13 research outputs found
Targeted cell imaging properties of a deep red luminescent iridium(III) complex conjugated with a c-Myc signal peptide
A nuclear localisation sequence (NLS) peptide, PAAKRVKLD, derived from the human c-Myc regulator gene, has been functionalised with a long wavelength (λex = 550 nm; λem = 677 nm) cyclometalated organometallic iridium(III) complex to give the conjugate Ir-CMYC. Confocal fluorescence microscopy studies on human fibroblast cells imaged after 18–24 h incubation show that Ir-CMYC concentrations of 80–100 μM promote good cell uptake and nuclear localisation, which was confirmed though co-localisation studies using Hoechst 33342. In comparison, a structurally related, photophysically analogous iridium(III) complex lacking the peptide sequence, Ir-PYR, showed very different biological behaviour, with no evidence of nuclear, lysosomal or autophagic vesicle localisation and significantly increased toxicity to the cells at concentrations >10 μM that induced mitochondrial dysfunction. Supporting UV-visible and circular dichroism spectroscopic studies show that Ir-PYR and Ir-CMYC display similarly low affinities for DNA (ca. 103 M−1), consistent with electrostatic binding. Therefore the translocation and nuclear uptake properties of Ir-CMYC are attributed to the presence of the PAAKRVKLD nuclear localisation sequence in this complex
Rotation Curves in z~1-2 Star-Forming Disks: Evidence for Cored Dark Matter Distributions
We report high-quality, Hα or CO rotation curves (RCs) to several R e for 41 large, massive, star-forming disk galaxies (SFGs) across the peak of cosmic galaxy evolution (z ~ 0.67-2.45), taken with the ESO-VLT, the LBT and IRAM-NOEMA. Most RC41 SFGs have reflection-symmetric RCs plausibly described by equilibrium dynamics. We fit the major axis position-velocity cuts using beam-convolved forward modeling generated in three dimensions, with models that include a bulge and turbulent disk component embedded in a dark matter (DM) halo. We include priors for stellar and molecular gas masses, optical light effective radii and inclinations, and DM masses from abundance-matching scaling relations. Two-thirds or more of the z ≥ 1.2 SFGs are baryon dominated within a few R e of typically 5.5 kpc and have DM fractions less than maximal disks (median ). At lower redshift (z < 1.2), that fraction is less than one-third. DM fractions correlate inversely with the baryonic angular momentum parameter, baryonic surface density, and bulge mass. Inferred low DM fractions cannot apply to the entire disk and halo but more plausibly reflect a flattened, or cored, inner DM density distribution. The typical central "DM deficit" in these cores relative to Navarro-Frenk-White (NFW) distributions is ~30% of the bulge mass. The observations are consistent with rapid radial transport of baryons in the first-generation massive gas-rich halos forming globally gravitationally unstable disks and leading to efficient build-up of massive bulges and central black holes. A combination of heating due to dynamical friction and AGN feedback may drive DM out of the initial cusps.This work was supported in part by DFG/DIP grant
STE/1869 2-1/GE 625/17-
First insights into the ISM at z > 8 with JWST: possible physical implications of a high [O III] λ4363/[O III] λ5007
© 2022 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.We present a detailed analysis of the rest-frame optical emission line ratios for three spectroscopically confirmed galaxies at z > 7.5. The galaxies were identified in the James Webb Space Telescope (JWST) Early Release Observations field SMACS J0723.3 − 7327. By quantitatively comparing Balmer and oxygen line ratios of these galaxies with various low-redshift ‘analogue’ populations (e.g. Green Peas, Blueberries, etc.), we show that no single analogue population captures the diversity of line ratios of all three galaxies observed at z > 7.5. We find that S06355 at z = 7.67 and S10612 at z = 7.66 are similar to local Green Peas and Blueberries. In contrast, S04590 at z = 8.50 appears to be significantly different from the other two galaxies, most resembling extremely low-metallicity systems in the local Universe. Perhaps the most striking spectral feature in S04590 is the curiously high [O III] λ4363/[O III] λ5007 ratio (RO3) of 0.048 (or 0.055 when dust-corrected), implying either extremely high electron temperatures, >3 × 104 K, or gas densities >104 cm−3. Observed line ratios indicate that this galaxy is unlikely to host an AGN. Using photoionization modelling, we show that the inclusion of high-mass X-ray binaries or a high cosmic ray background in addition to a young, low-metallicity stellar population can provide the additional heating necessary to explain the observed high RO3 while remaining consistent with other observed line ratios. Our models represent a first step at accurately characterizing the dominant sources of photoionization and heating at very high redshifts, demonstrating that non-thermal processes may become important as we probe deeper into the Epoch of Reionization.Peer reviewe
Galaxy kinematics and mass estimates at z ∼ 1 from ionised gas and stars
