Dusty Superwind from a Galaxy with a Compact Obscured Nucleus: Optical Spectroscopic Study of NGC 4418

Ohyama, Youichi; Sakamoto, Kazushi; Aalto, S.; Gallagher, John S.

doi:10.3847/1538-4357/aaf9a5

Cited by 22 publications

(25 citation statements)

References 117 publications

(303 reference statements)

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“…the direction towards VV 655 has emission-line ratios consistent with ionized gas elsewhere in the galaxy. Ohyama et al (2019) also find N 2 1 in the extended ionized medium of the galactic outflow, and their independent analysis of the red emission lines in NGC 4418 agrees with our conclusion that the chemical abundance of the ionized gas is near solar values.…”

Section: Chemical Abundancessupporting

confidence: 88%

“…Since the stellar rotation of the southwest side of NGC 4418 is redshifted (see Fig. 6 of Ohyama et al 2019) and extinction by a dusty polar outflow along the northwest semiminor axis suggests that the northwest side of the galactic disk is the far side (Sakamoto et al 2013;Ohyama et al 2019), the arm-like feature appears to be a trailing structure, as expected.…”

Section: Imaging and Photometrysupporting

confidence: 66%

“…( f ) r-band Petrosian radius from SDSS-III DR 12. (g) From Varenius et al (2017) and this paper (VV 655) and Ohyama et al (2019;NGC 4418). (h) From Varenius et al (2017), as derived from the 1.4 GHz continuum, and this paper.…”

Section: Introductionmentioning

confidence: 93%

“…4). These features suggest that an influx of interstellar matter reached the central zones of NGC 4418 within the past ∼Gyr, leading to enhanced star formation for at least the last 300 Myr (Shi & Gu 2005;Ohyama et al 2019) and possibly fueling AGN activity. The general properties of NGC 4418, including a centrally concentrated power source, substantial molecular medium, and clear presence of dust, are found in a significant fraction (∼1/10−1/4) of early-type field galaxies (e.g., Koda et al 2005;Kaviraj et al 2012;Nyland et al 2017).…”

Section: Introductionmentioning

confidence: 97%

“…González-Alfonso et al 2012;Costagliola et al 2015), including an extremely Compton-thick nuclear region (N(H) 10 25 cm −2 ; Sakamoto et al 2013). Kpc-scale bipolar dust filaments extend from the central regions of NGC 4418 (Evans et al 2003;Sakamoto et al 2013;Ohyama et al 2019), which contain a post-starburst stellar population as well as a possible highly obscured AGN (Roche et al 1986;Evans et al 2003;Shi & Gu 2005;Sakamoto et al 2013;Ohyama et al 2019, see also Sect. 4).…”

Section: Introductionmentioning

confidence: 99%

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VV 655 and NGC 4418: Implications of an interaction for the evolution of a LIRG

Boettcher

Gallagher

Ohyama

et al. 2020

A&A

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Context. VV 655, a dwarf irregular galaxy with HI tidal debris, is a companion to the lenticular luminous infrared galaxy (LIRG) NGC 4418. NGC 4418 stands out among nearby LIRGs due to its dense central concentration of molecular gas and the dusty, bi-polar structures along its minor axis suggestive of a wind driven by a central starburst and possible nuclear activity. Aims. We seek to understand the consequences of the ongoing minor interaction between VV 655 and NGC 4418 for the evolution of the LIRG. Specifically, we consider the origin of the gas supply responsible for the unusual nuclear properties of NGC 4418. Methods. We investigate the structural, kinematic, and chemical properties of VV 655 and NGC 4418 by analyzing archival imaging data and optical spectroscopic observations from the SDSS-III and new spectra from SALT-RSS. We characterize their gas-phase metal abundances and spatially resolved, ionized gas kinematics to better understand whether gas transfer between VV 655 and NGC 4418 resulted in the highly obscured nucleus of the LIRG. Results. The gas-phase metallicity in NGC 4418 significantly exceeds that in VV 655. No kinematic disturbances in the ionized gas are observed along the minor axis of NGC 4418, but we see evidence for ionized gas outflows from VV 655 that may increase the cross-section for gas stripping in grazing collisions. A faint, asymmetric outer arm is detected in NGC 4418 of the type normally associated with galaxy-galaxy interactions. Conclusions. The simplest model suggests that the minor interaction between VV 655 and NGC 4418 produced the unusual nuclear properties of the LIRG via tidal torquing of the interstellar medium of NGC 4418 rather than through a significant gas transfer event. In addition to inducing a central concentration of gas in NGC 4418, this interaction also produced an enhanced star formation rate and an outer tidal arm in the LIRG. The VV 655-NGC 4418 system offers an example of the potential for minor collisions to alter the evolutionary pathways of giant galaxies.

