ORCID Profile
0000-0003-0645-5260
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Astronomical and Space Sciences | Cosmology and Extragalactic Astronomy | Galactic Astronomy | Astroparticle physics and particle cosmology | Astronomical sciences | Cosmology and extragalactic astronomy | Astronomical and Space Instrumentation
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Publisher: American Astronomical Society
Date: 08-05-0006
Publisher: American Astronomical Society
Date: 05-02-2020
Publisher: American Astronomical Society
Date: 02-2022
Abstract: We present a case study of the stellar clumps in G04-1—a clumpy, turbulent disk galaxy located at z = 0.13—from the DYnamics of Newly-Assembled Massive Objects s le, using adaptive optics-enabled K -band imaging (∼2.25 kpc arcsec −1 ) with Keck-NIRC2. We identify 15 stellar clumps in G04-1 with a range of masses from 3.6 × 10 6 –2.7 × 10 8 M ⊙ , and a median mass of ∼ 2.9 × 10 7 M ⊙ . Note that these masses decrease by about half when we apply a light correction for the underlying stellar disk. A majority (12 of 15) of the clumps observed in the K P -band imaging have associated components in H α maps (∼2.75 kpc arcsec −1 R clump ∼ 500 pc) and appear colocated ( Δ x ¯ ∼ 0 .″ 1 ). Using Hubble Space Telescope observations from the Wide Field Camera on the Advanced Camera for Surveys, with the F336W and F467M filters, we also find evidence of radial trends in the stellar properties of the clumps: the clumps closer to the center of G04-1 are more massive (consistent with observations in high- z systems) and appear more red, suggesting they may be more evolved. Using our high-resolution data, we construct a star-forming main sequence for G04-1 in terms of spatially resolved quantities, and find that all regions (both clump and intraclump) within the galaxy are experiencing an enhanced mode of star formation routinely observed in galaxies at high- z . In comparison to recent simulations, our observations of a number of clumps with masses of 10 7 –10 8 M ⊙ are not consistent with strong radiative feedback in this galaxy.
Publisher: Oxford University Press (OUP)
Date: 20-05-2020
Abstract: We infer the intrinsic ionized gas kinematics for 383 star-forming galaxies across a range of integrated star formation rates (SFR ∈ [10−3, 102] M⊙ yr−1) at z ≲ 0.1 using a consistent 3D forward-modelling technique. The total s le is a combination of galaxies from the Sydney-AAO Multiobject Integral field Spectrograph (SAMI) Galaxy survey and DYnamics of Newly Assembled Massive Objects survey. For typical low-z galaxies taken from the SAMI Galaxy Survey, we find the vertical velocity dispersion (σv,z) to be positively correlated with measures of SFR, stellar mass, H i gas mass, and rotational velocity. The greatest correlation is with SFR surface density (ΣSFR). Using the total s le, we find σv,z increases slowly as a function of integrated SFR in the range SFR ∈ [10−3, 1] M⊙ yr−1 from 17 ± 3 to 24 ± 5 km s−1 followed by a steeper increase up to σv,z ∼80 km s−1 for SFR ≳ 1 M⊙ yr−1. This is consistent with recent theoretical models that suggest a σv,z floor driven by star formation feedback processes with an upturn in σv,z at higher SFR driven by gravitational transport of gas through the disc.
