NARROWBAND IMAGING OF ESCAPING LYMAN-CONTINUUM EMISSION IN THE SSA22 FIELD<sup>,</sup>

Nestor, Daniel B.; Shapley, Alice E.; Steidel, Charles C.; Siana, Brian

doi:10.1088/0004-637x/736/1/18

Cited by 138 publications

(267 citation statements)

References 68 publications

(183 reference statements)

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“…The vast majority of known high-redshift galaxies are also opaque to their own ionising radiation, as demonstrated by the success of the well-known Lyman-break selection (as emphasised recently in Cooke et al 2014). Only a few tens of objects are detected in the LyC (Iwata et al 2009;Nestor et al 2011Nestor et al , 2013Mostardi et al 2013). A LyC-leaking galaxy has then peculiar rare properties that we describe below.…”

Section: Ionising Continuum Leakage From Galaxiesmentioning

confidence: 79%

Using Lyman-αto detect galaxies that leak Lyman continuum

Verhamme

Orlitová

Schaerer

et al. 2015

A&A

314

439

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Aims. We propose to infer the output of the ionising continuum-leaking properties of galaxies based upon their Lyα line profiles. Methods. We carried out Lyα radiation transfer calculations in two models of H ii regions. These models are porous to ionising continuum escape: 1) we define Lyman-continuum (LyC) optically thin star clusters, in which massive stars produce enough ionising photons to keep the surrounding interstellar medium transparent to the ionising continuum, in other words, almost totally ionised; and 2) we define riddled ionisation-bounded media that are surrounded by neutral interstellar medium, but have holes, which results in a covering fraction lower than unity. Results. The Lyα spectra that emerge from these configurations have distinctive features: 1) a classical asymmetric redshifted profile in the first case, but with a small shift of the profile maximum compared to the systemic redshift (v peak ≤ 150 km s −1 ); 2) a main peak at the systemic redshift in the second case (v peak = 0), with a non-zero Lyα flux bluewards of the systemic redshift as a consequence. If in a galaxy that leaks ionising photons the Lyα component that emerges from the leaking star cluster(s) is assumed to dominate the total Lyα spectrum, the Lyα shape may be used as a pre-selection tool for detecting LyC-leaking galaxies in objects with high spectral resolution Lyα spectra (R ≥ 4000). Our predictions are corroborated by examination of a sample of ten local starbursts with high-resolution HST/COS Lyα spectra that are known in the literature as LyC leakers or leaking candidates. Conclusions. Observations of Lyα profiles at high resolution are expected to show definite signatures revealing the escape of Lyman-continuum photons from star-forming galaxies.

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Section: Ionising Continuum Leakage From Galaxiesmentioning

confidence: 79%

Using Lyman-αto detect galaxies that leak Lyman continuum

Verhamme

Orlitová

Schaerer

et al. 2015

A&A

314

439

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“…In previous articles where z ∼ 3 galaxies were imaged in the LyC, it was shown that emitted ionizing photons can be found at some distance from the center of the galaxies (Iwata et al 2009;Nestor et al 2011). While there is no possible way of acquiring LyC images of Haro 11, we do know that this local galaxy has star-forming regions out to, and beyond, the 30 × 30 LWRS aperture of FUSE.…”

Section: Discussionmentioning

confidence: 99%

“…Iwata et al (2009) and Nestor et al (2011) demonstrated that LyC leakage can be found spatially off-set from the main body of the non-ionizing UV continuum (although some of these detections statistically are likely to be lower redshift contaminants). To estimate the distance from the center at which we would expect most of the ionizing radiation to slip through a picket fence structure in Haro 11, we adopt a simple model with two components -the ionizing stars and the neutral gas.…”

Section: Haro 11mentioning

confidence: 99%

“…To measure escape fractions and investigate the physical properties that allow leakage, we need to study more nearby objects. This can and has been done with groundbased telescopes at z ∼ 3 (e.g., Steidel et al 2001;Shapley et al 2006;Iwata et al 2009;Vanzella et al 2010;Nestor et al 2011), or locally by using space telescopes such as HUT (Leitherer et al 1995), FUSE (Deharveng et al 2001;Bergvall et al 2006;Grimes et al 2007Grimes et al , 2009, GALEX (Cowie et al 2009), and HST (Malkan et al 2003;Siana et al 2007Siana et al , 2010Bridge et al 2010). Of the four only HST and GALEX are still in operation, and until now only HUT and FUSE have been providing wavelength coverage down to 900 Å, such that local galaxies can be studied.…”

Section: Introductionmentioning

confidence: 99%

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Analyzing low signal-to-noise FUSE spectra