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Section: Chemical Abundancessupporting

confidence: 88%

Section: Imaging and Photometrysupporting

confidence: 66%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

VV 655 and NGC 4418: Implications of an interaction for the evolution of a LIRG

Boettcher

Gallagher

Ohyama

et al. 2020

A&A

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Cool outflows in galaxies and their implications

Veilleux

Maiolino

Bolatto

et al. 2020

Astron Astrophys Rev

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420

310

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Neutral-atomic and molecular outflows are a common occurrence in galaxies, near and far. They operate over the full extent of their galaxy hosts, from the innermost regions of galactic nuclei to the outermost reaches of galaxy halos. They carry a substantial amount of material that would otherwise have been used to form new stars. These cool outflows may have a profound impact on the evolution of their host galaxies and environments. This article provides an overview of the basic physics of cool outflows, a comprehensive assessment of the observational techniques and diagnostic tools used to characterize them, a detailed description of the best-studied cases, and a more general discussion of the statistical properties of these outflows in the local and distant universe. The remaining outstanding issues that have not yet been resolved are summarized at the end of the review to inspire new research directions.

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Molecular gas in theHerschel-selected strongly lensed submillimeter galaxies atz ~ 2–4 as probed by multi-JCO lines

Yang

Omont

Beelen

et al. 2017

A&A

144

227

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We present the IRAM-30 m observations of multiple-J CO (J up mostly from 3 up to 8) and [C I]( 3 P 2 → 3 P 1 ) ([C I](2-1) hereafter) line emission in a sample of redshift ∼ 2-4 submillimeter galaxies (SMGs). These SMGs are selected among the brightest-lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Forty-seven CO lines and 7 [C I](2-1) lines have been detected in 15 lensed SMGs. A non-negligible effect of differential lensing is found for the CO emission lines, which could have caused significant underestimations of the linewidths, and hence of the dynamical masses. The CO spectral line energy distributions (SLEDs), peaking around J up ∼ 5-7, are found to be similar to those of the local starburst-dominated ultra-luminous infrared galaxies and of the previously studied SMGs. After correcting for lensing amplification, we derived the global properties of the bulk of molecular gas in the SMGs using non-LTE radiative transfer modelling, such as the molecular gas density n H 2 ∼ 10 2.5 -10 4.1 cm −3 and the kinetic temperature T k ∼ 20-750 K. The gas thermal pressure P th ranging from ∼ 10 5 K cm −3 to 10 6 K cm −3 is found to be correlated with star formation efficiency. Further decomposing the CO SLEDs into two excitation components, we find a low-excitation component with n H 2 ∼ 10 2.8 -10 4.6 cm −3 and T k ∼ 20-30 K, which is less correlated with star formation, and a high-excitation one (n H 2 ∼ 10 2.7 -10 4.2 cm −3 , T k ∼ 60-400 K) which is tightly related to the on-going star-forming activity. Additionally, tight linear correlations between the far-infrared and CO line luminosities have been confirmed for the J up ≥ 5 CO lines of these SMGs, implying that these CO lines are good tracers of star formation. The [C I](2-1) lines follow the tight linear correlation between the luminosities of the [C I](2-1) and the CO(1-0) line found in local starbursts, indicating that [C I] lines could serve as good total molecular gas mass tracers for high-redshift SMGs as well. The total mass of the molecular gas reservoir, (1-30) × 10 10 M , derived based on the CO(3-2) fluxes and α CO(1-0) = 0.8M ( K km s −1 pc 2 ) −1 , suggests a typical molecular gas depletion time t dep ∼ 20-100 Myr and a gas to dust mass ratio δ GDR ∼ 30-100 with ∼ 20%-60% uncertainty for the SMGs. The ratio between CO line luminosity and the dust mass L CO /M dust appears to be slowly increasing with redshift for high-redshift SMGs, which need to be further confirmed by a more complete SMG sample at various redshifts. Finally, through comparing the linewidth of CO and H 2 O lines, we find that they agree well in almost all our SMGs, confirming that the emitting regions of the CO and H 2 O lines are co-spatially located.

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Dusty Superwind from a Galaxy with a Compact Obscured Nucleus: Optical Spectroscopic Study of NGC 4418

Cited by 22 publications

References 117 publications

VV 655 and NGC 4418: Implications of an interaction for the evolution of a LIRG

VV 655 and NGC 4418: Implications of an interaction for the evolution of a LIRG

Cool outflows in galaxies and their implications

Molecular gas in theHerschel-selected strongly lensed submillimeter galaxies atz ~ 2–4 as probed by multi-JCO lines

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