VLT spectroscopy of the z=4.11 radio galaxy TN J1338-1942

Carlos De Breuck, Wil Van Breugel, Dante Minniti, George Miley, Huub Röttgering, S. A. Stanford, Chris Carilli

Resultado de la investigación: Article

32 Citas (Scopus)

Resumen

We present optical, infrared and radio data of the z = 4.11 radio galaxy TN J1338-1942 including an intermediate resolution spectrum obtained with FORS1 on the VLT Antu telescope. TN J1338-1942 was the first z > 4 radio galaxy to be discovered in the southern hemisphere and is one of the most luminous Lyα objects in its class. The Lyα and rest-frame optical emission appear co-spatial with the brightest radio hotspot of this very asymmetric radio source, suggesting extremely strong interaction with dense ambient clouds. The Lyα is spatially extended by ∼4″(30 kpc), has an enormous rest-frame equivalent width, Wrestλ = 210 ± 50 Å, and has a spectral profile that is very asymmetric with a deficit towards the blue. We interpret this blue-ward asymmetry as being due to absorption of the Lyα photons by cold gas in a turbulent halo surrounding the radio galaxy and show that the required neutral hydrogen column density must be in the range 3.5-13 × 1019 cm-2. The two-dimensional spectrum indicates that the extent of the absorbing gas is comparable (or even larger) than the 4″(30 kpc) Lyα emitting region. The VLT observations are sufficiently sensitive to detect the continuum flux both blue-ward and red-ward of the Lyα emission, allowing us to measure the Lyα forest continuum break (Lyα 'discontinuity', DA) and the Lyman limit. We measure a DA = 0.37 ± 0.1. which is ∼0.2 lower than the values found for quasars at this redshift. We interpret this difference as possibly due to a bias towards large DA introduced in high-redshift quasar samples that are selected on the basis of specific optical colors. If such a bias would exist in optically selected quasars, - and even in samples of Lyman break galaxies -, then the space density of both classes of object will be underestimated. Furthermore, the average H I column density along cosmological lines of sight as determined using quasar absorption lines would be overestimated. Because of their radio-based selection, we argue that z > 4 radio galaxies are excellent objects for investigating DA statistics.

Idioma originalEnglish
PublicaciónAstronomy and Astrophysics
Volumen352
N.º1
EstadoPublished - 1 dic 1999

Huella dactilar

radio galaxies
quasars
spectroscopy
radio
continuums
space density
cold gas
Southern Hemisphere
line of sight
light emission
halos
discontinuity
asymmetry
statistics
telescopes
galaxies
color
photons
hydrogen
profiles

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Citar esto

De Breuck, C., Van Breugel, W., Minniti, D., Miley, G., Röttgering, H., Stanford, S. A., & Carilli, C. (1999). VLT spectroscopy of the z=4.11 radio galaxy TN J1338-1942. Astronomy and Astrophysics, 352(1).
De Breuck, Carlos ; Van Breugel, Wil ; Minniti, Dante ; Miley, George ; Röttgering, Huub ; Stanford, S. A. ; Carilli, Chris. / VLT spectroscopy of the z=4.11 radio galaxy TN J1338-1942. En: Astronomy and Astrophysics. 1999 ; Vol. 352, N.º 1.
@article{30063396ad744b65af4c4fc2aef0db84,
title = "VLT spectroscopy of the z=4.11 radio galaxy TN J1338-1942",
abstract = "We present optical, infrared and radio data of the z = 4.11 radio galaxy TN J1338-1942 including an intermediate resolution spectrum obtained with FORS1 on the VLT Antu telescope. TN J1338-1942 was the first z > 4 radio galaxy to be discovered in the southern hemisphere and is one of the most luminous Lyα objects in its class. The Lyα and rest-frame optical emission appear co-spatial with the brightest radio hotspot of this very asymmetric radio source, suggesting extremely strong interaction with dense ambient clouds. The Lyα is spatially extended by ∼4″(30 kpc), has an enormous rest-frame equivalent width, Wrestλ = 210 ± 50 {\AA}, and has a spectral profile that is very asymmetric with a deficit towards the blue. We interpret this blue-ward asymmetry as being due to absorption of the Lyα photons by cold gas in a turbulent halo surrounding the radio galaxy and show that the required neutral hydrogen column density must be in the range 3.5-13 × 1019 cm-2. The two-dimensional spectrum indicates that the extent of the absorbing gas is comparable (or even larger) than the 4″(30 kpc) Lyα emitting region. The VLT observations are sufficiently sensitive to detect the continuum flux both blue-ward and red-ward of the Lyα emission, allowing us to measure the Lyα forest continuum break (Lyα 'discontinuity', DA) and the Lyman limit. We measure a DA = 0.37 ± 0.1. which is ∼0.2 lower than the values found for quasars at this redshift. We interpret this difference as possibly due to a bias towards large DA introduced in high-redshift quasar samples that are selected on the basis of specific optical colors. If such a bias would exist in optically selected quasars, - and even in samples of Lyman break galaxies -, then the space density of both classes of object will be underestimated. Furthermore, the average H I column density along cosmological lines of sight as determined using quasar absorption lines would be overestimated. Because of their radio-based selection, we argue that z > 4 radio galaxies are excellent objects for investigating DA statistics.",
keywords = "Cosmology: observations, Galaxies: active, Galaxies: individual: TN J1338-1942",
author = "{De Breuck}, Carlos and {Van Breugel}, Wil and Dante Minniti and George Miley and Huub R{\"o}ttgering and Stanford, {S. A.} and Chris Carilli",
year = "1999",
month = "12",
day = "1",
language = "English",
volume = "352",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
number = "1",

}

De Breuck, C, Van Breugel, W, Minniti, D, Miley, G, Röttgering, H, Stanford, SA & Carilli, C 1999, 'VLT spectroscopy of the z=4.11 radio galaxy TN J1338-1942', Astronomy and Astrophysics, vol. 352, n.º 1.