Publisher: American Astronomical Society
Date: 03-2021
Abstract: We compare the molecular and ionized gas velocity dispersions of nine nearby turbulent disks, analogs to high-redshift galaxies, from the DYNAMO s le using new Atacama Large Millimeter/submillimeter Array and GMOS/Gemini observations. We combine our s le with 12 galaxies at z ∼ 0.5–2.5 from the literature. We find that the resolved velocity dispersion is systematically lower by a factor 2.45 ± 0.38 for the molecular gas compared to the ionized gas, after correcting for thermal broadening. This offset is constant within the galaxy disks and indicates the coexistence of a thin molecular gas disk and a thick ionized one. This result has a direct impact on the Toomre Q and pressure derived in galaxies. We obtain pressures ∼0.22 dex lower on average when using the molecular gas velocity dispersion, σ 0,mol . We find that σ 0,mol increases with gas fraction and star formation rate. We also obtain an increase with redshift and show that the EAGLE and FIRE simulations overall overestimate σ 0,mol at high redshift. Our results suggest that efforts to compare the kinematics of gas using ionized gas as a proxy for the total gas may overestimate the velocity dispersion by a significant amount in galaxies at the peak of cosmic star formation. When using the molecular gas as a tracer, our s le is not consistent with predictions from star formation models with constant efficiency, even when including transport as a source of turbulence. Feedback models with variable star formation efficiency, ϵ ff , and/or feedback efficiency, p * / m * , better predict our observations.
Publisher: American Astronomical Society
Date: 04-04-2019
Publisher: American Astronomical Society
Date: 03-2023
Abstract: The spectral line energy distribution of carbon monoxide contains information about the physical conditions of the star-forming molecular hydrogen gas however, the relation to local radiation field properties is poorly constrained. Using ∼1–2 kpc scale Atacama Large Millimeter Array observations of CO(3−2) and CO(4−3), we characterize the CO(4−3)/CO(3−2) line ratios of local analogues of main-sequence galaxies at z ∼ 1–2, drawn from the DYnamics of Newly Assembled Massive Objects (DYNAMO) s le. We measure CO(4−3)/CO(3−2) across the disk of each galaxy and find a median line ratio of R 43 = 0.54 − 0.15 + 0.16 for the s le. This is higher than literature estimates of local star-forming galaxies and is consistent with multiple lines of evidence that indicate DYNAMO galaxies, despite residing in the local universe, resemble main-sequence galaxies at z ∼ 1–2. Comparing with existing lower-resolution CO(1−0) observations, we find R 41 and R 31 values in the range ∼0.2–0.3 and ∼0.4–0.8, respectively. We combine our kiloparsec-scale resolved line ratio measurements with Hubble Space Telescope observations of H α to investigate the relation to the star formation rate surface density and compare this relation to expectations from models. We find increasing CO(4−3)/CO(3−2) with increasing star formation rate surface density however, models overpredict the line ratios across the range of star formation rate surface densities we probe, in particular at the lower range. Finally, Stratospheric Observatory for Infrared Astronomy observations with the High-resolution Airborne Wideband Camera Plus and Field-Imaging Far-Infrared Line Spectrometer reveal low dust temperatures and no deficit of [C ii ] emission with respect to the total infrared luminosity.
Publisher: American Astronomical Society
Date: 30-08-2021
Publisher: Oxford University Press (OUP)
Date: 23-12-2019
Abstract: We present an analysis of the gas dynamics of star-forming galaxies at z ∼ 1.5 using data from the KMOS Galaxy Evolution Survey. We quantify the morphology of the galaxies using HSTcandels imaging parametrically and non-parametrically. We combine the H α dynamics from KMOS with the high-resolution imaging to derive the relation between stellar mass (M*) and stellar specific angular momentum (j*). We show that high-redshift star-forming galaxies at z ∼ 1.5 follow a power-law trend in specific stellar angular momentum with stellar mass similar to that of local late-type galaxies of the form j* ∝ M$_*^{0.53\\, \\pm \\, 0.10}$. The highest specific angular momentum galaxies are mostly disc-like, although generally both peculiar morphologies and disc-like systems are found across the sequence of specific angular momentum at a fixed stellar mass. We explore the scatter within the j* – M* plane and its correlation with both the integrated dynamical properties of a galaxy (e.g. velocity dispersion, Toomre Qg, H α star formation rate surface density ΣSFR) and its parametrized rest-frame UV / optical morphology (e.g. Sérsic index, bulge to total ratio, clumpiness, asymmetry, and concentration). We establish that the position in the j* – M* plane is strongly correlated with the star-formation surface density and the clumpiness of the stellar light distribution. Galaxies with peculiar rest-frame UV / optical morphologies have comparable specific angular momentum to disc- dominated galaxies of the same stellar mass, but are clumpier and have higher star formation rate surface densities. We propose that the peculiar morphologies in high-redshift systems are driven by higher star formation rate surface densities and higher gas fractions leading to a more clumpy interstellar medium.
