The interplay between feedback, accretion, transport and winds in setting gas-phase metal distribution in galaxies

The recent decade has seen an exponential growth in spatially-resolved metallicity measurements in the interstellar medium (ISM) of galaxies. To first order, these measurements are characterised by the slope of the radial metallicity profile, known as the metallicity gradient. In this work, we model the relative role of star formation feedback, gas transport, cosmic gas accretion, and galactic winds in driving radial metallicity profiles and setting the mass-metallicity gradient relation (MZGR). We include a comprehensive treatment of these processes by including them as sources that supply mass, metals, and energy to marginally unstable galactic discs in pressure and energy balance. We show that both feedback and accretion that can drive turbulence and enhance metal-mixing via diffusion are crucial to reproduce the observed MZGR in local galaxies. Metal transport also contributes to setting metallicity profiles, but it is sensitive to the strength of radial gas flows in galaxies. While the mass loading of galactic winds is important to reproduce the mass metallicity relation (MZR), we find that metal mass loading is more important to reproducing the MZGR. Specifically, our model predicts preferential metal enrichment of galactic winds in low-mass galaxies. This conclusion is robust against our adopted scaling of the wind mass-loading factor, uncertainties in measured wind metallicities, and systematics due to metallicity calibrations. Overall, we find that at $z \sim 0$, galactic winds and metal transport are more important in setting metallicity gradients in low-mass galaxies whereas star formation feedback and gas accretion dominate setting metallicity gradients in massive galaxies.Comment: 20 pages (+ appendix), 11 figures, 4 tables. Submitted to MNRA

The SAMI Galaxy Survey: impact of black hole activity on galaxy spin-filament alignments

The activity of central supermassive black holes might affect the alignment of galaxy spin axes with respect to the closest cosmic filaments. We exploit the SAMI Galaxy Survey to study possible relations between black hole activity and the spin-filament alignments of stars and ionised gas separately. To explore the impact of instantaneous black hole activity, active galaxies are selected according to emission-line diagnostics. Central stellar velocity dispersion ($\sigma_c$) is used as a proxy for black hole mass and its integrated activity. We find evidence for the gas spin-filament alignments to be influenced by AGN, with Seyfert galaxies showing a stronger perpendicular alignment at fixed bulge mass with respect to galaxies where ionisation is consequence of low-ionizaition nuclear emission-line regions (LINERs) or old stellar populations (retired galaxies). On the other hand, the greater perpendicular tendency for the stellar spin-filament alignments of high-bulge mass galaxies is dominated by retired galaxies. Stellar alignments show a stronger correlation with $\sigma_c$ compared to the gas alignments. We confirm that bulge mass ($M_{bulge}$) is the primary parameter of correlation for both stellar and gas spin-filament alignments (with no residual dependency left for $\sigma_c$), while $\sigma_c$ is the most important property for secular star formation quenching (with no residual dependency left for $M_{bulge}$). These findings indicate that $M_{bulge}$ and $\sigma_c$ are the most predictive parameters of two different galaxy evolution processes, suggesting mergers trigger spin-filament alignment flips and integrated black hole activity drives star formation quenching.Comment: 20 pages, 16 figures, accepted for publication in MNRA

Beyond BPT: A New Multi-Dimensional Diagnostic Diagram for Classifying Power Sources Tested Using the SAMI Galaxy Survey

Current methods of identifying the ionizing source of nebular emission in galaxies are well defined for the era of single fiber spectroscopy, but still struggle to differentiate the complex and overlapping ionization sources in some galaxies. With the advent of integral field spectroscopy, the limits of these previous classification schemes are more apparent. We propose a new method for distinguishing the ionizing source in resolved galaxy spectra by use of a multi-dimensional diagnostic diagram that compares emission line ratios with velocity dispersion on a spaxel by spaxel basis within a galaxy. This new method is tested using the SAMI Galaxy Survey Data Release 3, which contains 3068 galaxies at z $<$ 0.12. Our results are released as ionization maps available alongside the SAMI DR3 public data. Our method accounts for a more diverse range of ionization sources than the standard suite of emission line diagnostics; we find 1433 galaxies with significant contribution from non-star-forming ionization using our improved method as compared to 316 galaxies identified using only emission line ratio diagnostics. Within these galaxies, we further identify 886 galaxies hosting unique signatures inconsistent with standard ionization by H2 regions, AGN, or shocks. These galaxies span a wide range of masses and morphological types and comprise a sizable portion of the galaxies used in our sample. With our revised method, we show that emission line diagnostics alone do not adequately differentiate the multiple ways to ionize gas within a galaxy

