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MAUVE: Cold neutral gas in the outflow of NGC 4383 and evidence for a fountain flow

L. Cortese, A. B. Watts, J. Sun, S. Sankar, B. Catinella, T. Brown, A. Boselli, P. Jáchym, T. Kolcu, S. Thater, J. van de Sande, V. Villanueva

TL;DR

This study investigates the multiphase outflow in NGC 4383 by combining ALMA CO(2-1), MeerKAT HI, and VLT/MUSE data to trace molecular, atomic, and ionised gas. The molecular component is confined to the inner ~1 kpc with disturbed kinematics, while the atomic hydrogen forms extraplanar plumes aligned with the ionised outflow and, together with dust, indicates a cold gas phase entrained in the wind. The analysis suggests that the atomic phase dominates the cold outflow mass beyond ~1 kpc and that the observed outflow velocities for the cold gas remain below the ionised gas, supporting a galactic fountain scenario rather than a large-scale escaping wind. These findings emphasize that in gas-rich galaxies the cold gas primarily cycles between the disc and halo, highlighting the need for high-resolution, multiphase observations to understand the baryon cycle and feedback effects in galaxy evolution.

Abstract

We present a multiphase study of the star-formation-driven outflow in the Virgo galaxy NGC 4383, combining ALMA CO(2-1) data with deep MeerKAT HI imaging and MUSE spectroscopy obtained as part of the Multiphase Astrophysics to Unveil the Virgo Environment (MAUVE) program. Our previous work revealed a spectacular ionised outflow, but the effect of the outflow on the cold phase remained unclear. Our analysis shows that potentially outflowing molecular gas is detected only within the inner 1 kpc above the disc, where CO clouds exhibit disturbed kinematics and spatial correspondence with the ionisation cone. At larger heights, the CO surface brightness rapidly drops, indicating that the molecular phase contributes little to the mass of outflowing gas. In contrast, the HI distribution shows plumes a few kiloparsecs above the disc that are aligned with the ionised cone, and complex kinematics suggestive of parts of the atomic phase being entrained in the outflow. However, the extended and warped HI disc associated with NGC 4383 complicates the unambiguous identification of outflowing atomic gas and, most importantly, the quantification of outflowing mass and loading factor. Independent support for a cold component in the outflow comes from dust extinction features associated with the outflow and coincident with HI plumes. Despite significant uncertainties in the estimate of the mass of cold gas associated with the outflow, these results suggest that the atomic phase likely dominates the cold outflow above 1 kpc. The observed cold gas velocities remain below the velocities of the ionised phase, suggesting that NGC 4383 does not host a large-scale escaping wind but more likely a galactic fountain, in which feedback redistributes material within the halo and regulates ongoing and future star formation.

MAUVE: Cold neutral gas in the outflow of NGC 4383 and evidence for a fountain flow

TL;DR

This study investigates the multiphase outflow in NGC 4383 by combining ALMA CO(2-1), MeerKAT HI, and VLT/MUSE data to trace molecular, atomic, and ionised gas. The molecular component is confined to the inner ~1 kpc with disturbed kinematics, while the atomic hydrogen forms extraplanar plumes aligned with the ionised outflow and, together with dust, indicates a cold gas phase entrained in the wind. The analysis suggests that the atomic phase dominates the cold outflow mass beyond ~1 kpc and that the observed outflow velocities for the cold gas remain below the ionised gas, supporting a galactic fountain scenario rather than a large-scale escaping wind. These findings emphasize that in gas-rich galaxies the cold gas primarily cycles between the disc and halo, highlighting the need for high-resolution, multiphase observations to understand the baryon cycle and feedback effects in galaxy evolution.

