DIFFUSE Lyα EMITTING HALOS: A GENERIC PROPERTY OF HIGH-REDSHIFT STAR-FORMING GALAXIES

By C. Steidel, M. Bogosavljević, A. Shapley, Juna A. Kollmeier, Naveen A. Reddy, D. Erb, M. Pettini. 2011

248 citations recorded by the source corpus.

Using a sample of 92 UV continuum-selected, spectroscopically identified galaxies with 〈z〉 = 2.65, all of which have been imaged in the Lyα line with extremely deep narrow-band imaging, we examine galaxy Lyα emission profiles to very faint surface brightness limits. The galaxy sample is representative of spectroscopic samples of Lyman break galaxies (LBGs) at similar redshifts in terms of apparent magnitude, UV luminosity, inferred extinction, and star formation rate and was assembled without regard to Lyα emission properties. Approximately 45% (55%) of the galaxy spectra have Lyα appearing in net absorption (emission), with ≃ 20% satisfying commonly used criteria for the identification of “Lyα emitters” (LAEs; W0(Lyα) ⩾ 20 Å). We use extremely deep stacks of rest-UV continuum and continuum-subtracted Lyα images to show that all sub-samples exhibit diffuse Lyα emission to radii of at least 10″ (∼80 physical kpc). The characteristic exponential scale lengths for Lyα line emission exceed that of the λ0 = 1220 Å UV continuum light by factors of ∼5–10. The surface brightness profiles of Lyα emission are strongly suppressed relative to the UV continuum light in the inner few kpc, by amounts that are tightly correlated with the galaxies’ observed spectral morphology; however, all galaxy sub-subsamples, including that of galaxies for which Lyα appears in net absorption in the spectra, exhibit qualitatively similar diffuse Lyα emission halos. Accounting for the extended Lyα emission halos, which generally would not be detected in the slit spectra of individual objects or with typical narrow-band Lyα imaging, increases the total Lyα flux (and rest equivalent width W0(Lyα)) by an average factor of ∼5, and by a much larger factor for the 80% of LBGs not classified as LAEs. We argue that most, if not all, of the observed Lyα emission in the diffuse halos originates in the galaxy H ii regions but is scattered in our direction by H i gas in the galaxy's circum-galactic medium. The overall intensity of Lyα halos, but not the surface brightness distribution, is strongly correlated with the emission observed in the central ∼1″—more luminous halos are observed for galaxies with stronger central Lyα emission. We show that whether or not a galaxy is classified as a giant “Lyα blob” (LAB) depends sensitively on the Lyα surface brightness threshold reached by an observation. Accounting for diffuse Lyα halos, all LBGs would be LABs if surveys were sensitive to 10 times lower Lyα surface brightness thresholds; similarly, essentially all LBGs would qualify as LAEs.

Subfields: Astronomy and Astrophysics, Computer Vision and Pattern Recognition, Instrumentation

View Paper: https://www.semanticscholar.org/paper/053e0efbb77a4da8c54b4a19c35d3c5258cf330a

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The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. R. Dav'e
2. A. Shapley
3. Naveen A. Reddy
4. P. Hopkins
5. C. Steidel
6. L. Hernquist
7. M. Pettini
8. D. Erb

