Galaxy pairs in the Sloan Digital Sky Survey – XV. Properties of ionized outflows
ABSTRACT

Powerful outflows are thought to play a critical role in galaxy evolution and black hole growth. We present the first large-scale systematic study of ionized outflows in paired galaxies and post-mergers compared to a robust control sample of isolated galaxies. We isolate the impact of the merger environment to determine if outflow properties depend on merger stage. Our sample contains ∼4000 paired galaxies and ∼250 post-mergers in the local universe (0.02 ≤ z ≤ 0.2) from the Sloan Digital Sky Survey Data Release 7 (SDSS DR 7) matched in stellar mass, redshift, local density of galaxies, and [O iii] λ5007 luminosity to a control sample of isolated galaxies. By fitting the [O iii] λ5007 line, we find ionized outflows in ∼15 per cent of our entire sample. Outflows are much rarer in star-forming galaxies compared to active galactic nuclei (AGNs), and outflow incidence and velocity increase with [O iii] λ5007 luminosity. Outflow incidence is significantly elevated in the optical + mid-infrared selected AGN compared to purely optical AGN; over 60 per cent show outflows at the highest luminosities ($L_{\mathrm{[OIII]~\lambda 5007}}\, \gtrsim$ 1042 erg s−1), suggesting mid-infrared AGN selection favours galaxies with powerful outflows, at least for higher [O iii] λ5007 luminosities. However, we find no statistically significant difference in outflow incidence, velocity, and luminosity in more »

Authors:
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Award ID(s):
Publication Date:
NSF-PAR ID:
10368759
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
514
Issue:
4
Page Range or eLocation-ID:
p. 4828-4844
ISSN:
0035-8711
Publisher:
Oxford University Press
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Using ALMA and PdBI observations, we spatially resolve the CO(1-0) emission from the outflowing molecular gas in both and find maximum outflow velocities of$ v_{\rm max} \sim 1600$and$\sim 1700$km/s for IRAS 20100-4156 and IRAS 03158+4227, respectively. We find total gas mass outflow rates of$\dot M_{\rm OF} \sim 670$and$\sim 350$Msun/yr, respectively, corresponding to molecular gas depletion timescales$\tau^{\rm dep}_{\rm OF} \sim 11$and$\sim 16$Myr. This is nearly 3 times shorter than the depletion timescales implied by star formation,$\tau^{\rm dep}_{\rm SFR} \sim 33$and$\sim 46$Myr, respectively. To determine the outflow driving mechanism, we compare the starburst ($L_{*}$) and AGN ($L_{\rm AGN}$) luminosities to the outflowing energy and momentum fluxes, using mid-infrared spectral decomposition to discern$L_{\rm AGN}$. Comparison to other molecular outflows in ULIRGs reveals that outflow properties correlate similarly with$L_{*}$and$L_{\rm IR}$as with$L_{\rm AGN}\$, indicating that AGN luminosity alone may not be a good tracer of feedback strength and that a combination of AGN and starburstmore »