Abstract
We investigate galactic winds in the HizEA galaxies, a collection of 46 late-stage galaxy mergers at
z
= 0.4–0.8, with stellar masses of
log
(
M
*
/
M
⊙
)
=
10.4
–
11.5
, star formation ...rates (SFRs) of 20–500
M
⊙
yr
−1
, and ultra-compact (a few 100 pc) central star-forming regions. We measure their gas kinematics using the Mg
ii
λ
λ
2796,2803 absorption lines in optical spectra from MMT, Magellan, and Keck. We find evidence of outflows in 90% of targets, with maximum outflow velocities of 550–3200 km s
−1
. We combine these data with ten samples from the literature to construct scaling relations for outflow velocity versus SFR, star formation surface density (Σ
SFR
),
M
*
, and SFR/
M
*
. The HizEA galaxies extend the dynamic range of the scaling relations by a factor of ∼2–4 in outflow velocity and an order of magnitude in SFR and Σ
SFR
. The ensemble scaling relations exhibit strong correlations between outflow velocity, SFR, SFR/
R
, and Σ
SFR
, and weaker correlations with
M
*
and SFR/
M
*
. The HizEA galaxies are mild outliers on the SFR and
M
*
scaling relations, but they connect smoothly with more typical star-forming galaxies on plots of outflow velocity versus SFR/
R
and Σ
SFR
. These results provide further evidence that the HizEA galaxies’ exceptional outflow velocities are a consequence of their extreme star formation conditions rather than hidden black hole activity, and they strengthen previous claims that Σ
SFR
is one of the most important properties governing the velocities of galactic winds.
Abstract
We present results on the properties of extreme gas outflows in massive (
M
*
∼ 10
11
M
⊙
), compact, starburst (star formation rate, SFR∼ 200
M
⊙
yr
−1
) galaxies at
z
= 0.4–0.7 with very ...high star formation surface densities (Σ
SFR
∼ 2000
M
⊙
yr
−1
kpc
−2
). Using optical Keck/HIRES spectroscopy of 14 HizEA starburst galaxies, we identify outflows with maximum velocities of 820–2860 km s
−1
. High-resolution spectroscopy allows us to measure precise column densities and covering fractions as a function of outflow velocity and characterize the kinematics and structure of the cool gas outflow phase (
T
∼ 10
4
K). We find substantial variation in the absorption profiles, which likely reflects the complex morphology of inhomogeneously distributed, clumpy gas and the intricacy of the turbulent mixing layers between the cold and hot outflow phases. There is not a straightforward correlation between the bursts in the galaxies’ star formation histories and their wind absorption line profiles, as might naively be expected for starburst-driven winds. The lack of strong Mg
ii
absorption at the systemic velocity is likely an orientation effect, where the observations are down the axis of a blowout. We infer high mass outflow rates of ∼50–2200
M
⊙
yr
−1
, assuming a fiducial outflow size of 5 kpc, and mass loading factors of
η
∼ 5 for most of the sample. While these values have high uncertainties, they suggest that starburst galaxies are capable of ejecting very large amounts of cool gas that will substantially impact their future evolution.
A 3D View of Orion. I. Barnard's Loop Foley, Michael M.; Goodman, Alyssa; Zucker, Catherine ...
Astrophysical journal/The Astrophysical journal,
04/2023, Letnik:
947, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
Barnard’s Loop is a famous arc of H
α
emission located in the Orion star-forming region. Here, we provide evidence of a possible formation mechanism for Barnard’s Loop and compare our ...results with recent work suggesting a major feedback event occurred in the region around 6 Myr ago. We present a 3D model of the large-scale Orion region, indicating coherent, radial, 3D expansion of the OBP-Near/Briceño-1 (OBP-B1) cluster in the middle of a large dust cavity. The large-scale gas in the region also appears to be expanding from a central point, originally proposed to be Orion X. OBP-B1 appears to serve as another possible center, and we evaluate whether Orion X or OBP-B1 is more likely to have caused the expansion. We find that neither cluster served as the single expansion center, but rather a combination of feedback from both likely propelled the expansion. Recent 3D dust maps are used to characterize the 3D topology of the entire region, which shows Barnard’s Loop’s correspondence with a large dust cavity around the OPB-B1 cluster. The molecular clouds Orion A, Orion B, and Orion
λ
reside on the shell of this cavity. Simple estimates of gravitational effects from both stars and gas indicate that the expansion of this asymmetric cavity likely induced anisotropy in the kinematics of OBP-B1. We conclude that feedback from OBP-B1 has affected the structure of the Orion A, Orion B, and Orion
λ
molecular clouds and may have played a major role in the formation of Barnard’s Loop.
