We report the lens mass and distance measurements of the nearby microlensing event TCP J05074264+2447555 (Kojima-1). We measure the microlens parallax vector using Spitzer and ground-based light ...curves with constraints on the direction of lens-source relative proper motion derived from Very Large Telescope Interferometer (VLTI) GRAVITY observations. Combining this determination with the angular Einstein radius measured by VLTI-GRAVITY observations, we find that the lens is a star with mass at a distance DL = 429 21 pc. We find that the blended light basically all comes from the lens. The lens-source proper motion is , so with currently available adaptive-optics instruments, the lens and source can be resolved in 2021. This is the first microlensing event whose lens mass is unambiguously measured by interferometry + satellite-parallax observations, which opens a new window for mass measurements of isolated objects such as stellar-mass black holes.
Abstract
Direct observations of low-mass, low-metallicity galaxies at
z
≳ 4 provide an indispensable opportunity for detailed inspection of the ionization radiation, gas flow, and metal enrichment in ...sources similar to those that reionized the universe. Combining the James Webb Space Telescope (JWST), Very Large Telescope/MUSE, and Atacama Large Millimeter/submillimeter Array, we present detailed observations of a strongly lensed, low-mass (≈10
7.6
M
⊙
) galaxy at
z
= 3.98 (also see Vanzella et al.). We identify strong narrow nebular emission, including C
iv
λ
λ
1548, 1550, He
ii
λ
1640, O
iii
λ
λ
1661, 1666, Ne
iii
λ
3868, O
ii
λ
3727, and the Balmer series of hydrogen from this galaxy, indicating a metal-poor H
ii
region (≲0.12
Z
⊙
) powered by massive stars. Further, we detect a metal-enriched damped Ly
α
system (DLA) associated with the galaxy with the H
i
column density of
N
H I
≈ 10
21.8
cm
−2
. The metallicity of the associated DLA may reach the supersolar metallicity (≳
Z
⊙
). Moreover, thanks to JWST and gravitational lensing, we present the resolved UV slope (
β
) map at the spatial resolution of ≈100 pc at
z
= 4, with steep UV slopes reaching
β
≈ −2.5 around three star-forming clumps. Combining with low-redshift analogs, our observations suggest that low-mass, low-metallicity galaxies, which dominate reionization, could be surrounded by a high covering fraction of the metal-enriched, neutral-gaseous clouds. This implies that the metal enrichment of low-mass galaxies is highly efficient, and further supports that in low-mass galaxies, only a small fraction of ionizing radiation can escape through the interstellar or circumgalactic channels with low-column-density neutral gas.
ABSTRACT
We analysed the high-resolution (up to ∼0.2 arcsec) ALMA CO (2–1) and 1.3 mm dust continuum data of eight gas-rich post-starburst galaxies (PSBs) in the local Universe, six of which had been ...studied by a recent work. In contrast to this study reporting the detections of extraordinarily compact (i.e. unresolved) reservoirs of molecular gas in the six PSBs, our visibility-plane analysis resolves the CO (2–1) emission in all eight PSBs with effective radii (Re, CO) of $0.8_{-0.4}^{+0.9}$ kpc, typically consisting of gaseous components at both circumnuclear and extended disc scales. With this new analysis, we find that the CO sizes of gas-rich PSBs are compact with respect to their stellar sizes (median ratio $=0.43_{-0.21}^{+0.27}$), but comparable to the sizes of the gas discs seen in local luminous infrared galaxies (LIRGs) and early-type galaxies. We also find that the CO-to-stellar size ratio of gas-rich PSBs is potentially correlated with the gas depletion time-scale, placing them as transitional objects between LIRGs and early-type galaxies from an evolutionary perspective. Finally, the star formation efficiency of the observed PSBs appear consistent with those of star-forming galaxies on the Kennicutt–Schmidt relation, showing no sign of suppressed star formation from turbulent heating.
Abstract We characterize the multiphase circumgalactic medium (CGM) and galaxy properties at z = 6.0–6.5 in four quasar fields from the James Webb Space Telescope A SPectroscopic survey of biased ...halos In the Reionization Era (ASPIRE) program. We use the Very Large Telescope/X-shooter spectra of quasar J0305–3150 to identify one new metal absorber at z = 6.2713 with multiple transitions (O i , Mg ii , Fe ii, and C ii ). They are combined with the published absorbing systems in Davies et al. at the same redshift range to form a sample of nine metal absorbers at z = 6.03–6.49. We identify eight galaxies within 1000 km s −1 and 350 kpc around the absorbing gas from the ASPIRE spectroscopic data, with their redshifts secured by O iii ( λ λ 4959, 5007) doublets and H β emission lines. Our spectral energy distribution fitting indicates that the absorbing galaxies have stellar masses ranging from 10 7.2 to 10 8.8 M ⊙ and metallicity between 0.02 and 0.4 solar. Notably, the z = 6.2713 system in the J0305–3150 field resides in a galaxy overdensity region, which contains two (tentatively) merging galaxies within 350 kpc and seven galaxies within 1 Mpc. We measure the relative abundances of α elements to iron ( α /Fe) and find that the CGM gas in the most overdense region exhibits a lower α /Fe ratio. Our modeling of the galaxy’s chemical abundance favors a top-heavy stellar initial mass function and hints that we may be witnessing the contribution of the first generation of Population III stars to the CGM at the end of the reionization epoch.
