Dust, gas and the evolutionary status of the radio galaxy, 8C1435+635,
  at z = 4.25

Ivison, R; Dunlop, J; Hughes, D; Archibald, E; Stevens, J; Holland, W; Robson, I; Eales, S; Rawlings, S; Dey, A; Gear, W

Journal article

Dust, gas and the evolutionary status of the radio galaxy, 8C1435+635, at z = 4.25

Abstract:: We present the results of new rest-frame far-IR observations of the z = 4.25 radio galaxy, 8C1435+635, which not only confirm that it contains an enormous quantity of dust (as first inferred from its mm-wave detection by Ivison 1995) but also allow the first meaningful constraints to be placed on the mass of this dust and associated gas. The new measurements consist of: (i) clear detections of sub-mm continuum emission at 450 and 850um obtained with the new sub-mm bolometer array, SCUBA, on the JCMT, (ii) continuum upper limits at 350, 750 and 175um obtained with SCUBA and the PHT far-IR camera aboard ISO, and (iii) a sensitive upper limit on the CO(4-3) line flux obtained with the IRAM 30-m MRT. The resulting rest-frame 33- to 238-um continuum coverage allows us to deduce that 2E8 Msun of dust at a temperature of 40 +/- 5 K is responsible for the observed mm/sub-mm emission. Using our CO upper limit, which constrains M(H2)/M(dust) to <950, we go on to calculate robust limits on the total gas reserves (H2 + HI) which are thereby constrained to between 4E10 and 1.2E12 Msun. The sub-mm properties of 8C1435+635 are thus strikingly similar to those of the z = 3.80 radio galaxy, 4C41.17, the only other high-redshift galaxy detected to date at sub-mm wavelengths whose properties appear not to be exaggerated by gravitational lensing (Dunlop et al. 1994; Hughes, Dunlop and Rawlings 1997). The inferred gas masses of both objects are sufficiently large to suggest that the formative starbursts of massive elliptical galaxies are still in progress at around z = 4. Observations of complete samples of radio galaxies spanning a range of redshifts and radio luminosities will be required to determine if the spectacular far-IR properties of 8C1435+635 and 4C41.17 are primarily due to their extreme redshifts or their extreme radio luminosities.

Publication status:: Published

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APA Style

Ivison, R., Dunlop, J., Hughes, D., Archibald, E., Stevens, J., Holland, W., Robson, I., Eales, S., Rawlings, S., Dey, A., & Gear, W. (1997). Dust, gas and the evolutionary status of the radio galaxy, 8C1435+635, at z = 4.25. ASTROPHYSICAL JOURNAL, 494(1), 211–217.

MLA Style

Ivison, R., et al. “Dust, Gas and the Evolutionary Status of the Radio Galaxy, 8C1435+635, at z = 4.25.” ASTROPHYSICAL JOURNAL, vol. 494, no. 1, 1997, pp. 211–17.

Chicago Style

Ivison, R, J Dunlop, D Hughes, E Archibald, J Stevens, W Holland, I Robson, et al. 1997. “Dust, Gas and the Evolutionary Status of the Radio Galaxy, 8C1435+635, at z = 4.25.” ASTROPHYSICAL JOURNAL 494 (1): 211–17.
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