CLASSY III. The Properties of Starburst-driven Warm Ionized Outflows*

Xu, Xinfeng; Heckman, Timothy M.; Henry, Alaina; Berg, Danielle A.; Chisholm, John; James, Bethan L.; Martin, Crystal L.; Stark, Daniel P.; Aloisi, Alessandra; Amorín, R.; Arellano-Córdova, K. Z.; Bordoloi, Rongmon; Charlot, S.; Chen, Zuyi; Hayes, Matthew; Mingozzi, Matilde; Sugahara, Yuma; Kewley, Lisa J.; Ouchi, Masami; Scarlata, Claudia; Steidel, C. C.

doi:10.3847/1538-4357/ac6d56

Cited by 37 publications

(101 citation statements)

References 101 publications

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“…The mass loading factors of 𝜂 ≈ 1 − 3 and an escaping wind are quite comparable to those found using UV absorption (Xu et al 2022), and via emission lines such as H𝛼 (McQuinn et al 2019). In the more comparable methodology of Xu et al, the mass flow rate is calculated assuming 𝑟 wind scales with optical size of the starburst.…”

Section: Implications and Comparisonssupporting

confidence: 72%

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Accelerating galaxy winds during the big bang of starbursts

Hayes

2022

Monthly Notices of the Royal Astronomical Society: Letters

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We develop a new method to infer the temporal, geometric, and energetic properties of galaxy outflows, by combining stellar spectral modeling to infer starburst ages, and absorption lines to measure velocities. If winds are accelerated with time during a starburst event, then these two measurements enable us to solve for the wind radius, similarly to length scales and the Hubble parameter in Big Bang cosmology. This wind radius is the vital, but hard-to-constrain parameter in wind physics. We demonstrate the method using spectra of 87 starburst galaxies at z = 0.05 − 0.44, finding that winds accelerate throughout the starburst phase and grow to typical radii of ≈1 kpc in ≈10 Myr. Mass flow rates increase rapidly with time, and the mass-loading factor exceeds unity at about 10 Myr – while still being accelerated, the gas will likely unbind from the local potential and enrich the circumgalactic medium. We model the mechanical energy available from stellar winds and supernovae, and estimate that a negligible amount is accounted for in the cool outflow at early times. However, the energy deposition increases rapidly and ∼10% of the budget is accounted for in the cool flow at 10 Myr, similar to some recent hydrodynamical simulations. We discuss how this model can be developed, especially for high-redshift galaxies.

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Section: Implications and Comparisonssupporting

confidence: 72%

“…outflow velocities, massloading factors; 𝜂 ≡ 𝑀 out /SFR) with physical galaxy properties of SFR and stellar mass (e.g. Heckman et al 2015;Chisholm et al 2017;Xu et al 2022).…”

Section: Introductionmentioning

confidence: 99%

Accelerating galaxy winds during the big bang of starbursts

Hayes

2022

Monthly Notices of the Royal Astronomical Society: Letters

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“…of the low-ionization gas. Absorption-line fits are presented in CLASSY III (Xu et al 2022). Such detailed absorption-line analysis can then be used to analyze covering fractions, ion column densities, and outflow rates.…”