Publisher: Oxford University Press (OUP)
Date: 25-02-2022
Abstract: We study star formation-driven outflows in a z ∼ 0.02 starbursting disc galaxy, IRAS08339+6517, using spatially resolved measurements from the Keck Cosmic Web Imager (KCWI). We develop a new method incorporating a multistep process to determine whether an outflow should be fit in each spaxel, and then subsequently decompose the emission line into multiple components. We detect outflows ranging in velocity, vout, from 100 to 600 km s−1 across a range of star formation rate surface densities, ΣSFR, from ∼0.01 to 10 M⊙ yr−1 kpc−2 in resolution elements of a few hundred parsec. Outflows are detected in ∼100 per cent of all spaxels within the half-light radius, and ∼70 per cent within r90, suggestive of a high covering fraction for this starbursting disc galaxy. Around 2/3 of the total outflowing mass originates from the star forming ring, which corresponds to ${\\lt}10{{\\ \\rm per\\ cent}}$ of the total area of the galaxy. We find that the relationship between vout and the ΣSFR, as well as between the mass loading factor, η, and the ΣSFR, are consistent with trends expected from energy-driven feedback models. We study the resolution effects on this relationship and find stronger correlations above a re-binned size-scale of ∼500 pc. Conversely, we do not find statistically significant consistency with the prediction from momentum-driven winds.
Publisher: American Astronomical Society
Date: 09-08-2017
Publisher: Oxford University Press (OUP)
Date: 25-09-2021
Abstract: We present detailed stellar specific angular momentum (j*) measurements of 10 star-forming galaxies at z ∼ 1.5−2, using both high and low spatial resolution integral field spectroscopic data. We developed a code that simultaneously models the adaptive optics (AO) assisted observations from OSIRIS/SINFONI along with their natural seeing (NS) counterparts from KMOS at spatial resolutions of [0.1−0.4] arcsec and [0.6−1.0] arcsec, respectively. The AO data reveal 2/10 systems to be mergers and for the remaining eight the mean uncertainties $\\bar{\\Delta }j_*$ decrease from 49 per cent (NS), and 26.5 per cent (AO), to 16 per cent in the combined analysis. These j* measurements agree within 20 per cent with simple estimates ($\\tilde{j_*}$) calculated from Hubble Space Telescope photometry and NS kinematics however, higher resolution kinematics are required to first identify these discs. We find that the choice of surface mass density model and the measurement of effective radius from photometry are the key sources of systematic effects in the measurement of j* between different analyses. Fitting the j* versus M* relations (Fall 1983) with a fixed power-law slope of β = 2/3, we find a zero-point consistent with prior NS results at z ≥ 1 within ∼0.3 dex. Finally, we find a ∼0.38 dex scatter about that relation that remains high despite the AO data so we conclude it is intrinsic to galaxies at z & 1. This compares to a scatter of ≤0.2 dex for discs at z ≃ 0 pointing to a settling of the Fall relation with cosmic time.
