ABSTRACT
We measure the properties of optical emission lines in multiple locations across the Large Magellanic Cloud (LMC) using the Australian National University 2.3-m telescope and the Wide-Field ...Spectrograph (WiFeS). From these measurements, we interpolate maps of the gas-phase metallicity, extinction, Hα radial velocity, and Hα velocity dispersion across the LMC. The LMC metallicity maps show a complex structure that cannot be explained by a simple radial gradient. The bright H ii region 30 Doradus stands out as a region of high extinction. The Hα and H i gas radial velocities are mostly consistent except for a region to the south and east of the LMC centre. The Hα velocity dispersion is almost always higher than the H i velocity dispersion, except in the region that shows the divergence in radial velocity, where the H i velocity dispersion is greater than the Hα velocity dispersion. This suggests that the H i gas is diverging from the stellar radial velocity, perhaps as a result of inflow or outflow of H i gas. The study of dwarf galaxies like the LMC is important as they are the building blocks of larger galaxies like our own Milky Way. The maps provided in this work show details not accessible in the study of more distant dwarf galaxies.
We present JADES JWST/NIRSpec spectroscopy of GN-z11, the most luminous candidate
z
> 10 Lyman break galaxy in the GOODS-North field with
M
UV
= −21.5. We derive a redshift of
z
= 10.603 (lower ...than previous determinations) based on multiple emission lines in our low and medium resolution spectra over 0.7 − 5.3 μm. We significantly detect the continuum and measure a blue rest-UV spectral slope of
β
= −2.4. Remarkably, we see spatially extended Lyman-
α
in emission (despite the highly neutral intergalactic medium expected at this early epoch), offset 555 km s
−1
redwards of the systemic redshift. From our measurements of collisionally excited lines of both low and high ionisation (including O
II
λ
3727, Ne
III
λ
3869, and C
III
λ
1909), we infer a high ionisation parameter (log
U
∼ −2). We detect the rarely seen N
IV
λ
1486 and N
III
λ
1748 lines in both our low and medium resolution spectra, with other high ionisation lines seen in the low resolution spectrum, such as He
II
(blended with O
III
) and C
IV
(with a possible P-Cygni profile). Based on the observed rest-UV line ratios, we cannot conclusively rule out photoionisation from an active galactic nucleus (AGN), although the high C
III
/He
II
and N
III
/He
II
ratios are compatible with a star formation explanation. If the observed emission lines are powered by star formation, then the strong N
III
λ
1748 observed may imply an unusually high
N
/
O
abundance. Balmer emission lines (H
γ
, H
δ
) are also detected, and if powered by star formation rather than an AGN, we infer a star formation rate of ∼20 − 30
M
⊙
yr
−1
(depending on the initial mass function) and low dust attenuation. Our NIRSpec spectroscopy confirms that GN-z11 is a remarkable galaxy with extreme properties seen 430 Myr after the Big Bang.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
Massive, starbursting galaxies in the early Universe represent some of the most extreme objects in the study of galaxy evolution. One such source is HFLS3 ($z which was originally identified as an ...extreme starburst galaxy with mild gravitational magnification ($ Here, we present new observations of HFLS3 with the JWST/NIRSpec integral field unit in both low (PRISM/CLEAR; $R and high spectral resolution (G395H/290LP; $R with high spatial resolution ($ and sensitivity. Using a combination of the NIRSpec data and a new lensing model with accurate spectroscopic redshifts, we find that the $3'' field is crowded, with a lensed arc (C, $z=6.3425 two galaxies to the south (S1 and S2, $z=6.3592 two galaxies to the west (W1, $z=6.3550 W2, $z=6.3628 and two low-redshift interlopers (G1, $z=3.4806 G2, $z=2.00 We present spectral fits and morpho-kinematic maps for each bright emission line (e.g. and from the R2700 data for all sources except G2 (whose spectral lines fall outside the observed wavelengths of the R2700 data). From a line ratio analysis, we find that the galaxies in component C are likely powered by star formation, though we cannot rule out or confirm the presence of active galactic nuclei in the other high-redshift sources. We performed gravitational lens modelling, finding evidence for a two-source composition of the lensed central object and a magnification factor ($ comparable to findings of previous work. The projected distances and velocity offsets of each galaxy suggest that they will merge within the next $ Finally, we examined the dust extinction-corrected H alpha $ of each $z>6$ source, finding that the total star formation ($510 odot $, magnification-corrected) is distributed across the six $z objects over a region of diameter $ Altogether, this suggests that HFLS3 is not a single starburst galaxy, but instead a merging system of star-forming galaxies in the epoch of reionisation.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
ABSTRACT
We have entered a new era where integral-field spectroscopic surveys of galaxies are sufficiently large to adequately sample large-scale structure over a cosmologically significant volume. ...This was the primary design goal of the SAMI Galaxy Survey. Here, in Data Release 3, we release data for the full sample of 3068 unique galaxies observed. This includes the SAMI cluster sample of 888 unique galaxies for the first time. For each galaxy, there are two primary spectral cubes covering the blue (370–570 nm) and red (630–740 nm) optical wavelength ranges at spectral resolving power of R = 1808 and 4304, respectively. For each primary cube, we also provide three spatially binned spectral cubes and a set of standardized aperture spectra. For each galaxy, we include complete 2D maps from parametrized fitting to the emission-line and absorption-line spectral data. These maps provide information on the gas ionization and kinematics, stellar kinematics and populations, and more. All data are available online through Australian Astronomical Optics Data Central.
