C. Breuck - Academia.edu (original) (raw)

Papers by C. Breuck

Astronomy & Astrophysics, 2012

Context. Supernova 1987A (SN 1987A) in the neighbouring Large Magellanic Cloud offers a superb op... more Context. Supernova 1987A (SN 1987A) in the neighbouring Large Magellanic Cloud offers a superb opportunity to follow the evolution of a supernova and its remnant in unprecedented detail. Recently, far-infrared (far-IR) and sub-mm emission was detected from the direction of SN 1987A, which was interpreted as due to the emission from dust, possibly freshly synthesized in the SN ejecta. Aims. To better constrain the location and hence origin of the far-IR and sub-mm emission in SN 1987A, we have attempted to resolve the object in that part of the electro-magnetic spectrum. Methods. We observed SN 1987A during July-September 2011 with the Atacama Pathfinder EXperiment (APEX), at a wavelength of 350 µm with the Submillimetre APEX Bolometer CAmera (SABOCA) and at 870 µm with the Large APEX BOlometer CAmera (LABOCA). The 350-µm image has superior angular resolution (8 ′′ ) over that of the Herschel Space Observatory 350-µm image (25 ′′ ). The 870-µm observation (at 20 ′′ resolution) is a repetition of a similar observation made in 2007. Results. In both images, at 350 and 870 µm, emission is detected from SN 1987A, and the source is unresolved. The flux densities in the new (2011) measurements are consistent with those measured before with Herschel at 350 µm (in 2010) and with APEX at 870 µm (in 2007). A higher dust temperature (≈ 33 K) and lower dust mass might be possible than what was previously thought.

The Astrophysical Journal, 2010

We present SHARC-2 350 µm data on 20 luminous z ∼ 2 starbursts with S 1.2mm >2 mJy from the Spitz... more We present SHARC-2 350 µm data on 20 luminous z ∼ 2 starbursts with S 1.2mm >2 mJy from the Spitzerselected samples of Lonsdale et al. and Fiolet et al. All the sources were detected, with S 350µm >25 mJy for 18 of them. With the data, we determine precise dust temperatures and luminosities for these galaxies using both single-temperature fits and models with power-law mass-temperature distributions. We derive appropriate formulae to use when optical depths are non-negligible. Our models provide an excellent fit to the 6 µm-2 mm measurements of local starbursts. We find characteristic single-component temperatures T 1 ≃35.5±2.2 K and integrated infrared (IR) luminosities around 10 12.9±0.1 L ⊙ for the SWIRE-selected sources. Molecular gas masses are estimated at ≃4×10 10 M ⊙ , assuming κ 850µm =0.15 m 2 kg −1 and a submillimeter-selected galaxy (SMG)-like gas-to-dust mass ratio. The best-fit models imply 2 kpc emission scales. We also note a tight correlation between rest-frame 1.4 GHz radio and IR luminosities confirming star formation as the predominant power source. The far-IR properties of our sample are indistinguishable from the purely submillimeter-selected populations from current surveys. We therefore conclude that our original selection criteria, based on mid-IR colors and 24 µm flux densities, provides an effective means for the study of SMGs at z∼1.5-2.5.

Monthly Notices of the Royal Astronomical Society, 2009

We report on the identification of the highest redshift submillimetre-selected source currently k... more We report on the identification of the highest redshift submillimetre-selected source currently known: LESS J033229.4−275619. This source was detected in the Large Apex BOlometer CAmera (LABOCA) Extended Chandra Deep Field South (ECDFS) Submillimetre Survey (LESS), a sensitive 870-µm survey (σ 870µm ∼ 1.2 mJy) of the full 30 ′ × 30 ′ ECDFS with the LABOCA camera on the Atacama Pathfinder EXperiment (APEX) telescope. The submillimetre emission is identified with a radio counterpart for which optical spectroscopy provides a redshift of z = 4.76. We show that the bolometric emission is dominated by a starburst with a star formation rate of ∼ 1000 M ⊙ yr −1 , although we also identify a moderate luminosity Active Galactic Nucleus (AGN) in this galaxy. Thus it has characteristics similar to those of z ∼ 2 submillimetre galaxies (SMGs), with a mix of starburst and obscured AGN signatures. This demonstrates that ultraluminous starburst activity is not just restricted to the hosts of the most luminous (and hence rare) QSOs at z ∼ 5, but was also occurring in less extreme galaxies at a time when the Universe was less than 10 per cent of its current age. Assuming that we are seeing the major phase of star formation in this galaxy, then we demonstrate that it would be identified as a luminous distant red galaxy at z ∼ 3 and that the current estimate of the space density of z > 4 SMGs is only sufficient to produce > ∼ 10 per cent of the luminous red galaxy population at these early times. However, this leaves open the possibility that some of these galaxies formed through less intense, but more extended star formation events. If the progenitors of all of the luminous red galaxies at z ∼ 3 go through an ultraluminous starburst at z > ∼ 4 then the required volume density of z > 4 SMGs will exceed that predicted by current galaxy formation models by more than an order of magnitude.