We compare ionised gas and stellar kinematics of 16 star-forming galaxies (log (M⋆/M⊙) = 9.7 − 11.2, SFR =6 − 86M⊙/yr) at z ∼ 1 using near-infrared integral field spectroscopy (IFS) of Hα emission from the KMOS3D survey and optical slit spectroscopy of stellar absorption and gas emission from the LEGA-C survey. Hα is dynamically colder than stars, with higher disc rotation velocities (by ∼45 per cent) and lower disc velocity dispersions (by a factor ∼2). This is similar to trends observed in the local Universe. We find higher rotational support for Hα relative to [OII], potentially explaining systematic offsets in kinematic scaling relations found in the literature. Regarding dynamical mass measurements, for six galaxies with cumulative mass profiles from Jeans Anisotropic Multi-Gaussian Expansion (JAM) models the Hα dynamical mass models agree remarkably well out to ∼10 kpc for all but one galaxy (average ΔΜdyn(Re, F814W) < 0.1 dex). Simpler dynamical mass estimates based on integrated stellar velocity dispersion are less accurate (standard deviation 0.24 dex). Differences in dynamical mass estimates are larger, for example, for galaxies with stronger misalignments of the Hα kinematic major axis and the photometric position angle, highlighting the added value of IFS observations for dynamics studies. The good agreement between the JAM models and the dynamical models based on Hα kinematics at z ∼ 1 corroborates the validity of dynamical mass measurements from Hα IFS observations, which can be more easily obtained for higher redshift galaxies
JADES: Resolving the Stellar Component and Filamentary Overdense Environment of HST-Dark Submillimeter Galaxy HDF850.1 at
HDF850.1 is the brightest submillimeter galaxy (SMG) in the Hubble Deep
Field. It is known as a heavily dust-obscured star-forming galaxy embedded in
an overdense environment at . With nine-band NIRCam images at 0.8-5.0
m obtained through the JWST Advanced Deep Extragalactic Survey (JADES), we
detect and resolve the rest-frame UV-optical counterpart of HDF850.1, which
splits into two components because of heavy dust obscuration in the center. The
southern component leaks UV and H photons, bringing the galaxy
100 times above the empirical relation between infrared excess and UV
continuum slope (IRX-). The northern component is higher in
dust attenuation and thus fainter in UV and H surface brightness. We
construct a spatially resolved dust attenuation map from the NIRCam images,
well matched with the dust continuum emission obtained through millimeter
interferometry. The whole system hosts a stellar mass of
and star-formation rate of
, placing the galaxy at the
massive end of the star-forming main sequence at this epoch. We further confirm
that HDF850.1 resides in a complex overdense environment at ,
which hosts another luminous SMG at (GN10). The filamentary structures
of the overdensity are characterized by 109 H-emitting galaxies
confirmed through NIRCam slitless spectroscopy at 3.9-5 m, of which only
eight were known before the JWST observations. Given the existence of a similar
galaxy overdensity in the GOODS-S field, our results suggest that % of
the cosmic star formation at occur in protocluster environments.Comment: 44 pages, 16 figures, 2 tables. Resubmitted to ApJ after including
the first-round referee's comment
JADES: The emergence and evolution of Ly emission and constraints on the IGM neutral fraction
The rest-frame UV recombination emission line Ly can be powered by
ionising photons from young massive stars in star forming galaxies, but its
ability to be resonantly scattered by neutral gas complicates its
interpretation. For reionization era galaxies, a neutral intergalactic medium
(IGM) will scatter Ly from the line of sight, making Ly a
useful probe of the neutral fraction evolution. Here, we explore Ly in
JWST/NIRSpec spectra from the ongoing JADES programme, which targets hundreds
of galaxies in the well-studied GOODS-S and GOODS-N fields. These sources are
UV-faint (), and thus represent a poorly-explored
class of galaxies. The low spectral resolution () spectra of a subset
of 84 galaxies in GOODS-S with (as derived with optical lines)
are fit with line and continuum models, in order to search for significant line
emission. Through exploration of the R100 data, we find evidence for Ly
in 17 sources. This sample allows us to place observational constraints on the
fraction of galaxies with Ly emission in the redshift range
, with a decrease from to . We also find a positive
correlation between Ly equivalent width and M, as seen in other
samples. These results are used to estimate the neutral gas fraction at
, agreeing with previous results ().Comment: 18 pages, 10 figures. Accepted for publication in A&
Rotating Starburst Cores in Massive Galaxies at z = 2.5
We present spatially resolved ALMA observations of the CO J=3-2 emission line
in two massive galaxies at z=2.5 on the star-forming main sequence. Both
galaxies have compact dusty star-forming cores with effective radii of Re=1.3
kpc and Re=1.2 kpc in the 870 um continuum emission. The spatial extent of
star-forming molecular gas is also compact with Re=1.9 kpc and Re=2.3 kpc, but
more extended than the dust emission. Interpreting the observed
position-velocity diagrams with dynamical models, we find the starburst cores
to be rotation-dominated with the ratio of the maximum rotation velocity to the
local velocity dispersion of v/sigma=7.0 (v=386 km/s) and v/sigma_0=4.1 (v=391
km/s). Given that the descendants of these massive galaxies in the local
universe are likely ellipticals with v/sigma nearly an order of magnitude
lower, the rapidly rotating galaxies would lose significant net angular
momentum in the intervening time. The comparisons among dynamical, stellar,
gas, and dust mass suggest that the starburst CO-to-H2 conversion factor of
alpha_CO=0.8 Msun/(K km/s/pc2) is appropriate in the spatially resolved cores.