Leitet

Bergvall

Piskunov

et al. 2011

A&A

105

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Context. Galaxies are believed to be the main providers of Lyman continuum (LyC) photons during the early phases of the cosmic reionization. Little is known however, when it comes to escape fractions and the mechanisms behind the leakage. To learn more, one may look at local objects, but so far only one low-z galaxy has shown any signs of emitting LyC radiation. With data from the Far Ultraviolet Spectroscopic Explorer (FUSE), we previously found an absolute escape fraction of ionizing photons ( f esc ) of 4-10% for the blue compact galaxy Haro 11. However, using a revised version of the reduction pipeline on the same data set, Grimes and collaborators were unable to confirm this and derived an upper limit of f esc 2% . Aims. We attempt to determine whether Haro 11 is emitting ionizing radiation to a significant level or not. We also investigate the performance of the reduction pipeline for faint targets such as Haro 11, and introduce a new approach to the background subtraction. Methods. The final version of the reduction pipeline, CalFUSE v3.2, was applied to the same Haro 11 data set as the two previous authors used. At these faint flux levels, both FUSE and CalFUSE are pushed to their limits, and a detailed analysis was undertaken to monitor the performance of the pipeline. We show that non-simultaneous background estimates are insuffient when working with data of low signal-to-noise ratio (S /N), and a new background model was developed based on a direct fit to the detector response. Results. We find that one has to be very careful when using CalFUSE v3.2 on low S /N data, and especially when dealing with sources where signal might originate from off-center regions. Applying the new background fit, a significant signal is detected in the LyC in both detector segments covering these wavelengths. Thus, the leakage is confirmed with a flux density of f 900 = 4.0 × 10 −15 erg s −1 cm −2 Å −1 (S /N = 4.6), measured on the airglow free regions in the LyC for the night-only data. This corresponds to an absolute escape fraction of ionizing photons from Haro 11 of f esc = 3.3 ± 0.7%. We confirm these results by investigating the two-dimensional data, the count rates, and the residual flux in C ii λ1036 Å.

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“…It is worth noting that the recent estimates of f esc for L ≥ L * LBGs at 0 ≤ z ≤ 3 are ≤10% (Bridge et al 2010;Cowie et al 2010;Siana et al 2010;Vanzella et al 2010;Boutsia et al 2011): thus, assuming that the Universe is only re-ionized at z ∼ 7 by stars in galaxies, this implies a fast increase of the galaxy escape fraction going to faint luminosities or to high redshifts (but see Nestor et al 2011 for a larger estimate of the escape fraction of L * LBGs at z ∼ 3).…”

Section: The Impact On the Reionization Processmentioning

confidence: 99%

The size-luminosity relation atz = 7 in CANDELS and its implication on reionization

Grazian

Castellano

Fontana

et al. 2012

A&A

101

157

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Context. The exploration of the relation between galaxy sizes and other physical parameters (luminosity, mass, star formation rate) has provided important clues for understanding galaxy formation, but such exploration has until recently been limited to intermediate redshift objects. Aims. We use the currently available CANDELS Deep+Wide surveys in the GOODS-South, UDS and EGS fields, complemented by data from the HUDF09 program, to address the relation between size and luminosity at z ∼ 7. Methods. The six different fields used for this study are characterized by a wide combination of depth and areal coverage, well suited for reducing the biases on the observed size-magnitude plane. From these fields, we select 153 z-band dropout galaxies. Detailed simulations have been carried out for each of these six fields, inserting simulated galaxies at different magnitudes and half light radius in the two dimensional images for all the Hubble Space Telescope (HST) bands available and recovering them as carried out for the real galaxies. These simulations allow us to derive precisely the completeness as a function of size and magnitude and to quantify measurements errors/biases, under the assumption that the 2D profile of z = 7 galaxies is well represented by an exponential disk function. Results. We find in a rather robust way that the half light radius distribution function of z ∼ 7 galaxies fainter than J = 26.6 is peaked at ≤0.1 arcsec (or equivalently 0.5 kpc proper), while at brighter magnitudes high-z galaxies are typically larger than ∼0.15 arcsec. We also find a well defined size-luminosity relation, Rh ∝ L 1/2 . We compute the luminosity function (LF) in the HUDF and P12HUDF fields, finding large spatial variation on the number density of faint galaxies. Adopting the size distribution and the size-luminosity relation found for faint galaxies at z = 7, we derive a mean slope of −1.7 ± 0.1 for the LF of LBGs at this redshift. Conclusions. Using this LF, we find that the number of ionizing photons emitted from galaxies at z ∼ 7 cannot keep the Universe re-ionized if the IGM is clumpy (C HII ≥ 3) and the Lyman continuum escape fraction of high-z LBGs is relatively low ( f esc ≤ 0.3). If these results are confirmed and strengthened by future CANDELS data, in particular by the forthcoming deep observations in GOODS-South and North and the wide field COSMOS, we can put severe limits to the role of galaxies in the reionization of the Universe.

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NARROWBAND IMAGING OF ESCAPING LYMAN-CONTINUUM EMISSION IN THE SSA22 FIELD^,

Cited by 138 publications

References 68 publications

Using Lyman-αto detect galaxies that leak Lyman continuum

Using Lyman-αto detect galaxies that leak Lyman continuum

Analyzing low signal-to-noise FUSE spectra

The size-luminosity relation atz = 7 in CANDELS and its implication on reionization

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NARROWBAND IMAGING OF ESCAPING LYMAN-CONTINUUM EMISSION IN THE SSA22 FIELD,

Cited by 138 publications

References 68 publications

Using Lyman-αto detect galaxies that leak Lyman continuum

Using Lyman-αto detect galaxies that leak Lyman continuum

Analyzing low signal-to-noise FUSE spectra

The size-luminosity relation atz = 7 in CANDELS and its implication on reionization

Contact Info

Product

Resources

About

NARROWBAND IMAGING OF ESCAPING LYMAN-CONTINUUM EMISSION IN THE SSA22 FIELD^,