Cryogenic detector preamplifer developments at the ANU

We present a summary of the cryogenic detector preamplifier development programme under way at the ANU. Cryogenic preamplifiers have been demonstrated for both near-infrared detectors (Teledyne H1RG and Leonardo SAPHIRA eAPD as part of development for the GMTIFS instrument) and optical CCDs (e2v CCD231-84 for use with the AAT/Veloce spectrograph). This approach to detector signal conditioning allows low-noise instrument amplifiers to be placed very close to an infra-red detector or optical CCD, isolating the readout path from external interference noise sources. Laboratory results demonstrate effective isolation of the readout path from external interference noise sources. Recent progress has focussed on the first on-sky deployment of four cryogenic preamp channels for the Veloce Rosso precision radial velocity spectrograph. We also outline future evolution of the current design, allowing higher speeds and further enhanced performance for the demanding applications required for the on instrument wavefront sensor on the Giant Magellan Integral Field Spectrograph (GMTIFS).This research was supported under Australian Research Council's Linkage Project funding scheme (LP150100620) in partnership with the Australian National University and Giant Magellan Telescope Organisation

Resolving Jet-Driven Feedback on Sub-kpc Scales

Relativistic jets from active galactic nuclei are known to have a profound impact on their environment, both enhancing ('positive feedback') and inhibiting ('negative feedback') star formation under certain conditions. However, the role that these feedback processes play in shaping the properties of their host galaxies and environment remains elusive. In particular, efforts to catch feedback 'in the act' have been hampered by the spatial resolution required to resolve the jets' environment. In this thesis, I advance our understanding of jet-driven feedback by comparing hydrodynamical simulations to high angular resolution optical and near-infrared integral field spectroscopy (IFS) observations, which allow us to probe the critical sub-kpc scales necessary to bridge the gap between theory and observations. To investigate feedback processes driven by young jets, I led observational programs focusing on the local radio galaxies 4C 31.04 and UGC 05771. Both galaxies harbour young jets confined to the interstellar medium (ISM), with very long baseline interferometry (VLBI) revealing jets ~100 pc and ~10 pc in size in 4C 31.04 and UGC 05771 respectively. Using adaptive optics-assisted near-infrared IFS from Gemini/NIFS and Keck/OSIRIS, I found signatures of jet-ISM interactions at radii up to 100 times larger than the size of the jets in both galaxies, a surprising result which indicated the existence of low surface-brightness jet plasma not visible in the VLBI observations. This is consistent with contemporary hydrodynamical simulations which show that the main jet streams may become temporarily halted by dense clumps in the ISM, whilst secondary plasma streams - which have a much lower surface brightness - can percolate through channels in the ISM, reaching much larger radii. The fact that this phenomenon was observed in both galaxies suggests it may be common in young radio galaxies, and may regulate star formation by driving shocks into the ISM. To investigate jet-induced star formation, I led a study of Minkowski's Object, a peculiar star-forming dwarf galaxy located in the path of the radio jet from the galaxy NGC 541 in the nearby cluster Abell 194. I carried out an IFS study of this enigmatic object using WiFeS on the ANU 2.3 m telescope, and determined that the observed emission line ratios are consistent with star formation, with a minor contribution from non-stellar ionisation sources, and an unusually large metallicity variation within the object, the origin of which remains unclear

Searching for signs of jet-driven negative feedback in the nearby radio galaxy UGC 05771

International audienc

Jets blowing bubbles in the young radio galaxy 4C 31.04

International audienceWe report the discovery of shocked molecular and ionized gas resulting from jet-driven feedback in the low-redshift (z = 0.0602) compact radio galaxy 4C 31.04 using near-IR imaging spectroscopy. 4C 31.04 is a ˜100 pc double-lobed Compact Steep Spectrum source believed to be a very young active galactic nucleus (AGN). It is hosted by a giant elliptical with a ˜ 109 M_⊙ multiphase gaseous circumnuclear disc. We used high spatial resolution, adaptive optics-assisted H- and K-band integral field Gemini/NIFS observations to probe (1) the warm (˜103 K) molecular gas phase, traced by ro-vibrational transitions of H2, and (2), the warm ionized medium, traced by the [Fe II]_{1.644 μ m} line. The [Fe II] emission traces shocked gas ejected from the disc plane by a jet-blown bubble 300-400 pc in diameter, while the H2 emission traces shock-excited molecular gas in the interior ˜ 1 kpc of the circumnuclear disc. Hydrodynamical modelling shows that the apparent discrepancy between the extent of the shocked gas and the radio emission can occur when the brightest regions of the synchrotron-emitting plasma are temporarily halted by dense clumps, while less bright plasma can percolate through the porous ISM and form an energy-driven bubble that expands freely out of the disc plane. Simulations suggest that this bubble is filled with low surface brightness plasma not visible in existing VLBI observations of 4C 31.04 due to insufficient sensitivity. Additional radial flows of jet plasma may percolate to ˜ kpc radii in the circumnuclear disc, driving shocks and accelerating clouds of gas, giving rise to the H2 emission

