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Positive AGN feedback in the outskirts of nearby barred spiral galaxies?

Bannanje Ananthamoorthy, Debbijoy Bhattacharya, P. Sreekumar

TL;DR

This study investigates whether low-luminosity AGN can positively influence star formation in the outer disks of nearby barred spiral galaxies. Using high-resolution UV imaging from AstroSat-UVIT and archival GALEX data, the authors detect UV star-forming knots beyond $0.5R_{25}$ in six AGN-hosts and four barred non-AGN galaxies, deriving knot-by-knot SFRs and attenuation-corrected UV luminosities. They find that the outer regions of AGN-host galaxies exhibit higher $ ext{Σ}_{ ext{SFR}}$ and greater $A_{ ext{FUV}}$ with a slower radial decline compared with non-AGN controls, and that the slopes of these radial profiles are marginally flatter for AGN hosts. Statistical tests (KS and Anderson-Darling) support, at around the 95–96% level, that AGN hosts have systematically different outer-disk SF profiles, consistent with radiation-pressure-driven and/or wind-driven dust-coupled feedback, even in low-luminosity nearby AGN. The work highlights the potential for positive AGN feedback to enhance star formation in outer disk regions and underscores the need for larger, deeper, multiwavelength surveys to identify the dominant mechanism and quantify its prevalence.

Abstract

Observational evidence regarding the impact of AGN feedback on star formation (SF) in non-jetted galaxies is limited. With the available high-resolution UV observations from AstroSat-UVIT, complemented by GALEX, we studied the SF properties in the outskirts ($>0.5R_{25}$) of six AGN-host galaxies and compared them with four non-AGN galaxies of similar morphology. We observed a higher SF rate density ($Σ_{\text{SFR}}$) for the UV knots in AGN-host galaxies, and it falls off less rapidly compared to non-AGN galaxies, suggesting positive AGN feedback in the outskirts of AGN-host galaxies. Additionally, FUV attenuation (A$_{\text{FUV}}$) is also enhanced in the outer regions and falls less rapidly in AGN-host compared to non-AGN, indicating that the feedback could be coupled with dust. We speculate that the radiation-pressure-driven and/or wind mode AGN feedback could be at play even in low-luminosity nearby AGN-host galaxies.

Positive AGN feedback in the outskirts of nearby barred spiral galaxies?

TL;DR

This study investigates whether low-luminosity AGN can positively influence star formation in the outer disks of nearby barred spiral galaxies. Using high-resolution UV imaging from AstroSat-UVIT and archival GALEX data, the authors detect UV star-forming knots beyond in six AGN-hosts and four barred non-AGN galaxies, deriving knot-by-knot SFRs and attenuation-corrected UV luminosities. They find that the outer regions of AGN-host galaxies exhibit higher and greater with a slower radial decline compared with non-AGN controls, and that the slopes of these radial profiles are marginally flatter for AGN hosts. Statistical tests (KS and Anderson-Darling) support, at around the 95–96% level, that AGN hosts have systematically different outer-disk SF profiles, consistent with radiation-pressure-driven and/or wind-driven dust-coupled feedback, even in low-luminosity nearby AGN. The work highlights the potential for positive AGN feedback to enhance star formation in outer disk regions and underscores the need for larger, deeper, multiwavelength surveys to identify the dominant mechanism and quantify its prevalence.

Abstract

Observational evidence regarding the impact of AGN feedback on star formation (SF) in non-jetted galaxies is limited. With the available high-resolution UV observations from AstroSat-UVIT, complemented by GALEX, we studied the SF properties in the outskirts () of six AGN-host galaxies and compared them with four non-AGN galaxies of similar morphology. We observed a higher SF rate density () for the UV knots in AGN-host galaxies, and it falls off less rapidly compared to non-AGN galaxies, suggesting positive AGN feedback in the outskirts of AGN-host galaxies. Additionally, FUV attenuation (A) is also enhanced in the outer regions and falls less rapidly in AGN-host compared to non-AGN, indicating that the feedback could be coupled with dust. We speculate that the radiation-pressure-driven and/or wind mode AGN feedback could be at play even in low-luminosity nearby AGN-host galaxies.

Paper Structure

This paper contains 18 sections, 2 equations, 4 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Sample and Data
  3. Sample
  4. Data
  5. AstroSat-UVIT
  6. Galaxy evolution explorer (GALEX)
  7. Analysis and Results
  8. Astrometry
  9. UV Analysis and SFR calculation
  10. Effect of mergers
  11. Size of the SF region and $\Sigma_{\text{SFR}}$
  12. $\Sigma_{\text{SFR}}$ and A$_{\text{FUV}}$ in the outer regions of the galaxy:
  13. Kolmogorov–Smirnov and Anderson-Darling test:
  14. Discussion and Conclusions
  15. Effect of bar and mergers
  16. ...and 3 more sections

Figures (4)

  • Figure 1: The flowchart for the criteria used for selection of AGN sample.
  • Figure 2: UVIT images of galaxies in the sample. The first three rows correspond to AGN-host galaxies, and the last two rows correspond to non-AGN galaxies. The ellipse in each image represents the galaxy's optical radius (R$_{25}$). For NGC 1097 (Panel (a)), the position of the companion galaxy, NGC 1097A, is marked in the blue circle. For NGC 1097 and NGC 5194 (Panels (a) and (f)), the shaded elliptical region corresponds to the region affected by the merger. These masked regions are excluded from the study of AGN's impact on these galaxies (see Section-\ref{['sec:Analysis']}).
  • Figure 3: Upper Panel: Ratio of average $\Sigma_{\text{SFR}}$ of AGN-host and non-AGN galaxies as a function of distance from the centre. Lower Panel: Ratio of average A$_{\text{FUV}}$ of AGN-host and non-AGN galaxies as a function of distance from the centre.
  • Figure 4: Panel (a): Slopes of straight lines fitted to the radial profile of $\log_{10}(\Sigma_{\text{SFR}})$ for individual AGN galaxies in the galaxy outskirts as a function of M$_{BH}$. The mean slope for AGN galaxies and the corresponding 1-$\sigma$ error (shaded region) are provided for reference. Panel (b): Same as Panel (a) but for non-AGN galaxies. The mean slope for AGN galaxies is provided for reference. Panel (c): Slopes of straight lines fitted to the radial profile of A$_{\text{FUV}}$ for individual galaxies in the galaxy outskirts as a function of M$_{BH}$. Panel (d): Same as Panel (c) but for non-AGN galaxies.