Abstract

We present a multiphase study of the star-formation-driven outflow in the Virgo galaxy NGC 4383, combining ALMA CO(2-1) data with deep MeerKAT HI imaging and MUSE spectroscopy obtained as part of the Multiphase Astrophysics to Unveil the Virgo Environment (MAUVE) program. Our previous work revealed a spectacular ionised outflow, but the effect of the outflow on the cold phase remained unclear. Our analysis shows that potentially outflowing molecular gas is detected only within the inner 1 kpc above the disc, where CO clouds exhibit disturbed kinematics and spatial correspondence with the ionisation cone. At larger heights, the CO surface brightness rapidly drops, indicating that the molecular phase contributes little to the mass of outflowing gas. In contrast, the HI distribution shows plumes a few kiloparsecs above the disc that are aligned with the ionised cone, and complex kinematics suggestive of parts of the atomic phase being entrained in the outflow. However, the extended and warped HI disc associated with NGC 4383 complicates the unambiguous identification of outflowing atomic gas and, most importantly, the quantification of outflowing mass and loading factor. Independent support for a cold component in the outflow comes from dust extinction features associated with the outflow and coincident with HI plumes. Despite significant uncertainties in the estimate of the mass of cold gas associated with the outflow, these results suggest that the atomic phase likely dominates the cold outflow above 1 kpc. The observed cold gas velocities remain below the velocities of the ionised phase, suggesting that NGC 4383 does not host a large-scale escaping wind but more likely a galactic fountain, in which feedback redistributes material within the halo and regulates ongoing and future star formation.
Paper Structure (15 sections, 11 figures)

This paper contains 15 sections, 11 figures.

Table of Contents

  1. Introduction
  2. Data
  3. ALMA CO (2--1) data
  4. MeerKAT H i data
  5. MUSE and optical imaging data
  6. Results
  7. The impact of the starburst on the molecular gas disc
  8. Searching for the atomic phase of the outflow
  9. Discussion
  10. Summary
  11. Acknowledgments
  12. Funding Statement
  13. Data Availability Statement
  14. Author Contributions
  15. CO(2-1) position-velocity diagram at 500 parsec resolution.

Figures (11)

  • Figure 1: The CO(2-1) morphology of NGC 4383. CO(2-1) intensity contours overlaid on a broad band $g$, $i$ and $z$ colour composite from NGVS (left) and H$\alpha$+[NII] net image from VESTIGE (right). Contours are shown at 0.9, 2.8, 9.2, 27.6 K km s$^{-1}$ levels corresponding to $\sim$5, 15, 50, 150 M$_{\odot}$ pc$^{-2}$ assuming a Milky Way conversion factor (see Sec. 2.1). The footprint of the ALMA observations is shown in light grey, with the size of synthesised beam shown in the bottom left of each panel.
  • Figure 2: The line-of-sight velocity fields of NGC 4383. Comparison between the CO(2-1) (left), the MUSE H$\alpha$ (middle) and the MUSE stellar (right) line-of-sight velocity fields. The black countours in both maps indicate H$\alpha$ velocities of 1695, 1755 (thick) and 1715 and 1735 (thin) km s$^{-1}$, respectively. The size of the ALMA synthesized beam is shown in the bottom left of the left panel. Fore reference, the ‘x’ marks the assumed kinematic centre of the CO emission.
  • Figure 3: Position-velocity diagrams for the CO(2-1) emission.Left: CO(2-1) line-of-sight velocity field. The slits used to extract the PV diagrams are overlaid. Interesting kinematic features are indicated from A to E. The size of the ALMA synthesized beam is shown in the bottom left. Middle and Right: PV diagrams. The position of each slit is indicated in the bottom-left corner of each sub-plot, with regions identified in the line-of-sight velocity field highlighted with the corresponding letter.
  • Figure 4: [SII]/H$\alpha$ line ratio and CO(2-1) kinematics.Top: CO(2-1) line of sight velocity field. Bottom: [SII]/H$\alpha$ line ratio map. In both panels the black contour indicates $\log$([SII]/H$\alpha$)=$-$0.35
  • Figure 5: The H i disc of NGC 4383 as revealed by MeerKAT. H i surface density contours (top-left) superposed on the H i moment 1 (top-right), VESTIGE H$\alpha+[NII]$ narrow-band image (bottom-left) and H i effective width (bottom-right) maps. Contours are shown at 1, 2 (thin), 5, 6, 7, 10, 15, 20 and 30 (thick) M$_{\odot}$ pc$^{-2}$. The background image shows the optical broad-band $u$,$g$,$i$ colour composite from NGVS. The synthesized beam of the H i observations is shown in the bottom-left corner of each panel.
  • ...and 6 more figures