Profile of and Variability in Double-Peaked Balmer Emission Lines in 3C 445

TL;DR

This study analyzes over three decades of spectral data of quasar 3C 445, revealing variability in its double-peaked Balmer emission lines and suggesting shock-heated outflows as the cause.

Contribution

It provides a long-term spectral analysis of 3C 445's emission lines, highlighting the variability and potential shock-related origins of the blue emission component.

Findings

The blue system of Hα disappeared suddenly and did not reappear.

Both Balmer lines share similar profiles, with differences in the blue component.

The blue component is likely caused by shock-heated outflowing gases.

Abstract

We extract the multiple-epoch Balmer-line profiles of the heavily obscured quasar 3C 445 from the spectral curves in the literature, and analyze the emission-line profiles of the H$\alpha$ and H$\beta$ lines and the profile variability in the H$\alpha$ line in the large time interval of more than three decades. The profile comparison between the H$\alpha$ and H$\beta$ lines shows that both Balmer lines share the profile with the same form, while the blue system of the H$\beta$ line is seriously weaker than that of the H$\alpha$ line. Moreover, the blue system of the H$\alpha$ line suddenly disappeared completely and then did not appear again, however the other two components did not exhibit significant variation in the velocity or the amplitude. These findings suggest that the blue system of 3C 445, as with SDSS J153636.22+044127.0 and its analogs, is probable the result of the shock-heated outflowing gases. The observation angle of almost edge-on which the previous studies suggested can easily produce the high-speed and high-temperature shock in the collision between the massive outflow and the inner surface of the dusty torus.