Publisher: American Astronomical Society
Date: 17-01-2012
Publisher: Oxford University Press (OUP)
Date: 21-08-2023
Publisher: American Astronomical Society
Date: 24-08-2016
Publisher: Oxford University Press (OUP)
Date: 20-04-2020
Abstract: We study the spatially resolved stellar specific angular momentum j* in a high-quality s le of 24 Calar Alto Legacy Integral Field Area galaxies covering a broad range of visual morphology, accounting for stellar velocity and velocity dispersion. The shape of the spaxelwise probability density function of normalized s = j*/j*mean, PDF(s), deviates significantly from the near-universal initial distribution expected of baryons in a dark matter halo and can be explained by the expected baryonic effects in galaxy formation that remove and redistribute angular momentum. Further we find that the observed shape of the PDF(s) correlates significantly with photometric morphology, where late-type galaxies have a PDF(s) that is similar to a normal distribution, whereas early types have a strongly skewed PDF(s) resulting from an excess of low-angular momentum material. Galaxies that are known to host pseudo-bulges (bulge Sérsic index nb & 2.2) tend to have less skewed bulge PDF(s), with skewness (b1rb) ≲ 0.8. The PDF(s) encodes both kinematic and photometric information and appears to be a robust tracer of morphology. Its use is motivated by the desire to move away from traditional component-based classifications which are subject to observer bias, to classification on a galaxy’s fundamental (stellar mass and angular momentum) properties. In future, PDF(s) may also be useful as a kinematic decomposition tool.
Publisher: Oxford University Press (OUP)
Date: 06-07-2020
Abstract: We present results from the KMOS Lens-Amplified Spectroscopic Survey (KLASS), an ESO Very Large Telescope (VLT) large program using gravitational lensing to study the spatially resolved kinematics of 44 star-forming galaxies at 0.6 & z & 2.3 with a stellar mass of 8.1 & log(M⋆/M⊙) & 11.0. These galaxies are located behind six galaxy clusters selected from the Hubble Space Telescope Grism Lens-Amplified Survey from Space (GLASS). We find that the majority of the galaxies show a rotating disc, but most of the rotation-dominated galaxies only have a low υ rot/σ0 ratio (median of υrot/σ0 ∼ 2.5). We explore the Tully–Fisher relation by adopting the circular velocity, $V_{\\mathrm{ circ}}=(\\upsilon _{\\mathrm{ rot}}^2+3.4\\sigma _0^2)^{1/2}$, to account for pressure support. We find that our s le follows a Tully–Fisher relation with a positive zero-point offset of +0.18 dex compared to the local relation, consistent with more gas-rich galaxies that still have to convert most of their gas into stars. We find a strong correlation between the velocity dispersion and stellar mass in the KLASS s le. When combining our data to other surveys from the literature, we see an increase of the velocity dispersion with stellar mass at all redshift. We obtain an increase of υrot/σ0 with stellar mass at 0.5 & z & 1.0. This could indicate that massive galaxies settle into regular rotating discs before the low-mass galaxies. For higher redshift (z & 1), we find a weak increase or flat trend. We find no clear trend between the rest-frame UV clumpiness and the velocity dispersion and υrot/σ0. This could suggest that the kinematic properties of galaxies evolve after the clumps formed in the galaxy disc or that the clumps can form in different physical conditions.
Publisher: Oxford University Press (OUP)
Date: 06-09-2023
Publisher: Springer Science and Business Media LLC
Date: 25-05-2020
Publisher: American Astronomical Society
Date: 04-2022
Abstract: We report on the internal distribution of star formation efficiency in IRAS 08339+6517 (hereafter IRAS08), using ∼200 pc resolution CO(2 − 1) observations from NOEMA. The molecular gas depletion time changes by 2 orders-of-magnitude from disk-like values in the outer parts to less than 10 8 yr inside the half-light radius. This translates to a star formation efficiency per freefall time that also changes by 2 orders-of-magnitude, reaching 50%–100%, different than local spiral galaxies and the typical assumption of constant, low star formation efficiencies. Our target is a compact, massive disk galaxy that has a star formation rate 10× above the z = 0 main sequence Toomre Q ≈ 0.5−0.7 and high gas velocity dispersion ( σ mol ≈ 25 km s −1 ). We find that IRAS08 is similar to other rotating, starburst galaxies from the literature in the resolved Σ SFR ∝ Σ mol N relation. By combining resolved literature studies we find that the distance from the main sequence is a strong indicator of the Kennicutt-Schmidt power-law slope, with slopes of N ≈ 1.6 for starbursts from 100 to 10 4 M ⊙ pc −2 . Our target is consistent with a scenario in which violent disk instabilities drive rapid inflows of gas. It has low values of Toomre- Q , and also at all radii, the inflow timescale of the gas is less than the depletion time, which is consistent with the flat metallicity gradients in IRAS08. We consider these results in light of popular star formation theories in general observations of IRAS08 find the most tension with theories in which star formation efficiency is a constant. Our results argue for the need of high-spatial-resolution CO observations for a larger number of similar targets.
