds embedded in flows of hot and fast material as it occurs in outflowing galaxies. Performing a parameter study of threedimensional adaptive mesh refinement hydrodynamical simulations, we show that electron thermal conduction causes cold clouds to evaporate, but it can also extend their lifetimes by compressing them into dense filaments. We distinguish between low column-density clouds, which are disrupted on very short times, and high-column density clouds with much longer disruption times that are set by a balance between impinging thermal energy and evaporation. We provide fits to the cloud lifetimes and velocities that can be used in galaxy-scale simulations of outflows in which the evolution of individual clouds cannot be modeled with the required resolution. Moreover, we show that the clouds are only accelerated to a small fraction of the ambient velocity because compression by evaporation causes the clouds to present a small cross-section to the ambient flow. This means that either magnetic fields must suppress thermal conduction, or that the cold clouds observed in galaxy outflows are not formed of cold material carried out from the galaxy.

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Section: Discussion and Summarymentioning

confidence: 99%

The Launching of Cold Clouds by Galaxy Outflows. Ii. The Role of Thermal Conduction

Brüggen

Scannapieco

2016

ApJ

130

123

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“…Although our simplified model provides a very good result, a homogeneous distribution of gas and dust seems clearly inconsistent with observations of real ISMs. There is indeed ample evidence for a multiphase ISM in star-forming galaxies, galactic fountains, and outflowing halos (Geach et al 2014;Veilleux et al 2009;Cox & Smith 1974;McKee & Ostriker 1977;McKee 1995;Spitzer 1990;Mac Low & Klessen 2004). In the most frequently employed picture of McKee & Ostriker (1977), most of the volume of the ISM is occupied by hot (HIM, T ≈ 10 6 K), warm (WNM, T ≈ 10 4 K), and cold (molecular phase, T ≈ 10 2 K) media in thermal equilibrium.…”

Section: Hi and Dust Clumpiness Inside The Disk And The Outflowing Halosmentioning

confidence: 99%

The Lyman alpha reference sample

Duval

Östlin

Hayes

et al. 2016

A&A

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Context. Recent numerical simulations suggest that the strength of the Lyman alpha (Lyα) line of star-forming disk galaxies strongly depends on the inclination at which they are observed: from edge-on to face-on, we expect to see a change from a strongly attenuated Lyα line to a strong Lyα emission line. Aims. We aim to understand how a strong Lyα emission line is able to escape from the low-redshift highly inclined (edge-on) disk galaxy Mrk 1486 (z ∼ 0.0338). To our knowledge, this work is the first observational study of Lyα transport inside an edge-on disk galaxy. Methods. Using a large set of HST imaging and spectroscopic data, we investigated the interstellar medium (ISM) structure and the dominant source of Lyα radiation inside Mrk 1486. Moreover, using a 3D Monte Carlo Lyα radiation transfer code, we studied the radiative transfer of Lyα and UV continuum photons inside a 3D geometry of neutral hydrogen (HI) and dust that models the ISM structure at the galaxy center. Our numerical simulations predicted the Lyα line profile that we then compared to the one observed in the HST/COS spectrum of Mrk 1486. Results. While a pronounced Lyα absorption line emerges from the disk of Mrk 1486, very extended Lyα structures are observed at large radii from the galaxy center: a large Lyα-halo and two very bright Lyα regions located slightly above and below the disk plane. The analysis of IFU Hα spectroscopic data of Mrk 1486 indicates the presence of two bipolar outflowing halos of HI gas at the same location as these two bright Lyα regions. Comparing different diagnostic diagrams (such as [OIII] 5007 /Hβ versus [OI] 6300 /Hα) to photo-and shock-ionization models, we find that the Lyα production of Mrk 1486 is dominated by photoionization inside the galaxy disk. From this perspective, our numerical simulations succeed in reproducing the strength and shape of the observed Lyα emission line of Mrk 1486 by assuming a scenario in which the Lyα photons are produced inside the galaxy disk, travel along the outflowing halos, and scatter on cool HI materials toward the observer. Conclusions. Extended bipolar galactic winds are frequently observed from star-forming disk galaxies. Given the advantage Lyα photons take of such outflowing HI materials to easily escape from Mrk 1486, this mechanism may explain the origin of strong Lyα emission lines frequently observed from highly inclined galaxies at high-redshift. This therefore challenges the robustness of the expected viewing-angle effect on the Lyα properties of star-forming disk galaxies.

