We present a detailed analysis of the ionized gas distribution and kinematics in the inner ∼ 200 pc of NGC 4546, host of a low-luminosity active galactic nucleus (LLAGN). Using GMOS−IFU observations, with a spectral coverage of 4736–6806 Å and an angular resolution of 0.7 arcsec, we confirm that the nuclear emission is consistent with photoionization by an AGN, while the gas in the circumnuclear region may be ionized by hot low-mass evolved stars. The gas kinematics in the central region of NGC 4546 presents three components: (i) a disc with major axis oriented along a position angle of 43° ± 3°, counter rotating relative to the stellar disc; (ii) non-circular motions, evidenced by residual velocities of up to 60 km s−1, likely associated with a previous capture of a dwarf satellite by NGC 4546; and (iii) nuclear outflows in ionized gas, identified as a broad component (σ ∼ 320 km s−1) in the line profiles, with a mass outflow rate of $\dot{M}_{\rm out} = 0.3 \pm 0.1$ M⊙ yr−1 and a total mass of Mout = (9.2 ± 0.8) × 103 M⊙ in ionized gas, corresponding to less than 3 per cent of the total mass of ionized gas in the inner 200 pc of NGC 4546. The kinetic efficiency of the outflow is roughly 0.1 per cent, which is smaller than the outflow coupling efficiencies predicted by theoretical studies to AGN feedback become efficient in suppressing star formation in the host galaxy.
- Award ID(s):
- 1757321
- NSF-PAR ID:
- 10226280
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- ISSN:
- 0035-8711
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
ABSTRACT -
more » « less
Abstract The dwarf galaxy Triangulum (M33) presents an interesting testbed for studying stellar halo formation: it is sufficiently massive so as to have likely accreted smaller satellites, but also lies within the regime where feedback and other “in situ” formation mechanisms are expected to play a role. In this work, we analyze the line-of-sight kinematics of stars across M33 from the TREX survey, with a view to understanding the origin of its halo. We split our sample into two broad populations of varying age, comprising 2032 “old” red giant branch stars and 671 “intermediate-age” asymptotic giant branch and carbon stars. We find decisive evidence for two distinct kinematic components in both the old and intermediate-age populations: a low-dispersion (∼22 km s−1) disk-like component corotating with M33's H
i gas and a significantly higher-dispersion component (∼50–60 km s−1) that does not rotate in the same plane as the gas and is thus interpreted as M33's stellar halo. While kinematically similar, the fraction of stars associated with the halo component differs significantly between the two populations: this is consistently ∼10% for the intermediate-age population, but decreases from ∼34% to ∼10% as a function of radius for the old population. We additionally find evidence that the intermediate-age halo population is systematically offset from the systemic velocity of M33 by ∼25 km s−1, with a preferred central LOS velocity of ∼ − 155 km s−1. This is the first detection and characterization of an intermediate-age halo in M33, and suggests in situ formation mechanisms, as well as potentially tidal interactions, have helped shaped it. -
more » « less
ABSTRACT Counter-rotating components in galaxies are one of the most direct forms of evidence for past gas accretion or merging. We discovered 10 edge-on disc gaseous counter-rotators in a sample of 523 edge-on galaxies identified in the final MaNGA (Mapping Nearby Galaxies at APO) IFU sample. The counter-rotators tend to located in small groups. The gaseous counter-rotators have intermediate stellar masses and and located in the green valley and red sequence of the colour–magnitude diagram. The average vertical extents of the stellar and ionized gas discs are the same as for the rest of the sample while their radial gas and stellar distributions are more centrally concentrated. This may point at angular momentum loss during the formation process of the counter-rotating discs. The counter-rotators have low gas and dust content, weak emission-line strengths, and low star formation rates. This suggests that the formation of counter-rotators may be an efficient way to quench galaxies. One counter-rotator, SDSS J080016.09+292817.1 (Galaxy F), has a post-starburst region and a possible AGN at the centre. Another counter-rotator, SDSS J131234.03+482159.8 (Galaxy H), is identified as a potential ongoing galaxy interaction with its companion satellite galaxy, a gas-rich spiral galaxy. This may be representative case of a gaseous counter-rotator forming through a merger origin. However, tidal distortions expected in mergers are only found in a few of the galaxies and we cannot rule out direct gas accretion as another formation mechanism.
-
more » « less
ABSTRACT The processes responsible for the assembly of cold and warm gas in early-type galaxies (ETGs) are not well understood. We report on the multiwavelength properties of 15 non-central, nearby (z ≤ 0.008 89) ETGs primarily through Multi-Unit Spectroscopic Explorer (MUSE) and Chandra X-ray observations, to address the origin of their multiphase gas. The MUSE data reveal that 8/15 sources contain warm ionized gas traced by the H α emission line. The morphology of this gas is found to be filamentary in 3/8 sources: NGC 1266, NGC 4374, and NGC 4684, which is similar to that observed in many group and cluster-centred galaxies. All H α filamentary sources have X-ray luminosities exceeding the expected emission from the stellar population, suggesting the presence of diffuse hot gas, which likely cooled to form the cooler phases. The morphologies of the remaining 5/8 sources are rotating gas discs, not as commonly observed in higher mass systems. Chandra X-ray observations (when available) of the ETGs with rotating H α discs indicate that they are nearly void of hot gas. A mixture of stellar mass-loss and external accretion was likely the dominant channel for the cool gas in NGC 4526 and NGC 4710. These ETGs show full kinematic alignment between their stars and gas, and are fast rotators. The H α features within NGC 4191 (clumpy, potentially star-forming ring), NGC 4643, and NGC 5507 (extended structures) along with loosely overlapping stellar and gas populations allow us to attribute external accretion to be the primary formation channel of their cool gas.
-
more » « less
ABSTRACT We report a tentative detection of the circumgalactic medium (CGM) of Wolf–Lundmark–Melotte (WLM), an isolated, low-mass (logM*/M⊙ ≈ 7.6), dwarf irregular galaxy in the Local Group (LG). We analyse an HST/COS archival spectrum of a quasar sightline (PHL2525), which is 45 kpc (0.5 virial radius) from WLM and close to the Magellanic Stream (MS). Along this sightline, two ion absorbers are detected in Si ii, Si iii, Si iv, C ii, and C iv at velocities of ∼−220 km s−1 (Component v-220) and ∼−150 km s−1 (Component v-150). To identify their origins, we study the position–velocity alignment of the components with WLM and the nearby MS. Near the magellanic longitude of PHL2525, the MS-related neutral and ionized gas moves at ≲−190 km s−1, suggesting an MS origin for Component v-220, but not for Component v-150. Because PHL2525 passes near WLM and Component v-150 is close to WLM’s systemic velocity (∼−132 km s−1), it is likely that Component v-150 arises from the galaxy’s CGM. This results in a total Si mass in WLM’s CGM of $M_{\rm Si}^{\rm CGM}\sim (0.2-1.0)\times 10^5~\mathrm{M}_\odot$ using assumption from other COS dwarf studies. Comparing $M_{\rm Si}^{\rm CGM}$ to the total Si mass synthesized in WLM over its lifetime (∼1.3 × 105 M⊙), we find ∼3 per cent is locked in stars, ∼6 per cent in the ISM, ∼15–77 per cent in the CGM, and the rest (∼14–76 per cent) is likely lost beyond the virial radius. Our finding resonates with other COS dwarf galaxy studies and theoretical predictions that low-mass galaxies can easily lose metals into their CGM due to stellar feedback and shallow gravitational potential.
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/mnras/stab1137