Publisher: Oxford University Press (OUP)
Date: 14-09-2017
Publisher: American Astronomical Society
Date: 14-12-2015
Publisher: Oxford University Press (OUP)
Date: 15-03-2019
DOI: 10.1093/MNRAS/STZ765
Publisher: Wiley
Date: 26-09-2022
DOI: 10.1002/ANA.26493
Abstract: Seizures are more common in the neonatal period than at any other stage of life. Phenobarbital is the first‐line treatment for neonatal seizures and is at best effective in approximately 50% of babies, but may contribute to neuronal injury. Here, we assessed the efficacy of phenobarbital versus the synthetic neurosteroid, ganaxolone, to moderate seizure activity and neuropathology in neonatal lambs exposed to perinatal asphyxia. Asphyxia was induced via umbilical cord occlusion in term lambs at birth. Lambs were treated with ganaxolone (5mg/kg/bolus then 5mg/kg/day for 2 days) or phenobarbital (20mg/kg/bolus then 5mg/kg/day for 2 days) at 6 hours. Abnormal brain activity was classified as stereotypic evolving (SE) seizures, epileptiform discharges (EDs), and epileptiform transients (ETs) using continuous litude‐integrated electroencephalographic recordings. At 48 hours, lambs were euthanized for brain pathology. Asphyxia caused abnormal brain activity, including SE seizures that peaked at 18 to 20 hours, EDs, and ETs, and induced neuronal degeneration and neuroinflammation. Ganaxolone treatment was associated with an 86.4% reduction in the number of seizures compared to the asphyxia group. The total seizure duration in the asphyxia+ganaxolone group was less than the untreated asphyxia group. There was no difference in the number of SE seizures between the asphyxia and asphyxia+phenobarbital groups or duration of SE seizures. Ganaxolone treatment, but not phenobarbital, reduced neuronal degeneration within hippoc al CA1 and CA3 regions, and cortical neurons, and ganaxolone reduced neuroinflammation within the thalamus. Ganaxolone provided better seizure control than phenobarbital in this perinatal asphyxia model and was neuroprotective for the newborn brain, affording a new therapeutic opportunity for treatment of neonatal seizures. ANN NEUROL 2022 :1066–1079
Publisher: American Astronomical Society
Date: 17-11-2017
Publisher: Oxford University Press (OUP)
Date: 14-03-2019
DOI: 10.1093/MNRAS/STZ750
Publisher: Oxford University Press (OUP)
Date: 30-06-2014
Publisher: American Astronomical Society
Date: 09-10-2013
Publisher: Springer Science and Business Media LLC
Date: 19-12-2016
Publisher: American Astronomical Society
Date: 06-04-2017
Publisher: Oxford University Press (OUP)
Date: 21-08-2023
Publisher: American Astronomical Society
Date: 18-07-2014
Publisher: Oxford University Press (OUP)
Date: 09-03-2022
Abstract: In this paper, we use Hubble Space Telescope/WFC3 observations of six galaxies from the DYnamics of Newly Assembled Massive Object (DYNAMO) survey, combined with stellar population modelling of the SED, to determine the stellar masses of DYNAMO clumps. The DYNAMO s le has been shown to have properties similar to z ≈ 1.5 turbulent, clumpy discs. DYNAMO s le clump masses offer a useful comparison for studies of z & 1 in that the galaxies have the same properties, yet the observational biases are significantly different. Using DYNAMO, we can more easily probe rest-frame near-IR wavelengths and also probe finer spatial scales. We find that the stellar mass of DYNAMO clumps is typically 107−108M⊙. We employ a technique that makes non-parametric corrections in removal of light from nearby clumps, and carries out a locally determined disc subtraction. The process of disc subtraction is the dominant effect, and can alter clump masses at the 0.3 dex level. Using these masses, we investigate the stellar mass function (MF) of clumps in DYNAMO galaxies. DYNAMO stellar MFs follow a declining power law with slope α ≈ −1.4, which is slightly shallower than, but similar to what is observed in z & 1 lensed galaxies. We compare DYNAMO clump masses to results of simulations. The masses and galactocentric position of clumps in DYNAMO galaxies are more similar to long-lived clumps in simulations. Similar to recent DYNAMO results on the stellar population gradients, these results are consistent with simulations that do not employ strong ‘early’ radiative feedback prescriptions.
