ORCID Profile
0000-0002-8583-2521
Current Organisation
Swinburne University of Technology
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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: Oxford University Press (OUP)
Date: 20-09-2019
Abstract: SIGNALS, the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey, is a large observing programme designed to investigate massive star formation and H ii regions in a s le of local extended galaxies. The programme will use the imaging Fourier transform spectrograph SITELLE at the Canada–France–Hawaii Telescope. Over 355 h (54.7 nights) have been allocated beginning in fall 2018 for eight consecutive semesters. Once completed, SIGNALS will provide a statistically reliable laboratory to investigate massive star formation, including over 50 000 resolved H ii regions: the largest, most complete, and homogeneous data base of spectroscopically and spatially resolved extragalactic H ii regions ever assembled. For each field observed, three datacubes covering the spectral bands of the filters SN1 (363–386 nm), SN2 (482–513 nm), and SN3 (647–685 nm) are gathered. The spectral resolution selected for each spectral band is 1000, 1000, and 5000, respectively. As defined, the project s le will facilitate the study of small-scale nebular physics and many other phenomena linked to star formation at a mean spatial resolution of ∼20 pc. This survey also has considerable legacy value for additional topics, including planetary nebulae, diffuse ionized gas, and supernova remnants. The purpose of this paper is to present a general outlook of the survey, notably the observing strategy, galaxy s le, and science requirements.
Publisher: EDP Sciences
Date: 05-2018
DOI: 10.1051/0004-6361/201731988
Abstract: We present results from the KMOS LENsing Survey (KLENS), which is exploiting gravitational lensing to study the kinematics of 24 star-forming galaxies at 1.4 z 3.5 with a median mass of log( M ⋆ ∕ M ⊙ ) = 9.6 and a median star formation rate (SFR) of 7.5 M ⊙ yr −1 . We find that 25% of these low mass/low SFR galaxies are rotation-dominated, while the majority of our s le shows no velocity gradient. When combining our data with other surveys, we find that the fraction of rotation-dominated galaxies increases with the stellar mass, and decreases for galaxies with a positive offset from the main sequence (higher specific star formation rate). We also investigate the evolution of the intrinsic velocity dispersion, σ 0 , as a function of the redshift, z , and stellar mass, M ⋆ , assuming galaxies in quasi-equilibrium (Toomre Q parameter equal to 1). From the z − σ 0 relation, we find that the redshift evolution of the velocity dispersion is mostly expected for massive galaxies (log( M ⋆ ∕ M ⊙ ) 10). We derive a M ⋆ − σ 0 relation, using the Tully–Fisher relation, which highlights that a different evolution of the velocity dispersion is expected depending on the stellar mass, with lower velocity dispersions for lower masses, and an increase for higher masses, stronger at higher redshift. The observed velocity dispersions from this work and from comparison s les spanning 0 z 3.5 appear to follow this relation, except at higher redshift ( z 2), where we observe higher velocity dispersions for low masses (log( M ⋆ ∕ M ⊙ ) ~ 9.6) and lower velocity dispersions for high masses (log( M ⋆ ∕ M ⊙ ) ~ 10.9) than expected. This discrepancy could, for instance, suggest that galaxies at high redshift do not satisfy the stability criterion, or that the adopted parametrization of the specific star formation rate and molecular properties fail at high redshift.
Publisher: Elsevier BV
Date: 05-2019
Publisher: EDP Sciences
Date: 11-2018
DOI: 10.1051/0004-6361/201833533
Abstract: Observations have shown that massive star-forming clumps are present in the internal structure of high-redshift galaxies. One way to study these clumps in detail with a higher spatial resolution is by exploiting the power of strong gravitational lensing which stretches images on the sky. In this work, we present an analysis of the clumpy galaxy A68-HLS115 at z = 1.5858, located behind the cluster Abell 68, but strongly lensed by a cluster galaxy member. Resolved observations with SINFONI/VLT in the near-infrared (NIR) show H α , H β , [NII], and [OIII] emission lines. Combined with images covering the B band to the far-infrared (FIR) and CO(2–1) observations, this makes this galaxy one of the only sources for which such multi-band observations are available and for which it is possible to study the properties of resolved star-forming clumps and to perform a detailed analysis of the integrated properties, kinematics, and metallicity. We obtain a stability of υ rot / σ 0 = 2.73 by modeling the kinematics, which means that the galaxy is dominated by rotation, but this ratio also indicates that the disk is marginally stable. We find a high intrinsic velocity dispersion of 80 ± 10 km s −1 that could be explained by the high gas fraction of f gas = 0.75 ± 0.15 observed in this galaxy. This high f gas and the observed sSFR of 3.12 Gyr −1 suggest that the disk turbulence and instabilities are mostly regulated by incoming gas (available gas reservoir for star formation). The direct measure of the Toomre stability criterion of Q crit = 0.70 could also indicate the presence of a quasi-stable thick disk. Finally, we identify three clumps in the H α map which have similar velocity dispersions, metallicities, and seem to be embedded in the rotating disk. These three clumps contribute together to ∼40% on the SFR H α of the galaxy and show a star formation rate density about ∼100 times higher than HII regions in the local Universe.