Abstract
The launch of JWST opens a new window for studying the connection between metal-line absorbers and galaxies at the end of the Epoch of Reionization. Previous studies have detected ...absorber–galaxy pairs in limited quantities through ground-based observations. To enhance our understanding of the relationship between absorbers and their host galaxies at
z
> 5, we utilized the NIRCam wide-field slitless spectroscopy to search for absorber-associated galaxies by detecting their rest-frame optical emission lines (e.g., O
III
+ H
β
). We report the discovery of a Mg
ii
-associated galaxy at
z
= 5.428 using data from the JWST ASPIRE program. The Mg
ii
absorber is detected on the spectrum of quasar J0305–3150 with a rest-frame equivalent width of 0.74 Å. The associated galaxy has an O
III
luminosity of 10
42.5
erg s
−1
with an impact parameter of 24.9 pkpc. The joint Hubble Space Telescope–JWST spectral energy distribution (SED) implies a stellar mass and star formation rate of
M
*
≈ 10
8.8
M
⊙
, star-formation rate ≈ 10
M
⊙
yr
−1
. Its O
III
equivalent width and stellar mass are typical of O
III
emitters at this redshift. Furthermore, connecting the outflow starting time to the SED-derived stellar age, the outflow velocity of this galaxy is ∼300 km s
−1
, consistent with theoretical expectations. We identified six additional O
III
emitters with impact parameters of up to ∼300 pkpc at similar redshifts (∣
dv
∣ < 1000 km s
−1
). The observed number is consistent with that in cosmological simulations. This pilot study suggests that systematically investigating the absorber–galaxy connection within the ASPIRE program will provide insights into the metal-enrichment history in the early Universe.
Observations of high-redshift galaxies with unprecedented detail have now been rendered possible with the
James Webb
Space Telescope (JWST). However, accurately quantifying their morphology remains ...uncertain due to potential biases and uncertainties. To address this issue, we used a sample of 1816 nearby DESI galaxies, with a stellar mass range of 10
9.75 − 11.25
M
⊙
, to compute artificial images of galaxies of the same mass located at 0.75 ≤
z
≤ 3 and observed at rest-frame optical wavelength in the Cosmic Evolution Early Release Science (CEERS) survey. We analyzed the effects of cosmological redshift on the measurements of Petrosian radius (
R
p
), half-light radius (
R
50
), asymmetry (
A
), concentration (
C
), axis ratio (
q
), and Sérsic index (
n
). Our results show that
R
p
and
R
50
, calculated using non-parametric methods, are slightly overestimated due to PSF smoothing, while
R
50
,
q
, and
n
obtained through fitting a Sérsic model does not exhibit significant biases. By incorporating a more accurate noise effect removal procedure, we improve the computation of
A
over existing methods, which often overestimate, underestimate, or lead to significant scatter of noise contributions. Due to PSF asymmetry, there is a minor overestimation of
A
for intrinsically symmetric galaxies. However, for intrinsically asymmetric galaxies, PSF smoothing dominates and results in an underestimation of
A
, an effect that becomes more significant with higher intrinsic
A
or at lower resolutions. Moreover, PSF smoothing also leads to an underestimation of
C
, which is notably more pronounced in galaxies with higher intrinsic
C
or at lower resolutions. We developed functions based on resolution level, defined as
R
p
/
FWHM
, for correcting these biases and the associated statistical uncertainties. Applying these corrections, we measured the bias-corrected morphology for the simulated CEERS images and we find that the derived quantities are in good agreement with their intrinsic values – except for
A
, which is robust only for angularly large galaxies where
R
p
/
FWHM
≥ 5. Our correction functions can be applied to other surveys, offering valuable tools for future studies.