We present emission-line ratios from a sample of 27 Lyman-break galaxies from
z
∼ 5.5 − 9.5 with −17.0 <
M
1500
< −20.4, measured from ultra-deep JWST/NIRSpec multi-object spectroscopy from the ...JWST Advanced Deep Extragalactic Survey (JADES). We used a combination of 28 h deep PRISM/CLEAR and 7 h deep
G
395
M
/
F
290
LP
observations to measure, or place strong constraints on, ratios of widely studied rest-frame optical emission lines including H
α
, H
β
, O
II
λλ
3726, 3729, Ne
III
λ
3869, O
III
λ
4959, O
III
λ
5007, O
I
λ
6300, N
II
λ
6583, and S
II
λλ
6716, 6731 in individual
z
> 5.5 spectra. We find that the emission-line ratios exhibited by these
z
∼ 5.5 − 9.5 galaxies occupy clearly distinct regions of line-ratio space compared to typical
z
∼ 0 − 3 galaxies, instead being more consistent with extreme populations of lower-redshift galaxies. This is best illustrated by the O
III
/O
II
ratio, tracing interstellar medium (ISM) ionisation, in which we observe more than half of our sample to have O
III
/O
II
> 10. Our high signal-to-noise spectra reveal more than an order of magnitude of scatter in line ratios such as O
II
/H
β
and O
III
/O
II
, indicating significant diversity in the ISM conditions within the sample. We find no convincing detections of N
II
λ
6583 in our sample, either in individual galaxies, or a stack of all
G
395
M
/
F
290
LP
spectra. The emission-line ratios observed in our sample are generally consistent with galaxies with extremely high ionisation parameters (log
U
∼ −1.5), and a range of metallicities spanning from ∼0.1 ×
Z
⊙
to higher than ∼0.3 ×
Z
⊙
, suggesting we are probing low-metallicity systems undergoing periods of rapid star formation, driving strong radiation fields. These results highlight the value of deep observations in constraining the properties of individual galaxies, and hence probing diversity within galaxy population.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
ABSTRACT
We present an interstellar medium and stellar population analysis of three spectroscopically confirmed z > 7 galaxies in the Early Release Observations JWST/NIRCam and JWST/NIRSpec data of ...the SMACS J0723.3−7327 cluster.
We use the Bayesian spectral energy distribution-fitting code prospector with a flexible star formation history (SFH), a variable dust attenuation law, and a self-consistent model of nebular emission (continuum and emission lines). Importantly, we self-consistently fit both the emission line fluxes from JWST/NIRSpec and the broad-band photometry from JWST/NIRCam, taking into account slit-loss effects. We find that these three z=7.6–8.5 galaxies (M⋆ ≈ 108 M⊙) are young with rising SFHs and mass-weighted ages of 3–4 Myr, though we find indications for underlying older stellar populations. The inferred gas-phase metallicities broadly agree with the direct metallicity estimates from the auroral lines. The galaxy with the lowest gas-phase metallicity (Zgas= 0.06 Z⊙) has a steeply rising SFH, is very compact (<0.2 kpc), and has a high star formation rate surface density (ΣSFR ≈ 22 M⊙ yr−1 kpc−2), consistent with rapid gas accretion. The two other objects with higher gas-phase metallicities show more complex multicomponent morphologies on kpc scales, indicating that their recent increase in star formation rate is driven by mergers or internal, gravitational instabilities. We discuss effects of assuming different SFH priors or only fitting the photometric data. Our analysis highlights the strength and importance of combining JWST imaging and spectroscopy for fully assessing the nature of galaxies at the earliest epochs.
ABSTRACT Recent cosmological hydrodynamical simulations suggest that integral field spectroscopy can connect the high-order stellar kinematic moments h3 (∼skewness) and h4 (∼kurtosis) in galaxies to ...their cosmological assembly history. Here, we assess these results by measuring the stellar kinematics on a sample of 315 galaxies, without a morphological selection, using two-dimensional integral field data from the SAMI Galaxy Survey. Proxies for the spin parameter ( ) and ellipticity ( ) are used to separate fast and slow rotators; there exists a good correspondence to regular and non-regular rotators, respectively, as also seen in earlier studies. We confirm that regular rotators show a strong h3 versus anti-correlation, whereas quasi-regular and non-regular rotators show a more vertical relation in h3 and . Motivated by recent cosmological simulations, we develop an alternative approach to kinematically classify galaxies from their individual h3 versus signatures. Within the SAMI Galaxy Survey, we identify five classes of high-order stellar kinematic signatures using Gaussian mixture models. Class 1 corresponds to slow rotators, whereas Classes 2-5 correspond to fast rotators. We find that galaxies with similar values can show distinctly different signatures. Class 5 objects are previously unidentified fast rotators that show a weak h3 versus anti-correlation. From simulations, these objects are predicted to be disk-less galaxies formed by gas-poor mergers. From morphological examination, however, there is evidence for large stellar disks. Instead, Class 5 objects are more likely disturbed galaxies, have counter-rotating bulges, or bars in edge-on galaxies. Finally, we interpret the strong anti-correlation in h3 versus as evidence for disks in most fast rotators, suggesting a dearth of gas-poor mergers among fast rotators.
PDF