Monthly Notices of the Royal Astronomical Society, 2007

Monthly Notices of the Royal Astronomical Society, 2006

We present the first results from a pilot study to search for distant radio galaxies in the south... more We present the first results from a pilot study to search for distant radio galaxies in the southern hemisphere (δ < −32 • ). Within a 360 deg 2 region of sky, we define a sample of 76 ultra-steep spectrum (USS) radio sources from the 843 MHz Sydney University Molonglo Sky Survey (SUMSS) and 1.4 GHz NRAO VLA Sky Survey (NVSS) radio surveys with α 1400 843 < −1.3 and S 1400 >15 mJy. We observed 71 sources without bright optical or near-infrared counterparts at 1.385 GHz with the ATCA, providing ∼5 ′′ resolution images and sub-arcsec positional accuracy. To identify their host galaxies, we obtained near-IR K−band images with IRIS2 at the AAT and SofI at the NTT. We identify 92% of the USS sources down to K ∼ 20.5. The SUMSS-NVSS USS sources have a surface density more than 4 times higher than USS sources selected at lower frequencies. This is due to the higher effective selection frequency, and the well-matched resolutions of both surveys constructed using the same source fitting algorithm. The scattering of α > −1.3 sources into the USS sample due to spectral index uncertainties can account for only 35% of the observed USS sources.

Monthly Notices of the Royal Astronomical Society, 2007

The morphological and spectroscopic properties of the giant (>60 kpc) Lyα nebulae associated with... more The morphological and spectroscopic properties of the giant (>60 kpc) Lyα nebulae associated with three radio galaxies at z ∼2.5 ( MRC 1558-003, MRC 2025-218 and MRC 0140-257) have been investigated using integral field spectroscopic data obtained with VIMOS on VLT.

Astronomy and Astrophysics, 2001

We present spectroscopic observations of the rest-frame UV line emission around radio galaxy MRC ... more We present spectroscopic observations of the rest-frame UV line emission around radio galaxy MRC 2104-242 at z = 2.49, obtained with FORS1 on VLT Antu. The morphology of the halo is dominated by two spatially resolved regions. Lyα is extended by >12 ′′ along the radio axis, C IV and He II are extended by ∼8 ′′ . The overall spectrum is typical for that of high redshift radio galaxies. The most striking spatial variation is that N V is present in the spectrum of the region associated with the center of the galaxy hosting the radio source, the northern region, while absent in the southern region. Assuming that the gas is photoionized by a hidden quasar, the difference in N V emission can be explained by a metallicity gradient within the halo, with the northern region having a metallicity of Z ≈ 1.5 Z ⊙ and Z ≤ 0.4 Z ⊙ for the southern region. This is consistent with a scenario in which the gas is associated with a massive cooling flow or originates from the debris of the merging of two or more galaxies.

Astronomy and Astrophysics Supplement Series, 2000

Since radio sources with Ultra Steep Spectra (USS; α ∼ < −1.30; S ∝ ν α ) are efficient tracers o... more Since radio sources with Ultra Steep Spectra (USS; α ∼ < −1.30; S ∝ ν α ) are efficient tracers of high redshift radio galaxies (HzRGs), we have defined three samples of such USS sources using the recently completed WENSS, TEXAS, MRC, NVSS and PMN radiosurveys. Our combined sample contains 669 sources with S 1400 > 10 mJy and covers virtually the entire sky outside the Galactic plane (|b| > 15 • ). For our 2 largest samples, covering δ > −35 • , we selected only sources with angular sizes Θ < 1 ′ . For 410 sources, we present radio-maps with 0. ′′ 3 to ∼5 ′′ resolution from VLA and ATCA observations or from the FIRST survey, which allows the optical identification of these radio sources.