Over the past decade, our knowledge of the formation and evolution of massive galaxies has been greatly expanded with the Atacama Large Millimeter/submillimeter Array (ALMA). With unprecedented ...sensitivity and angular resolution, ALMA enables the secure identification of numerous dusty star-forming galaxies (DSFGs) across the bulk of cosmic history, resolving the cold dust and gas components of these galaxies in great detail.Leveraging off the gravitational lensing effects from massive galaxy clusters, I conduct spatially resolved studies of the stellar and dust components of lensed submillimeter galaxies (SMGs) at z ≃ 1-3. I find that although the majority of SMGs host compact dust continuum emission when compared with their stellar components, this is not the case for certain SMGs with relatively low millimeter surface brightness and extended dust profiles. These sources can potentially be interpreted as galaxies undergoing the “inside-out” quenching after the cessation of central starbursts, which is also seen in certain local post-starburst galaxies with extended molecular gas reservoirs.The combination of ALMA observations and gravitational lensing is so powerful that it enables the detection of faint DSFGs that are below the detection limit of traditional blank field surveys. With the ALMA Lensing Cluster Survey and the Herschel Lensing Survey, I obtain accurate dust mass and temperature measurements of 109 lensed DSFGs across z ≃ 0.5-6, whose star-formation rates are much lower than those of conventional SMGs. At given infrared luminosities, I show that the redshift evolution of cold dust temperature remains weak. The high-redshift subset (z ∼ 4) of our sample is dominated by optical/near-IR-dark galaxies that are typically missed in surveys conducted by the Hubble Space Telescope. I conclude that such galaxies are compact in both stellar and dust components, and they could contribute to ∼ 10% of the cosmic star formation rate density and trace the early phase of massive galaxy formation. Such galaxies can also trace overdense galaxy environments and massive dark matter halos, which is demonstrated through the case study of HDF850.1 at z = 5.18, the most luminous SMG in the Hubble Deep Field.Finally, with the long-awaited launch and operation of the James Webb Space Telescope (JWST), the study of massive galaxy formation at high redshifts (z ≳ 6) has been rapidly revolutionized by the unprecedented imaging and spectroscopic capability at infrared wavelengths. I highlight my contribution to the successful commissioning and calibration of the wide-field slitless spectroscopy (WFSS) observing mode of the Near-InfraRed Camera (NIRCam), which enables one of the first direct detections of rest-frame optical emission lines (O III λ5007, Hα) from normal star-forming galaxies in the Epoch of Reionization. I obtain the first direct measurement of O III and Hα luminosity function at z > 6, which confirms the ubiquity of strong emission-line galaxies in the early universe. I demonstrate that the NIRCam WFSS mode is highly ecient in spectroscopically confirming massive star-forming galaxies at high redshifts (z ≃ 5 - 9), and also the large-scale overdense environment that they trace. This sheds light on highly complete spectroscopic surveys of star-forming galaxies, no matter whether dusty or not, towards the Epoch of Reionization, which will further transform our understanding of massive galaxy formation and evolution in the upcoming decade.
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.
Performance of NIRCam on JWST in Flight Rieke, Marcia J.; Kelly, Douglas M.; Misselt, Karl ...
Publications of the Astronomical Society of the Pacific,
02/2023, Letnik:
135, Številka:
1044
Journal Article
Recenzirano
Odprti dostop
Abstract
The Near Infrared Camera for the James Webb Space Telescope (JWST) is delivering the imagery that astronomers have hoped for ever since JWST was proposed back in the 1990s. In the ...Commissioning Period that extended from right after launch to early 2022 July, NIRCam has been subjected to a number of performance tests and operational checks. The camera is exceeding prelaunch expectations in virtually all areas, with very few surprises discovered in flight. NIRCam also delivered the imagery needed by the Wavefront Sensing Team for use in aligning the telescope mirror segments.
Abstract
We study six luminous Ly
α
emitters (LAEs) with very blue rest-frame UV continua at 5.7 ≤
z
≤ 6.6. These LAEs have previous
Hubble Space Telescope
(
HST
) and
Spitzer
IRAC observations. ...Combining our newly acquired
HST
images, we find that their UV-continuum slopes
β
are in a range of −3.4 ≤
β
≤ −2.6. Unlike previous, tentative detections of
β
≃ −3 in photometrically selected, low-luminosity galaxies, our LAEs are spectroscopically confirmed and luminous (
M
UV
< −20 mag). We model their broadband spectral energy distributions (SEDs), and find that two
β
≃ −2.6 ± 0.2 galaxies can be well fitted with young and dust-free stellar populations. However, it becomes increasingly difficult to fit bluer galaxies. We explore further interpretations by including the non-zero LyC escape fraction
f
esc
, very low metallicities, and/or active galactic nucleus contributions. Assuming
f
esc
≃ 0.2, we achieve the bluest slopes
β
≃ −2.7 when nebular emission is considered. This can nearly explain the SEDs of two galaxies with
β
≃ −2.8 and −2.9 (
σ
β
= 0.15). Larger
f
esc
values and very low metallicities are not favored by the strong nebular line emission (evidenced by the IRAC flux) or the observed (IRAC 1 − IRAC 2) color. Finally, we find that the
β
≃ −2.9 galaxy can potentially be well explained by the combination of a very young population with a high
f
esc
(≥0.5) and an old, dusty population. We are not able to produce two
β
≃ −3.4 ± 0.4 galaxies. Future deep spectroscopic observations are needed to fully understand these galaxies.
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