arXiv subjects

J. Holt

Publications and source records attributed to J. Holt.

60 records · Page 4Linked to original sources

arXiv2003

Highly extinguished emission line outflows in the young radio source PKS 1345+12

(Abridged) We present new, intermediate resolution spectra (~4A) of the compact radio source PKS 1345+12. Our spectra clearly show extended line emission (~20kpc) consistent with the asymmetric halo of diffuse emission observed in optical and infra-red images. In the nucleus we observe complex emission line profiles requiring 3 Gaussian components (narrow, intermediate and broad). The broadest component (FWHM ~2000 km/s) is blue shifted by ~2000 km/s with respect to the galaxy halo and HI absorption. We interpret this as material in outflow. We find evidence for high reddening and measure E(B-V)>0.92 for the broadest component. From [S II]6716,6731 we estimate electron densities of n_e<150cm^{-3}, n_{e}>5300 cm^{-3} and n_{e}>4200 cm^{-3} for the regions emitting the narrow, intermediate and broad components respectively. We calculate a total mass of line emitting gas of M_{gas}<10^6 solar masses. Not all emission line profiles can be reproduced by the same model: [O I]6300,6363 and [S II] require separate, unique models. We argue that PKS 1345+12 is a young radio source whose nuclear regions are enshrouded in a dense cocoon of gas and dust. The radio jets are expanding, sweeping material out of the nuclear regions. Emission originates from three kinematically distinct regions though gradients (e.g. density, ionisation potential, acceleration) must exist across the regions responsible for the emission of the intermediate and broad components.

astro-ph↗

arXiv2003

Emission line studies of young radio sources

We demonstrate the efficiency of high quality optical spectroscopic observations of two compact radio sources, PKS 1549-79 and PKS 1345+12, as a probe of the kinematics and physical conditions in the circumnuclear gas in the early stages of radio source evolution. We outline a schematic model for PKS 1345+12 based on the model for PKS 1549-79 proposed by Tadhunter et al. (2001) in which the young radio source is expanding through a dense and dusty enshrouding cocoon, sweeping material out of the circumnuclear regions.

astro-ph↗

arXiv2002

The impact of the early stages of radio source evolution on the ISM of the host galaxies

The study of both neutral and ionized gas in young radio sources is providing key information on the effect the radio plasma has on the ISM of these objects. We present results obtained for the compact radio sources PKS1549-79, 4C12.50 and PKS1814-63 and for the intermediate-size radio galaxy 3C459. At least in the first two, low ionisation optical emission lines and HI absorption appear to be associated with the extended, but relatively quiescent, dusty cocoon surrounding the nucleus. The [OIII] lines are, on the other hand, mostly associated with the region of interaction between the radio plasma and the ISM, indicating a fast outflow from the canter. A case of fast outflow (up to ~1000 km/s) is also observed in HI in the radio source 4C12.50. As the radio source evolves, any obscuring material along the radio axis is swept aside until, eventually, cavities (of the same kind as observed e.g. in Cygnus A) are hollowed out on either side of the nucleus. We may witness this phase in the evolution of a radio source in the radio galaxy 3C459.

astro-ph↗

arXiv2002

Extreme emission line outflows in the GPS source 4C 12.50 (PKS 1345+12)

We present high resolution spectra (0.7 A/pix) of the GPS source 4C 12.50 with large spectral coverage (~ 4500A) taken with the 4.2m William Herschel Telescope on La Palma. The slit was aligned along PA 160 to include the nucleus and emission line region to the NW. An asymmetric halo extending 20 kpc NW and 12 kpc SE from the nucleus is clearly seen. At the position of the nucleus we observe unusually broad forbidden emission line components (broadest component: FWHM ~ 2000 km s^-1), blue shifted by up to 2000 km s^-1 with respect to the halo of the galaxy and HI absorption. We interpret this as material in outflow. We measure E(B-V) = 1.44 for the broadest, most kinematically disturbed component, corresponding to an actual Hbeta flux 130 times brighter than that measured. We calculate an upper limit for the mass of the line emitting gas of order 10^6 solar masses for both the intermediate and broad components. Our results are consistent with 4C 12.50 being a young radio source.

astro-ph↗

arXiv2001

High-redshift QSOs in the FIRST survey

In a pilot search for high-redshift radio QSOs, we have obtained spectra of 55 FIRST sources (S(1.4GHz) > 1 mJy) with very red (O-E > 3) starlike optical identifications. 10 of the candidates are QSOs with redshifts 3.6 < z < 4.4 (4 previously known), six with z > 4. The remaining 45 candidates comprise: a z = 2.6 BAL QSO; 3 low-redshift galaxies with narrow emission lines; 18 probable radio galaxies; and 23 M stars (mainly misidentifications). The success rate (high-redshift QSOs / spectroscopically-observed candidates) for this search is 1/2 for S(1.4GHz) > 10 mJy, and 1/9 for S(1.4GHz) > 1 mJy. With an effective search area of 4030 deg^2, the surface density of high-redshift (z > 4) QSOs discovered with this technique is 0.0015 deg^-2.

astro-ph↗

arXiv2000

Report of the Beyond the Standard Model Working Group of the 1999 UK Phenomenology Workshop on Collider Physics (Durham)

The Beyond the Standard Model Working Group discussed a variety of topics relating to exotic searches at current and future colliders, and the phenomenology of current models beyond the Standard Model. For example, various supersymmetric (SUSY) and extra dimensions search possibilities and constraints are presented. Fine-tuning implications of SUSY searches are derived. The implications of Higgs (non)-discovery are discussed, as well as the program HDECAY. The individual contributions are included seperately. Much of the enclosed work is original, although some is reviewed.

hep-ph↗