Jets blowing bubbles in the young radio galaxy 4C 31.04

International audienceWe report the discovery of shocked molecular and ionized gas resulting from jet-driven feedback in the low-redshift (z = 0.0602) compact radio galaxy 4C 31.04 using near-IR imaging spectroscopy. 4C 31.04 is a ∼100 pc double-lobed Compact Steep Spectrum source believed to be a very young active galactic nucleus (AGN). It is hosted by a giant elliptical with a |${\sim } 10^{9}\, \rm M_\odot$| multiphase gaseous circumnuclear disc. We used high spatial resolution, adaptive optics-assisted H- and K-band integral field Gemini/NIFS observations to probe (1) the warm (∼10^3 K) molecular gas phase, traced by ro-vibrational transitions of H_2, and (2), the warm ionized medium, traced by the [Fe ii]|$_{1.644\, \rm \mu m}$| line. The [Fe ii] emission traces shocked gas ejected from the disc plane by a jet-blown bubble |$300\!-\!400\, \rm pc$| in diameter, while the H_2 emission traces shock-excited molecular gas in the interior |${\sim } 1\, \rm kpc$| of the circumnuclear disc. Hydrodynamical modelling shows that the apparent discrepancy between the extent of the shocked gas and the radio emission can occur when the brightest regions of the synchrotron-emitting plasma are temporarily halted by dense clumps, while less bright plasma can percolate through the porous ISM and form an energy-driven bubble that expands freely out of the disc plane. Simulations suggest that this bubble is filled with low surface brightness plasma not visible in existing VLBI observations of 4C 31.04 due to insufficient sensitivity. Additional radial flows of jet plasma may percolate to ∼ kpc radii in the circumnuclear disc, driving shocks and accelerating clouds of gas, giving rise to the H_2 emission

Revisiting the giant radio galaxy ESO 422-G028 - I. Discovery of a neutral inflow and recent star formation in a restarted giant

International audienceGiant radio galaxies provide important clues into the life cycles and triggering mechanisms of radio jets. With large-scale jets spanning 1.8 Mpc, ESO 422-G028 (z = 0.038) is a giant radio galaxy that also exhibits signs of restarted jet activity in the form of pc-scale jets. We present a study of the spatially resolved stellar and gas properties of ESO 422-G028 using optical integral field spectroscopy from the Wide-Field Spectrograph (WiFeS). In addition to the majority ${\sim} 13\, \rm Gyr$ old stellar population, ESO 422-G028 exhibits a much younger (${\lesssim} 10\, \rm Myr$ old) component with an estimated mass of $10^{7.6}\, \rm M_\odot$ that is predominantly located in the north-west region of the galaxy. Unusually, the ionized gas kinematics reveal two distinct discs traced by narrow ($\sigma _{\rm H\alpha } 100 \, \rm km\, s^{-1}$) and broad ($\sigma _{\rm H\alpha } 150 \, \rm km\, s^{-1}$) Hα emission, respectively. Both ionized gas discs are misaligned with the axis of stellar rotation, suggesting an external origin. This is consistent with the prominent interstellar Na D absorption, which traces a $1 \!-\! 3 \, \rm M_\odot \, yr^{-1}$ inflow of neutral gas from the north. We posit that an inflow of gas - either from an accretion event or a gas-rich merger - has triggered both the starburst and the restarted jet activity, and that ESO 422-G028 is potentially on the brink of an epoch of powerful active galactic nucleus (AGN) activity

Unravelling the enigmatic ISM conditions in Minkowski's Object

22 pages, 18 figures. Accepted to the Monthly Notices of the Royal Astronomical SocietyInternational audienceLocal examples of jet-induced star formation lend valuable insight into its significance in galaxy evolution and can provide important observational constraints for theoretical models of positive feedback. Using optical integral field spectroscopy, we present an analysis of the ISM conditions in Minkowski's Object ($z = 0.0189$), a peculiar star-forming dwarf galaxy located in the path of a radio jet from the galaxy NGC 541. Full spectral fitting with PPXF indicates that Minkowski's Object primarily consists of a young stellar population $\sim 10$ Myr old, confirming that the bulk of the object's stellar mass formed during a recent jet interaction. Minkowski's Object exhibits line ratios largely consistent with star formation, although there is evidence for a low level ($\lesssim 15$ per cent) of contamination from a non-stellar ionising source. Strong-line diagnostics reveal a significant variation in the gas-phase metallicity within the object, with $\log\left( \rm O / H \right) + 12$ varying by $\sim 0.5$ dex, which cannot be explained by in-situ star formation, an enriched outflow from the jet, or enrichment of gas in the stellar bridge between NGC 541 and NGC 545/547. We hypothesise that Minkowski's Object either (a) was formed as a result of jet-induced star formation in pre-existing gas clumps in the stellar bridge, or (b) is a gas-rich dwarf galaxy that is experiencing an elevation in its star formation rate due to a jet interaction, and will eventually redden and fade, becoming an ultra-diffuse galaxy as it is processed by the cluster