QSOFEED: Investigating warm molecular, low- and high-ionization atomic gas in six type-2 quasars with GTC/EMIR

Abstract

We present long-slit near-infrared spectroscopic observations of six nearby (z$\sim$0.1) radio-quiet type-2 quasars (QSO2s) from the Quasar Feedback (QSOFEED) sample. They have bolometric luminosities of $10^{45-46}~erg~s^{-1}$ and stellar masses of $ 10^{10.6-11.3}~M_{\odot}$. The observations were obtained with the instrument Espectrógrafo Multiobjeto Infra-Rojo (EMIR) on the 10.4 m Gran Telescopio Canarias. The nuclear K-band spectra (central $\sim$1-3 kpc of the QSO2s) reveal signatures of high-velocity outflows in either the Pa$α$ or Br$γ$ lines, depending on the redshift, and in the [Si VI] lines. The broadest kinematic components have full width at half maximum (FWHM) of $\sim$1200-2500 km $s^{-1}$. From the near-infrared hydrogen recombination lines we derived ionized outflow masses of $M_{Hion} \sim0.08-20\times 10^{6}~M_{\odot}$, mass outflow rates of $\dot{M}_{Hion}\sim0.03-6~M_{\odot}~yr^{-1}$, and kinetic powers of $\dot{E}_{Hion}\sim 10^{37.8-40.8}~erg~s^{-1}$. These ionized gas outflow masses and mass outflow rates have median values that are 5.9 and 5.8 times larger, respectively, than those derived from the [Si VI] line. Our study provides evidence, at least for these six QSO2s, that the near-infrared recombination lines and [Si VI] are tracing the same outflow (i.e., they have similar kinematics and radii), but they carry different amounts of mass. We detected warm molecular lines in the six QSO2s, from which we measured total (nuclear) gas masses from 1.1 (0.7) to 32 (13) $\times~10^3~M_{\odot}$, similar to other QSO2s with warm $H_2$ measurements reported in the literature, but we did not find any molecular outflow associated with them. Comparing with other five QSO2s with $H_2$ measurements reported in the literature, we find that the four QSO2s with detected $H_2$ outflows have total (nuclear) $H_2$ masses 2.2 (2.7) times larger, on average.

Figures (18)

• Figure 1: Sloan Digital Sky Survey (SDSS) gri images of the QSO2s. North is up and east to the left. Horizontal bars in the top left corner of each image indicate the physical size of 5. Images size is 40$\times$40.
• Figure 2: EMIR K-band nuclear spectra of the QSO2s showing the emission lines detected. The spectra were scaled in the Y-axis with the purpose of better visualization and smoothed using a 10 pixels boxcar. The spectra of the QSO2s are displayed from top to bottom in order of increasing redshift. Black dashed vertical lines indicate the position of the atomic lines and dotted lines the $\rm H_2$ lines.
• Figure 3: Examples of emission line fits. The rest-frame spectrum of J1440+53 and residuals are shown in black and the fitted model in red. Narrow (n), intermediate (i), and broad (b) components are shown in green, blue, and magenta. The spectra were smoothed using a 4 pixels boxcar and residuals were scaled up from zero to reduce blank space. Vertical dotted lines correspond to the peak of the narrow component fitted to each line.
• Figure 4: $\rm \dot{M}_{Hion}$ versus $\rm L_{bol}$. Turquoise points are our ionized mass outflow rates ($\rm \dot{M}_{Hion}$), calculated from either Pa$\alpha$ or Br$\gamma$ and using TR-based electron densities. Data of other QSO2s are shown with different colors and symbols. Open squares are mass outflow rates from Fiore+17, divided by 130 (see text). The grey dashed and dotted lines are the scaling relations from Fiore+17 and Davies+20, respectively, and the black solid line is the linear fit to all the data points included in the plot. The orange shaded area represents the 1$\sigma$ confidence interval of the fit.
• Figure 5: Total ionized (Hion) versus [Si VI] gas outflow mass (left panel) and mass outflow rate (right panel). Turquoise circles are the QSO2s studied here, with outflow masses and mass rates calculated with TR electron densities, and blue and yellow circles are the QSO2s J1430+13 and J1509+04 from RamosAlmeida+17RamosAlmeida+19. Black solid lines are the corresponding fits to the data and the orange shaded area represents the 1$\sigma$ confidence interval of the fit. The Pearson correlation coefficient and the associated p-value are indicated in each panel.