X-ray properties of He II lambda 1640 emitting galaxies in VANDELS
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X-ray properties of He II lambda 1640 emitting galaxies in VANDELS. / Saxena, A.; Pentericci, L.; Schaerer, D.; Schneider, R.; Amorin, R.; Bongiorno, A.; Calabro, A.; Castellano, M.; Cimatti, A.; Cullen, F.; Fontana, A.; Fynbo, J. P. U.; Hathi, N.; McLeod, D. J.; Talia, M.; Zamorani, G.
In: Monthly Notices of the Royal Astronomical Society, Vol. 496, No. 3, 23.06.2020, p. 3796-3807.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - X-ray properties of He II lambda 1640 emitting galaxies in VANDELS
AU - Saxena, A.
AU - Pentericci, L.
AU - Schaerer, D.
AU - Schneider, R.
AU - Amorin, R.
AU - Bongiorno, A.
AU - Calabro, A.
AU - Castellano, M.
AU - Cimatti, A.
AU - Cullen, F.
AU - Fontana, A.
AU - Fynbo, J. P. U.
AU - Hathi, N.
AU - McLeod, D. J.
AU - Talia, M.
AU - Zamorani, G.
PY - 2020/6/23
Y1 - 2020/6/23
N2 - We explore X-ray emission from a sample of 18 He II lambda 1640 emitting star-forming galaxies at z similar to 2.3-3.6 from the VANDELS survey in the Chandra Deep Field South, to set constraints on the role of X-ray sources in powering the He II emission. We find that 4 He II emitters have tentative detections with S/N similar to 2 and have X-ray luminosities, L-X = 1.5-4.9 x 10(41) erg s(-1). The stacked luminosity of all 18 He II emitters is 2.6 x 10(41) erg s(-1), and that of a subset of 13 narrow He II emitters (FHWM(He II) <1000 km s(-1)) is 3.1 x 10(41) erg s(-1). We also measure stacked LX for non-He II emitters through bootstrapping of matched samples, and find L-X = 2.5 x 10(41) erg s(-1), which is not significantly different from LX measured for He II emitters. The LX per star formation rate for He II emitters (log (L-X/SFR) similar to 40.0) and nonemitters (log (L-X/SFR) similar to 39.9) are also comparable and in line with the redshift evolution and metallicity dependence predicted by models. Due to the non-significant difference between the X-ray emission from galaxies with and without He II, we conclude that X-ray binaries or weak or obscured active galactic nuclei are unlikely to be the dominant producers of He II ionizing photons in VANDELS star-forming galaxies at z similar to 3. Given the comparable physical properties of both He II emitters and non-emitters reported previously, alternative He II ionizing mechanisms such as localized low-metallicity stellar populations, Pop-III stars, etc. may need to be explored.
AB - We explore X-ray emission from a sample of 18 He II lambda 1640 emitting star-forming galaxies at z similar to 2.3-3.6 from the VANDELS survey in the Chandra Deep Field South, to set constraints on the role of X-ray sources in powering the He II emission. We find that 4 He II emitters have tentative detections with S/N similar to 2 and have X-ray luminosities, L-X = 1.5-4.9 x 10(41) erg s(-1). The stacked luminosity of all 18 He II emitters is 2.6 x 10(41) erg s(-1), and that of a subset of 13 narrow He II emitters (FHWM(He II) <1000 km s(-1)) is 3.1 x 10(41) erg s(-1). We also measure stacked LX for non-He II emitters through bootstrapping of matched samples, and find L-X = 2.5 x 10(41) erg s(-1), which is not significantly different from LX measured for He II emitters. The LX per star formation rate for He II emitters (log (L-X/SFR) similar to 40.0) and nonemitters (log (L-X/SFR) similar to 39.9) are also comparable and in line with the redshift evolution and metallicity dependence predicted by models. Due to the non-significant difference between the X-ray emission from galaxies with and without He II, we conclude that X-ray binaries or weak or obscured active galactic nuclei are unlikely to be the dominant producers of He II ionizing photons in VANDELS star-forming galaxies at z similar to 3. Given the comparable physical properties of both He II emitters and non-emitters reported previously, alternative He II ionizing mechanisms such as localized low-metallicity stellar populations, Pop-III stars, etc. may need to be explored.
KW - galaxies: evolution
KW - galaxies: high-redshift
KW - X-rays: binaries
KW - STAR-FORMING GALAXIES
KW - EMISSION-LINE SPECTRA
KW - POPULATION III
KW - MASS
KW - METALLICITY
KW - DENSITY
KW - ALPHA
KW - REIONIZATION
KW - SIGNATURES
KW - UNIVERSE
U2 - 10.1093/mnras/staa1805
DO - 10.1093/mnras/staa1805
M3 - Journal article
VL - 496
SP - 3796
EP - 3807
JO - Royal Astronomical Society. Monthly Notices
JF - Royal Astronomical Society. Monthly Notices
SN - 0035-8711
IS - 3
ER -
ID: 252154829