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“…This factor is assumed to be between 0.4 × 10 20 cm −2 (K km s −1 ) −1 (α CO = 0.8), typical of a thick and dense medium and commonly used for ULIRG, and 0.2 × 10 20 cm −2 (K km s −1 ) −1 (corresponding to α CO = 0.34, the most conservative case) derived for optically thin cases and suggested for turbulent gas associated with winds (see the discussion in Bolatto et al 2013 andin Geach et al 2014). Using these two values for the CO-to-H 2 conversion factor, we derive masses for the anomalous molecular gas, ranging between 1.9 and 4.8 × 10 7 M , of which between 0.5 and 1.3 × 10 7 M is associated with the gas with the most extreme kinematics at the location of the W lobe.…”

Section: Molecular Gas Massesmentioning

confidence: 99%

The fast molecular outflow in the Seyfert galaxy IC 5063 as seen by ALMA

Morganti

Oosterloo

Oonk

et al. 2015

A&A

217

269

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We use high-resolution (0.5 arcsec) CO(2−1) observations performed with the Atacama Large Millimetre/submillimetre Array to trace the kinematics of the molecular gas in the Seyfert 2 galaxy IC 5063. The data reveal that the kinematics of the gas is very complex. A fast outflow of molecular gas extends along the entire radio jet (∼1 kpc), with the highest outflow velocities about 0.5 kpc from the nucleus, at the location of the brighter hot spot in the western lobe. The ALMA data show that a massive, fast outflow with velocities up to 650 km s −1 of cold molecular gas is present, in addition to the outflow detected earlier in warm H 2 , H i and ionized gas. All phases of the gas outflow show similar kinematics. IC 5063 appears to be one of the best examples of the multi-phase nature of AGN-driven outflows. Both the central AGN and the radio jet could energetically drive the outflow, however, the characteristics of the outflowing gas point to the radio jet being the main driver. This is an important result because IC 5063, although one of the most powerful Seyfert galaxies, is a relatively weak radio source (P 1.4 GHz = 3 × 10 23 W Hz −1 ). All the observed characteristics can be described by a scenario of a radio plasma jet expanding into a clumpy medium, interacting directly with the clouds and inflating a cocoon that drives a lateral outflow into the interstellar medium. This model is consistent with results obtained by recent simulations. A stronger, direct interaction between the jet and a gas cloud is present at the location of the brighter western lobe. This interaction may also be responsible for the asymmetry in the radio brightness of the two lobes. Even assuming the most conservative values for the conversion factor CO-to-H 2 , we find that the mass of the outflowing gas is between 1.9 and 4.8 × 10 7 M , of which between 0.5 and 1.3 × 10 7 M is associated with the fast outflow at the location of the western lobe. These amounts are much larger than those of the outflow of warm gas (molecular and ionized) and somewhat larger than of the H i outflow. This suggests that most of the observed cold molecular outflow is due to fast cooling after being shocked. This gas is the end product of the cooling process, although some of it could be the result of only partly dissociated clouds. Our CO observations demonstrate that fast outflows of substantial masses of molecular gas can be driven by relativistic jets, although in the case of IC 5063 the outflows are not fast enough to remove significant amounts of gas from the galaxy and the effects are limited to the central ∼0.5 kpc from the centre.

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Stellar feedback as the origin of an extended molecular outflow in a starburst galaxy

Cited by 73 publications

References 40 publications

The Launching of Cold Clouds by Galaxy Outflows. Ii. The Role of Thermal Conduction

The Launching of Cold Clouds by Galaxy Outflows. Ii. The Role of Thermal Conduction

The Lyman alpha reference sample

The fast molecular outflow in the Seyfert galaxy IC 5063 as seen by ALMA

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