In Computer Vision and Pattern Recognition

1. R. Bacon
2. Joop Schaye
3. J. Richard
4. Crystal L. Martin
5. D. Erb
6. Y. Harikane
7. C. Steidel
8. A. Shapley

In Instrumentation

1. Naveen A. Reddy
2. A. Shapley
3. C. Steidel
4. D. Erb
5. M. Pettini
6. M. Ouchi
7. P. V. van Dokkum
8. R. Dav'e

Citations in the corpus

• UBIQUITOUS GIANT Lyα NEBULAE AROUND THE BRIGHTEST QUASARS AT z ∼ 3.5 REVEALED WITH MUSE (2016, methodology): “5, these similarities may hint to a common fluorescent origin for quasar fluorescent nebulae and the LBG haloes in the fields observed by Steidel et al. (2011).”
• Extended Lyman-alpha emission from cold accretion streams (2011, methodology): “The black dot-dashed curve is an exponential disk fit to an average of 11 LAB profiles observed at z ≈ 2− 3, reported in Steidel et al. (2011), with no scaling applied.”
• THE GASEOUS ENVIRONMENT OF HIGH-z GALAXIES: PRECISION MEASUREMENTS OF NEUTRAL HYDROGEN IN THE CIRCUMGALACTIC MEDIUM OF z ∼ 2–3 GALAXIES IN THE KECK BARYONIC STRUCTURE SURVEY (2012, background): “…Rauch et al. 1997; Theuns et al. 1998; Davé et al. 1999; Schaye 2001) although there are indications (Barnes et al. 2011) that winds could blow spatially extended halos of gas which may have recently been observed both in absorption (Steidel et al. 2010) and in Lyα emission (Steidel et al. 2011).”
• Extended Lyman α haloes around individual high-redshift galaxies revealed by MUSE (2015, background): “Most notably, the stacking method (Steidel et al. 2011; Matsuda et al. 2012; Feldmeier et al. 2013; Momose et al. 2014) has revealed average properties of Lyα haloes that are broadly consistent with our results for individual sources.”
• Lyman-α spectral properties of five newly discovered Lyman continuum emitters (2016, background): “The Lyα sizes of galaxies are usually bigger than their UV size (Steidel et al. 2011; Hayes et al. 2013).”
• Ionization state of inter-stellar medium in galaxies: evolution, SFR-M * -Z dependence, and ionizing photon escape (2013, background): “Moreover, recent deep narrow-band imaging surveys have indicated diffuse Lyα emitting haloes around high-z star-forming galaxies that are more prominent for LBGs (e.g. Steidel et al. 2011) than LAEs (Feldmeier et al. 2013).”
• Systematic Identification of LAEs for Visible Exploration and Reionization Research Using Subaru HSC (SILVERRUSH). I. Program strategy and clustering properties of ∼2000 Lyα emitters at z = 6–7 over the 0.3–0.5 Gpc2 survey area (2017, background): “Outside the highly-ionized ISM, LAEs show diffuse extended Lyα halos in the circumgalactic medium (CGM) up to a few 10 kpc (Hayashino et al. 2004; Steidel et al. 2011).”
• The realm of the galaxy protoclusters (2016, background): “…due to scattered Lyα photons from central or extended star formation, AGN, and perhaps some amount of gravitational cooling radiation (e.g., Hayashino et al., 2004; Saito et al., 2006; Zheng et al., 2011; Steidel et al., 2011; Dijkstra & Kramer, 2012; Matsuda et al., 2012; Momose et al., 2014; ?”
• Identification of the brightest Lyα emitters at z = 6.6 : Implications for the evolution of the luminosity function in the reionization era (2015, methodology): “Even though Lyα is sometimes observed to be more extended than continuum emission (e.g. Steidel et al. 2011; Momose et al. 2014), we choose to use aperture photometry for all our measurements.”
• The MUSE Hubble Ultra Deep Field Survey - VIII. Extended Lyman-α haloes around high-z star-forming galaxies (2017, background): “Steidel et al. (2011) stacked 92 brighter (RAB ' 24.5) and more massive LBGs at z=2.3−3, finding large Lyα extents of ≈80 physical kpc beyond the mean UV continuum size at a surface brightness level of ∼10−19 erg s−1 cm−2 arcsec−2.”
• Lyα EMISSION FROM GREEN PEAS: THE ROLE OF CIRCUMGALACTIC GAS DENSITY, COVERING, AND KINEMATICS (2015, background): “Spectroscopic line profiles can constrain gas content and kinematics (Erb et al. 2014; Verhamme et al. 2015; Martin et al. 2015), and Lyα imaging can illuminate the gaseous halos around galaxies (Steidel et al. 2011; Zheng et al. 2011; Hayes et al. 2013; Momose et al. 2014).”
• EVIDENCE FOR PopIII-LIKE STELLAR POPULATIONS IN THE MOST LUMINOUS Lyα EMITTERS AT THE EPOCH OF REIONIZATION: SPECTROSCOPIC CONFIRMATION (2015, background): “Both could therefore be tentatively classed as Lyα “blobs” (e.g. Steidel et al. 2000; Matsuda et al. 2004; Steidel et al. 2011).”