Publisher: American Astronomical Society
Date: 12-2022
Abstract: We compare 500 pc scale, resolved observations of ionized and molecular gas for the z ∼ 0.02 starbursting disk galaxy IRAS08339+6517, using measurements from KCWI and NOEMA. We explore the relationship of the star-formation-driven ionized gas outflows with colocated galaxy properties. We find a roughly linear relationship between the outflow mass flux ( Σ ̇ out ) and star formation rate surface density (Σ SFR ), Σ ̇ out ∝ Σ SFR 1.06 ± 0.10 , and a strong correlation between Σ ̇ out and the gas depletion time, such that Σ ̇ out ∝ t dep − 1.1 ± 0.06 . Moreover, we find these outflows are so-called breakout outflows, according to the relationship between the gas fraction and disk kinematics. Assuming that ionized outflow mass scales with total outflow mass, our observations suggest that the regions of highest Σ SFR in IRAS08 are removing more gas via the outflow than through the conversion of gas into stars. Our results are consistent with a picture in which the outflow limits the ability of a region of a disk to maintain short depletion times. Our results underline the need for resolved observations of outflows in more galaxies.
Publisher: American Astronomical Society
Date: 04-01-2019
Publisher: American Astronomical Society
Date: 29-08-2017
Publisher: Oxford University Press (OUP)
Date: 10-11-2019
Publisher: Springer Science and Business Media LLC
Date: 07-2013
DOI: 10.1038/NATURE12351
Abstract: The under-abundance of very massive galaxies in the Universe is frequently attributed to the effect of galactic winds. Although ionized galactic winds are readily observable, most of the expelled mass (that is, the total mass flowing out from the nuclear region) is likely to be in atomic and molecular phases that are cooler than the ionized phases. Expanding molecular shells observed in starburst systems such as NGC 253 (ref. 12) and M 82 (refs 13, 14) may facilitate the entrainment of molecular gas in the wind. Although shell properties are well constrained, determining the amount of outflowing gas emerging from such shells and the connection between this gas and the ionized wind requires spatial resolution better than 100 parsecs coupled with sensitivity to a wide range of spatial scales, a combination hitherto not available. Here we report observations of NGC 253, a nearby starburst galaxy (distance ∼ 3.4 megaparsecs) known to possess a wind, that trace the cool molecular wind at 50-parsec resolution. At this resolution, the extraplanar molecular gas closely tracks the Hα filaments, and it appears to be connected to expanding molecular shells located in the starburst region. These observations allow us to determine that the molecular outflow rate is greater than 3 solar masses per year and probably about 9 solar masses per year. This implies a ratio of mass-outflow rate to star-formation rate of at least 1, and probably ∼3, indicating that the starburst-driven wind limits the star-formation activity and the final stellar content.
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Start Date: 09-2017
End Date: 08-2023
Amount: $680,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2023
End Date: 12-2025
Amount: $660,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2016
End Date: 03-2020
Amount: $560,800.00
Funder: Australian Research Council
View Funded ActivityStart Date: 11-2022
End Date: 12-2023
Amount: $1,749,940.00
Funder: Australian Research Council
View Funded ActivityStart Date: 07-2017
End Date: 12-2024
Amount: $30,300,000.00
Funder: Australian Research Council
View Funded Activity