1. Borislav Nedelchev et al. 2019
The insignificance of Seyfert 2 activity in driving cold-gas galactic winds
Borislav Nedelchev et al. 2019
Hi, everyone, today I’d like to give a review on a paper focused on AGN feedback. The title is …, and the author is here. Please forgive me that I don’t know how to pronunciate it.

2. The connection between SMBHs and Galaxies
So it’s a story between SMBHs and the entire galaxies. We know that almost every galaxy harbors a SMBH at its center. And the mass of the BH ranges from 10^5-10^10 solar mass. These tell us there is a connection between the growth of BHs and the evolution of galaxies. So what’s the exactly connection? AGN feedback. AGN feedback is often invoked as a mechanism for suppressing star formation since stellar winds or SN explosion cannot efficiently expel gas from their gravitational potential wells.

3. AGNs can be divided into two subclasses
AGNs can be divided into two subclasses. One is radiative-mode, including qsos and Seyfert galaxies. Their host galaxies can be early-type and late-type galaxies. They have strong radiation and thus significant outflow or wind. The energy released by the AGN will heat or eject the surrounding gas and thus quench the SF.

5. a: M87 galaxy with its AGN shocking gas around it; b: Radio lobes of AGN (red), seen alongside X-ray intra-cluster gas (blue), a clear signature of quantitative AGN feedback
 the radio jets seen in kinetic mode expel radio-heated gas from the accreting black hole matter outwards into the intra-cluster medium (ICM) and push away the existing X-ray heated cluster gas away.  It’s AGN feedback in positive manner since the jet gas will compress the one in the ICM and then cool by radiation.

7. Fraunhofer lines in the solar spectrum
They use neutral Na absorption line (Na D) to trace the cool gas.

8. Sample （from SDSS）
Seyfert 2 (classified by BPT diagram, z < 0.2, 9859 objects)
A/N (amplitude-to-noise of prominent emission lines) > 3
Control sample (five control galaxies for each Seyfert 2 galaxy)
Redshift
Absolute r-band magnitude
Apparent flattening (b/a)
The radius containing 90% of the Petrosian flux
The radius containing 50% of the Petrosian flux
U-R color
They combine these quantities with a weight and to find the best results by minimizing the sum of the absolute differences in relative terms.

11. SDSS color images for Seyfert and control galaxies
SDSS color images for Seyfert and control galaxies. The 1st column is the Seyfert 2 galaxies and the next five columns are the five closest-matched control galaxies.

12. Data analysis Normalize the SDSS spectra (Na D region)
Fit the Na D absorption profile

13. The incidence of Na D interstellar absorption
We can see that the fraction with NaD of these two subsamples, seyfert2 and control, are close, 5.7% versus 4.9%.and as to the outflows. The incidence of control sample is higher. This tell us it not AGN, but SF, play the dominant role in driving cold-gas outflows. optical AGN are not direct significant contributors to the quenching of star formation in the nearby Universe, and that star-formation may actually be the principal driver of outflows even in systems that do host an unobscured AGN.

14. Results Galaxies with ∆𝑉<−100 𝑘𝑚 𝑠 −1 is likely to host
cool gas outflow, which are expected to be on
kpc scales.
Compared to the control sample, however, the tail
of objects with blue-shifted Na D profiles is less
pronounced
Two quantities are used to probed the NaD absorption lines. Delta sigma and delta V, V and velocity dispersion is is compared to the galaxy’s systemic velocity and central velocity dispersion.

15. Is AGN activity important in driving galactic winds?
AGNs with higher luminosity should have a stronger
wind, but not found in this result (the trend is weak).

16. Is SF activity important in driving galactic winds?

17. Conclusions
The incidence of detected Na D absorption across our Seyfert 2 and control samples are similar (5.7% VS 4.9%)
Out of 9859 Seyfert 2 galaxies, only 53 show evidence of kpc-scale cold- gas outflows
The overall cold-gas kinematic behaviour traced by the Na D interstellar absorption in Seyfert 2 and control galaxies is rather similar
Consistent with previous studies, many Na D-outflowing Seyfert 2 galaxies are some of the brightest AGN
Radio and IR data of our Seyferts suggests that star-formation is likely to be the bigger contributor to the observed Na D-outflows