Publisher: EDP Sciences
Date: 05-2019
DOI: 10.1051/0004-6361/201935356
Abstract: Context. Since 1998, a planet-search around main sequence stars within 50 pc in the southern hemisphere has been underway with the CORALIE spectrograph at La Silla Observatory. Aims. With an observing time span of more than 20 yr, the CORALIE survey is able to detect long-term trends in data with masses and separations large enough to select ideal targets for direct imaging. Detecting these giant companion candidates will allow us to start bridging the gap between radial-velocity-detected exoplanets and directly imaged planets and brown dwarfs. Methods. Long-term precise Doppler measurements with the CORALIE spectrograph reveal radial-velocity signatures of massive planetary companions and brown dwarfs on long-period orbits. Results. In this paper, we report the discovery of new companions orbiting HD 181234, HD 13724, HD 25015, HD 92987 and HD 50499. We also report updated orbital parameters for HD 50499b, HD 92788b and HD 98649b. In addition, we confirm the recent detection of HD 92788c. The newly reported companions span a period range of 15.6–40.4 yr and a mass domain of 2.93–26.77 M Jup , the latter of which straddles the nominal boundary between planets and brown dwarfs. Conclusions. We report the detection of five new companions and updated parameters of four known extrasolar planets. We identify at least some of these companions to be promising candidates for imaging and further characterisation.
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: 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: EDP Sciences
Date: 28-10-2019
DOI: 10.1051/0004-6361/201935896
Abstract: We compare the molecular and ionized gas kinematics of two strongly lensed galaxies at z ∼ 1 that lie on the main sequence at this redshift. The observations were made with ALMA and MUSE, respectively. We derive the CO and [O II ] rotation curves and dispersion profiles of these two galaxies. We find a difference between the observed molecular and ionized gas rotation curves for one of the two galaxies, the Cosmic Snake, for which we obtain a spatial resolution of a few hundred parsec along the major axis. The rotation curve of the molecular gas is steeper than the rotation curve of the ionized gas. In the second galaxy, A521, the molecular and ionized gas rotation curves are consistent, but the spatial resolution is only a few kiloparsec on the major axis. Using simulations, we investigate the effect of the thickness of the gas disk and effective radius on the observed rotation curves and find that a more extended and thicker disk smoothens the curve. We also find that the presence of a strongly inclined ( 70°) thick disk ( 1 kpc) can smoothen the rotation curve because it degrades the spatial resolution along the line of sight. By building a model using a stellar disk and two gas disks, we reproduce the rotation curves of the Cosmic Snake with a molecular gas disk that is more massive and more radially and vertically concentrated than the ionized gas disk. Finally, we also obtain an intrinsic velocity dispersion in the Cosmic Snake of 18.5 ± 7 km s −1 and 19.5 ± 6 km s −1 for the molecular and ionized gas, respectively, which is consistent with a molecular disk with a smaller and thinner disk. For A521, the intrinsic velocity dispersion values are 11 ± 8 km s −1 and 54 ± 11 km s −1 , with a higher value for the ionized gas. This could indicate that the ionized gas disk is thicker and more turbulent in this galaxy. These results highlight the ersity of the kinematics of galaxies at z ∼ 1 and the different spatial distribution of the molecular and ionized gas disks. It suggests the presence of thick ionized gas disks at this epoch and that the formation of the molecular gas is limited to the midplane and center of the galaxy in some objects.
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: 21-12-2017
Start Date: 2016
End Date: 2019
Funder: Fonds de Recherche du Québec – Nature et technologies
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