VLT spectroscopy of the z=4.11 radio galaxy TN J1338-1942. / De Breuck, Carlos; Van Breugel, Wil; Minniti, Dante; Miley, George; Röttgering, Huub; Stanford, S. A.; Carilli, Chris.

En: Astronomy and Astrophysics, Vol. 352, N.º 1, 01.12.1999.

Resultado de la investigación: Article

TY - JOUR

T1 - VLT spectroscopy of the z=4.11 radio galaxy TN J1338-1942

AU - De Breuck, Carlos

AU - Van Breugel, Wil

AU - Minniti, Dante

AU - Miley, George

AU - Röttgering, Huub

AU - Stanford, S. A.

AU - Carilli, Chris

PY - 1999/12/1

Y1 - 1999/12/1

N2 - We present optical, infrared and radio data of the z = 4.11 radio galaxy TN J1338-1942 including an intermediate resolution spectrum obtained with FORS1 on the VLT Antu telescope. TN J1338-1942 was the first z > 4 radio galaxy to be discovered in the southern hemisphere and is one of the most luminous Lyα objects in its class. The Lyα and rest-frame optical emission appear co-spatial with the brightest radio hotspot of this very asymmetric radio source, suggesting extremely strong interaction with dense ambient clouds. The Lyα is spatially extended by ∼4″(30 kpc), has an enormous rest-frame equivalent width, Wrestλ = 210 ± 50 Å, and has a spectral profile that is very asymmetric with a deficit towards the blue. We interpret this blue-ward asymmetry as being due to absorption of the Lyα photons by cold gas in a turbulent halo surrounding the radio galaxy and show that the required neutral hydrogen column density must be in the range 3.5-13 × 1019 cm-2. The two-dimensional spectrum indicates that the extent of the absorbing gas is comparable (or even larger) than the 4″(30 kpc) Lyα emitting region. The VLT observations are sufficiently sensitive to detect the continuum flux both blue-ward and red-ward of the Lyα emission, allowing us to measure the Lyα forest continuum break (Lyα 'discontinuity', DA) and the Lyman limit. We measure a DA = 0.37 ± 0.1. which is ∼0.2 lower than the values found for quasars at this redshift. We interpret this difference as possibly due to a bias towards large DA introduced in high-redshift quasar samples that are selected on the basis of specific optical colors. If such a bias would exist in optically selected quasars, - and even in samples of Lyman break galaxies -, then the space density of both classes of object will be underestimated. Furthermore, the average H I column density along cosmological lines of sight as determined using quasar absorption lines would be overestimated. Because of their radio-based selection, we argue that z > 4 radio galaxies are excellent objects for investigating DA statistics.

AB - We present optical, infrared and radio data of the z = 4.11 radio galaxy TN J1338-1942 including an intermediate resolution spectrum obtained with FORS1 on the VLT Antu telescope. TN J1338-1942 was the first z > 4 radio galaxy to be discovered in the southern hemisphere and is one of the most luminous Lyα objects in its class. The Lyα and rest-frame optical emission appear co-spatial with the brightest radio hotspot of this very asymmetric radio source, suggesting extremely strong interaction with dense ambient clouds. The Lyα is spatially extended by ∼4″(30 kpc), has an enormous rest-frame equivalent width, Wrestλ = 210 ± 50 Å, and has a spectral profile that is very asymmetric with a deficit towards the blue. We interpret this blue-ward asymmetry as being due to absorption of the Lyα photons by cold gas in a turbulent halo surrounding the radio galaxy and show that the required neutral hydrogen column density must be in the range 3.5-13 × 1019 cm-2. The two-dimensional spectrum indicates that the extent of the absorbing gas is comparable (or even larger) than the 4″(30 kpc) Lyα emitting region. The VLT observations are sufficiently sensitive to detect the continuum flux both blue-ward and red-ward of the Lyα emission, allowing us to measure the Lyα forest continuum break (Lyα 'discontinuity', DA) and the Lyman limit. We measure a DA = 0.37 ± 0.1. which is ∼0.2 lower than the values found for quasars at this redshift. We interpret this difference as possibly due to a bias towards large DA introduced in high-redshift quasar samples that are selected on the basis of specific optical colors. If such a bias would exist in optically selected quasars, - and even in samples of Lyman break galaxies -, then the space density of both classes of object will be underestimated. Furthermore, the average H I column density along cosmological lines of sight as determined using quasar absorption lines would be overestimated. Because of their radio-based selection, we argue that z > 4 radio galaxies are excellent objects for investigating DA statistics.

KW - Cosmology: observations

KW - Galaxies: active

KW - Galaxies: individual: TN J1338-1942

UR - http://www.scopus.com/inward/record.url?scp=0012963625&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0012963625

VL - 352

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

IS - 1

ER -

De Breuck C, Van Breugel W, Minniti D, Miley G, Röttgering H, Stanford SA y otros. VLT spectroscopy of the z=4.11 radio galaxy TN J1338-1942. Astronomy and Astrophysics. 1999 dic 1;352(1).