The dense cores are likely to be formed in extreme environments similar to the
central regions of local ultraluminous infrared galaxies. Our work also
demonstrates that a combination of medium-resolution CO and high-resolution
dust continuum observations is a powerful tool for characterizing the dynamical
state of molecular gas in distant galaxies.Comment: 6 pages, 4 figures, 1 table, accepted for publication in ApJ Letter
BULGE-FORMING GALAXIES with AN EXTENDED ROTATING DISK at z ∼ 2
We present 0".2-resolution Atacama Large Millimeter/submillimeter Array
observations at 870 um for 25 Halpha-seleced star-forming galaxies (SFGs)
around the main-sequence at z=2.2-2.5. We detect significant 870 um continuum
emission in 16 (64%) of these SFGs. The high-resolution maps reveal that the
dust emission is mostly radiated from a single region close to the galaxy
center. Exploiting the visibility data taken over a wide distance range,
we measure the half-light radii of the rest-frame far-infrared emission for the
best sample of 12 massive galaxies with logM*>11. We find nine galaxies to be
associated with extremely compact dust emission with R_{1/2,870um}<1.5 kpc,
which is more than a factor of 2 smaller than their rest-optical sizes,
R_{1/2,1.6um}=3.2 kpc, and is comparable with optical sizes of massive
quiescent galaxies at similar redshifts. As they have an exponential disk with
Sersic index of n=1.2 in the rest-optical, they are likely to be in the
transition phase from extended disks to compact spheroids. Given their high
star formation rate surface densities within the central 1 kpc of Sigma
SFR1kpc=40 Msol/yr/kpc^2, the intense circumnuclear starbursts can rapidly
build up a central bulge with Sigma M*1kpc>1e10 Msol/kpc^2 in several hundred
Myr, i.e. by z~2. Moreover, ionized gas kinematics reveal that they are
rotation-supported with an angular momentum as large as that of typical SFGs at
z=1-3. Our results suggest bulges are commonly formed in extended rotating
disks by internal processes, not involving major mergers.Comment: 11 pages, 6 figures, 2 tables, accepted for publication in Ap
The evolution of metallicity and metallicity gradients from z = 2.7 to 0.6 with KMOS<sup>3D</sup>
We present measurements of the [NII]/Ha ratio as a probe of gas-phase oxygen
abundance for a sample of 419 star-forming galaxies at z=0.6-2.7 from the
KMOS3D near-IR multi-IFU survey. The mass-metallicity relation (MZR) is
determined consistently with the same sample selection, metallicity tracer, and
methodology over the wide redshift range probed by the survey. We find good
agreement with long-slit surveys in the literature, except for the low-mass
slope of the relation at z~2.3, where this sample is less biased than previous
samples based on optical spectroscopic redshifts. In this regime we measure a
steeper slope than some literature results. Excluding the AGN contribution from
the MZR reduces sensitivity at the high mass end, but produces otherwise
consistent results. There is no significant dependence of the [NII]/Ha ratio on
SFR or environment at fixed redshift and stellar mass. The IFU data allow
spatially resolved measurements of [NII]/Ha, from which we can infer abundance
gradients for 180 galaxies, thus tripling the current sample in the literature.
The observed gradients are on average flat, with only 15 gradients
statistically offset from zero at >3sigma. We have modelled the effect of
beam-smearing, assuming a smooth intrinsic radial gradient and known seeing,
inclination and effective radius for each galaxy. Our seeing-limited
observations can recover up to 70% of the intrinsic gradient for the largest,
face-on disks, but only 30% for the smaller, more inclined galaxies. We do not
find significant trends between observed or corrected gradients and any stellar
population, dynamical or structural galaxy parameters, mostly in agreement with
existing studies with much smaller sample sizes. In cosmological simulations,
strong feedback is generally required to produce flat gradients at high
redshift.Comment: submitted to Ap
Witnessing the Early Growth and Life Cycle of Galaxies with KMOS3D
Near-infrared integral field unit (IFU) spectrographs are powerful tools for investigating galaxy evolution. We report on our recently completed multi-year KMOS3D survey of Halpha, [NII] and [SII] line emission of galaxies at redshift z ~ 0.7 - 2.7 with the K-band Multi-Object Spectrograph (KMOS) at the Very Large Telescope (VLT). With deep observations of 745 targets spanning over two orders of magnitude in galaxy mass, five billion years of cosmic time, and all levels of star formation, KMOS3D provides an unparalleled population-wide census of spatially-resolved kinematics, star formation, outflows and nebular gas conditions. The dataset sheds new light on the physical mechanisms driving the early growth and lifecycle of galaxies, and provides a rich legacy for the astronomical community