Abstract
We present results on the nature of extreme ejective feedback episodes and the physical conditions of a population of massive (
M
*
∼ 10
11
M
⊙
), compact starburst galaxies at
z
= 0.4–0.7. ...We use data from Keck/NIRSPEC, SDSS, Gemini/GMOS, MMT, and Magellan/MagE to measure rest-frame optical and near-IR spectra of 14 starburst galaxies with extremely high star formation rate surface densities (mean Σ
SFR
∼ 2000
M
⊙
yr
−1
kpc
−2
) and powerful galactic outflows (maximum speeds
v
98
∼ 1000–3000 km s
−1
). Our unique data set includes an ensemble of both emission (O
ii
λλ
3726,3729, H
β
, O
iii
λλ
4959,5007, H
α
, N
ii
λλ
6549,6585, and S
ii
λλ
6716,6731) and absorption (Mg
ii
λλ
2796,2803, and Fe
ii
λ
2586) lines that allow us to investigate the kinematics of the cool gas phase (
T
∼ 10
4
K) in the outflows. Employing a suite of line ratio diagnostic diagrams, we find that the central starbursts are characterized by high electron densities (median
n
e
∼ 530 cm
−3
), and high metallicity (solar or supersolar). We show that the outflows are most likely driven by stellar feedback emerging from the extreme central starburst, rather than by an AGN. We also present multiple intriguing observational signatures suggesting that these galaxies may have substantial Lyman continuum (LyC) photon leakage, including weak S
ii
nebular emission lines. Our results imply that these galaxies may be captured in a short-lived phase of extreme star formation and feedback where much of their gas is violently blown out by powerful outflows that open up channels for LyC photons to escape.
Abstract
We present a phase-space study of two stellar groups located at the core of the Orion Complex: Briceño-1 and Orion Belt Population-near (OBP-near). We identify the groups with the ...unsupervised clustering algorithm, Shared Nearest Neighbor (SNN), which previously identified 12 new stellar substructures in the Orion Complex. For each of the two groups, we derive the 3D space motions of individual stars using Gaia EDR3 proper motions supplemented by radial velocities from Gaia DR2, APOGEE-2, and GALAH DR3. We present evidence for radial expansion of the two groups from a common center. Unlike previous work, our study suggests that evidence of stellar group expansion is confined only to OBP-near and Briceño-1, whereas the rest of the groups in the complex show more complicated motions. Interestingly, the stars in the two groups lie at the center of a dust shell, as revealed via an extant 3D dust map. The exact mechanism that produces such coherent motions remains unclear, while the observed radial expansion and dust shell suggest that massive stellar feedback could have influenced the star formation history of these groups.
We reconstructed the star formation history of the Sco-Cen OB association using a novel high-resolution age map of the region. We developed an approach to produce robust ages for Sco-Cen’s recently ...identified 37 stellar clusters using the
SigMA
algorithm. The Sco-Cen star formation timeline reveals four periods of enhanced star formation activity, or bursts, remarkably separated by about 5 Myr. Of these, the second burst, which occurred about 15 million years ago, is by far the dominant one, and most of Sco-Cen’s stars and clusters were in place by the end of this burst. The formation of stars and clusters in Sco-Cen is correlated but not linearly, implying that more stars were formed per cluster during the peak of the star formation rate. Most of the clusters that are large enough to have supernova precursors were formed during the second burst around 15 Myr ago. Star and cluster formation activity has been continuously declining since then. We have clear evidence that Sco-Cen formed from the inside out and that it contains 100-pc long chains of contiguous clusters exhibiting well-defined age gradients, from massive older clusters to smaller young clusters. These observables suggest an important role for feedback in forming about half of Sco-Cen stars, although follow-up work is needed to quantify this statement. Finally, we confirm that the Upper-Sco age controversy discussed in the literature during the last decades is solved: the nine clusters previously lumped together as Upper-Sco, a benchmark region for planet formation studies, exhibit a wide range of ages from 3 to 19 Myr.
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