Section: The Physical Properties Of Outflowsmentioning

confidence: 99%

The COS Legacy Archive Spectroscopy Survey (CLASSY) Treasury Atlas*

Berg¹,

James²,

King³

et al. 2022

ApJS

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Far-ultraviolet (FUV; ∼1200–2000 Å) spectra are fundamental to our understanding of star-forming galaxies, providing a unique window on massive stellar populations, chemical evolution, feedback processes, and reionization. The launch of the James Webb Space Telescope will soon usher in a new era, pushing the UV spectroscopic frontier to higher redshifts than ever before; however, its success hinges on a comprehensive understanding of the massive star populations and gas conditions that power the observed UV spectral features. This requires a level of detail that is only possible with a combination of ample wavelength coverage, signal-to-noise, spectral-resolution, and sample diversity that has not yet been achieved by any FUV spectral database. We present the Cosmic Origins Spectrograph Legacy Spectroscopic Survey (CLASSY) treasury and its first high-level science product, the CLASSY atlas. CLASSY builds on the Hubble Space Telescope (HST) archive to construct the first high-quality (S/N1500 Å ≳ 5/resel), high-resolution (R ∼ 15,000) FUV spectral database of 45 nearby (0.002 < z < 0.182) star-forming galaxies. The CLASSY atlas, available to the public via the CLASSY website, is the result of optimally extracting and coadding 170 archival+new spectra from 312 orbits of HST observations. The CLASSY sample covers a broad range of properties including stellar mass (6.2 < log M ⋆(M ⊙) < 10.1), star formation rate (−2.0 < log SFR (M ⊙ yr−1) < +1.6), direct gas-phase metallicity (7.0 < 12+log(O/H) < 8.8), ionization (0.5 < O32 < 38.0), reddening (0.02 < E(B − V) < 0.67), and nebular density (10 < n e (cm−3) < 1120). CLASSY is biased to UV-bright star-forming galaxies, resulting in a sample that is consistent with the z ∼ 0 mass–metallicity relationship, but is offset to higher star formation rates by roughly 2 dex, similar to z ≳ 2 galaxies. This unique set of properties makes the CLASSY atlas the benchmark training set for star-forming galaxies across cosmic time.

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“…Targets whose spatial or spectral profile had GFWHM < 0 6, with single-peaked profiles, are classified as the CLASSY "compact sources." This classification scheme was further verified by inspecting the half-light radii (r 50 ) measured from the COS acquisition images (Xu et al 2022). All galaxies that were classified as "compact" have r 50 < 0 3, "extended" sources have r 50 > 0 6, and "MC" sources typically have 0 3 < r 50 < 0 6.…”

Section: Data Reductionmentioning

confidence: 89%

“…In both cases we convolve the chosen LSF with a Gaussian profile with a width equal to that measured from the COS acquisition images, thus creating a non-pointsource LSF. Lines were fit using a Gaussian line profile (as detailed in Xu et al 2022) on stellar-continuum-subtracted data (as detailed in J. Chisholm et al and P. Senchyna et al, both in preparation), binned by 15 pixels, using non-point-source LSFs binned by the same amount.…”

Section: Absorption-line Fittingmentioning

confidence: 99%

CLASSY. II. A Technical Overview of the COS Legacy Archive Spectroscopic Survey*

James

Berg

King

et al. 2022

ApJS

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The COS Legacy Archive Spectroscopic SurveY (CLASSY) is designed to provide the community with a spectral atlas of 45 nearby star-forming galaxies that were chosen to cover similar properties to those seen at high z (z > 6). The prime high-level science product of CLASSY is accurately coadded UV spectra, ranging from ∼1000 to 2000 Å, derived from a combination of archival and new data obtained with HST’s Cosmic Origins Spectrograph (COS). This paper details the multistage technical processes of creating this prime data product and the methodologies involved in extracting, reducing, aligning, and coadding far-ultraviolet and near-ultraviolet (NUV) spectra. We provide guidelines on how to successfully utilize COS observations of extended sources, despite COS being optimized for point sources, and best-practice recommendations for the coaddition of UV spectra in general. Moreover, we discuss the effects of our reduction and coaddition techniques in the scientific application of the CLASSY data. In particular, we find that accurately accounting for flux calibration offsets can affect the derived properties of the stellar populations, while customized extractions of NUV spectra for extended sources are essential for correctly diagnosing the metallicity of galaxies via C iii] nebular emission. Despite changes in spectral resolution of up to ∼25% between individual data sets (due to changes in the COS line-spread function), no adverse affects were observed on the difference in velocity width and outflow velocities of isolated absorption lines when measured in the final combined data products, owing in part to our signal-to-noise regime of S/N < 20.

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CLASSY III. The Properties of Starburst-driven Warm Ionized Outflows*

Cited by 37 publications

References 101 publications

Accelerating galaxy winds during the big bang of starbursts

Accelerating galaxy winds during the big bang of starbursts

The COS Legacy Archive Spectroscopy Survey (CLASSY) Treasury Atlas*

CLASSY. II. A Technical Overview of the COS Legacy Archive Spectroscopic Survey*

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