Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

A Potential Link between Nuclear Winds and Cold Gas Outflows on Kiloparsec Scales in Reionization-Era Quasars

Yongda Zhu, Marcia J. Rieke, Luis C. Ho, Yang Sun, George H. Rieke, Feng Yuan, Tom J. L. C. Bakx, George D. Becker, Jinyi Yang, Eduardo Bañados, Manuela Bischetti, Christopher Cain, Xiaohui Fan, Yoshinobu Fudamoto, Seyedazim Hashemi, Ryota Ikeda, Zhiyuan Ji, Xiangyu Jin, Weizhe Liu, Yichen Liu, Jianwei Lyu, Hai-Xia Ma, Tsutomu T. Takeuchi, Hideki Umehata, Feige Wang, Wei Leong Tee

Abstract

Feedback from accreting supermassive black holes may regulate galaxy evolution, but statistical evidence linking nuclear winds to kiloparsec-scale cold gas outflows remains limited in the early universe. Here we report statistical evidence for such a connection in a sample of luminous quasars at $z \sim 5.5$. We compare stacked [C II] 158 $μ$m emission profiles from ALMA observations, which trace galactic-scale neutral gas, for quasars with and without broad absorption lines (BALs) that indicate powerful nuclear winds on sub-kiloparsec scales. A total of 5 BAL and 11 non-BAL quasar spectra are included in the stacking analysis. The BAL quasar stack exhibits a potential blueshifted broad component in the [C II] line profile, with a velocity offset of $Δv_{\rm b} = -2.1 \times 10^2\,\rm km\,s^{-1}$ and a full width at half maximum of $1.18 \times 10^3\,\rm km\,s^{-1}$, whereas the non-BAL stack shows no obvious broad component. Using a conservative ``clean-stack'' selection that excludes quasars with partial [C II] spectral coverage, the BAL broad residual is reduced to a hint-level feature. We estimate that up to a few percent to one-quarter of the nuclear wind energy may be transferred to cold neutral gas on kiloparsec scales. Although the sample size is limited, these results suggest a potential link between BAL winds and cold gas feedback in quasar host galaxies. These results provide empirical motivation for future tests of how multiphase outflows relate to the diversity of quasar host properties, including $M_{\rm BH}/M_*$.

A Potential Link between Nuclear Winds and Cold Gas Outflows on Kiloparsec Scales in Reionization-Era Quasars

Abstract

Feedback from accreting supermassive black holes may regulate galaxy evolution, but statistical evidence linking nuclear winds to kiloparsec-scale cold gas outflows remains limited in the early universe. Here we report statistical evidence for such a connection in a sample of luminous quasars at . We compare stacked [C II] 158 m emission profiles from ALMA observations, which trace galactic-scale neutral gas, for quasars with and without broad absorption lines (BALs) that indicate powerful nuclear winds on sub-kiloparsec scales. A total of 5 BAL and 11 non-BAL quasar spectra are included in the stacking analysis. The BAL quasar stack exhibits a potential blueshifted broad component in the [C II] line profile, with a velocity offset of and a full width at half maximum of , whereas the non-BAL stack shows no obvious broad component. Using a conservative ``clean-stack'' selection that excludes quasars with partial [C II] spectral coverage, the BAL broad residual is reduced to a hint-level feature. We estimate that up to a few percent to one-quarter of the nuclear wind energy may be transferred to cold neutral gas on kiloparsec scales. Although the sample size is limited, these results suggest a potential link between BAL winds and cold gas feedback in quasar host galaxies. These results provide empirical motivation for future tests of how multiphase outflows relate to the diversity of quasar host properties, including .

Paper Structure

This paper contains 13 sections, 8 equations, 9 figures.

Table of Contents

  1. Introduction
  2. Data
  3. ALMA Observations
  4. ESI Spectra
  5. Stacked [C II] Spectra
  6. Discussion
  7. Nuclear Winds and the Origin of the [C ii] Wing
  8. Energetics and Coupling Efficiency Between BAL and Cold Gas Outflows
  9. Intrinsic Properties of Quasars and Sample Size
  10. Robustness of Stacking Methods and Interpretation
  11. Individual Quasar: J0056+2241
  12. Summary
  13. The Quasar Sample

Figures (9)

  • Figure 1: Stacked [C ii] spectra. (a) Stacked [C ii] profile for the BAL quasar sample. The top panel shows the number of spectra contributing to the stack at each velocity bin ($\Delta v$). The middle panel displays the normalized [C ii] flux, with the best-fit narrow (green) and broad (magenta) Gaussian components. The combined model is shown in black, with a broad component centered at $\Delta v_{\rm b} = -2.1\times10^2 \, \rm km\,s^{-1}$ and a FWHM of $1.18\times10^3 \, \rm km\,s^{-1}$. The residuals between the total flux and the narrow component are shown in the third panel, highlighting the significance of the broad residual (mean S/N = 4.45 within the FWHM). The bottom panel shows the overall residuals after subtracting the total model. (b) Stacked [C ii] profile for the non-BAL quasar sample. The profile shows no obvious broad residual, with residuals below 2$\sigma$. Panels (c) and (d) provide a conservative "clean-stack" check excluding quasars with partial [C ii] spectral coverage.
  • Figure 2: UV magnitude ($M_{1450}$) versus redshift for the quasars used in this work. The five quasars with strong BAL features (${\rm BI}_0 > 1000$ km s$^{-1}$) are used to create the stacked [C ii] profile shown in Figure \ref{['fig:stacked']}(a).
  • Figure 3: Cumulative distribution of the S/N of the broad component based on random stacks of five non-BAL quasars. The probability of reproducing an S/N=4.4 detection of the broad [C ii] component in non-BAL quasars is less than 0.02. This null test disfavors pure-noise explanations for the full-stack BAL broad residual, although the conservative clean-stack analysis yields only a hint-level feature. Systematic effects related to data reduction or continuum subtraction are not an obvious explanation for the full-stack residual.
  • Figure 4: [C ii] emission from the stacked image cubes of BAL (left panel) and non-BAL (right panel) quasars. The black curves represent the normalized flux (arbitrary units), while the blue shaded regions show the residual flux after subtracting the narrow component. The gray shaded regions indicate the $\pm 1\sigma$ noise level. The fitting parameter uncertainties shown in this plot are derived from a single stack, rather than the bootstrap approach used in Figure \ref{['fig:stacked']}. When stacking image cubes instead of 1D spectra, the BAL sample still exhibits a significant broad component at $4.48\sigma$, whereas the non-BAL sample remains below the $2\sigma$ detection threshold.
  • Figure 5: Jackknife tests of the [C ii] stacked spectrum for the BAL QSO sample. Each panel shows the stack of 4 out of 5 BAL quasars, with one excluded. The broad component remains visible across all tests, but its S/N decreases when excluding J0012, indicating that the result is not solely driven by a single source.
  • ...and 4 more figures