Monthly Notices of the Royal Astronomical Society, 2014

We present a CO(1-0) survey for cold molecular gas in a representative sample of 13 high-z radio ... more We present a CO(1-0) survey for cold molecular gas in a representative sample of 13 high-z radio galaxies (HzRGs) at 1.4 < z < 2.8, using the Australia Telescope Compact Array. We detect CO(1-0) emission associated with five sources: MRC 0114-211, MRC 0152-209, MRC 0156-252, MRC 1138-262 and MRC 2048-272. The CO(1-0) luminosities are in the range L CO ∼ (5 − 9) × 10 10 K km s −1 pc 2 . For MRC 0152-209 and MRC 1138-262 part of the CO(1-0) emission coincides with the radio galaxy, while part is spread on scales of tens of kpc and likely associated with galaxy mergers. The molecular gas mass derived for these two systems is M H2 ∼ 6 × 10 10 M (M H2 /L CO = 0.8). For the remaining three CO-detected sources, the CO(1-0) emission is located in the halo (∼50-kpc) environment. These three HzRGs are among the fainter far-IR emitters in our sample, suggesting that similar reservoirs of cold molecular halo gas may have been missed in earlier studies due to pre-selection of IR-bright sources. In all three cases the CO(1-0) is aligned along the radio axis and found beyond the brightest radio hot-spot, in a region devoid of 4.5µm emission in Spitzer imaging. The CO(1-0) profiles are broad, with velocity widths of ∼ 1000 -3600 km s −1 . We discuss several possible scenarios to explain these halo reservoirs of CO(1-0). Following these results, we complement our CO(1-0) study with detections of extended CO from the literature and find at marginal statistical significance (95% level) that CO in HzRGs is preferentially aligned towards the radio jet axis. For the eight sources in which we do not detect CO(1-0), we set realistic upper limits of L CO ∼ 3 − 4 × 10 10 K km s −1 pc 2 . Our survey reveals a CO(1-0) detection rate of 38%, allowing us to compare the CO(1-0) content of HzRGs with that of other types of high-z galaxies.

Astronomy & Astrophysics, 2012

Context. Supernova 1987A (SN 1987A) in the neighbouring Large Magellanic Cloud offers a superb op... more Context. Supernova 1987A (SN 1987A) in the neighbouring Large Magellanic Cloud offers a superb opportunity to follow the evolution of a supernova and its remnant in unprecedented detail. Recently, far-infrared (far-IR) and sub-mm emission was detected from the direction of SN 1987A, which was interpreted as due to the emission from dust, possibly freshly synthesized in the SN ejecta. Aims. To better constrain the location and hence origin of the far-IR and sub-mm emission in SN 1987A, we have attempted to resolve the object in that part of the electro-magnetic spectrum. Methods. We observed SN 1987A during July-September 2011 with the Atacama Pathfinder EXperiment (APEX), at a wavelength of 350 µm with the Submillimetre APEX Bolometer CAmera (SABOCA) and at 870 µm with the Large APEX BOlometer CAmera (LABOCA). The 350-µm image has superior angular resolution (8 ′′ ) over that of the Herschel Space Observatory 350-µm image (25 ′′ ). The 870-µm observation (at 20 ′′ resolution) is a repetition of a similar observation made in 2007. Results. In both images, at 350 and 870 µm, emission is detected from SN 1987A, and the source is unresolved. The flux densities in the new (2011) measurements are consistent with those measured before with Herschel at 350 µm (in 2010) and with APEX at 870 µm (in 2007). A higher dust temperature (≈ 33 K) and lower dust mass might be possible than what was previously thought.

The Astrophysical Journal, 2010

We present SHARC-2 350 µm data on 20 luminous z ∼ 2 starbursts with S 1.2mm >2 mJy from the Spitz... more We present SHARC-2 350 µm data on 20 luminous z ∼ 2 starbursts with S 1.2mm >2 mJy from the Spitzerselected samples of Lonsdale et al. and Fiolet et al. All the sources were detected, with S 350µm >25 mJy for 18 of them. With the data, we determine precise dust temperatures and luminosities for these galaxies using both single-temperature fits and models with power-law mass-temperature distributions. We derive appropriate formulae to use when optical depths are non-negligible. Our models provide an excellent fit to the 6 µm-2 mm measurements of local starbursts. We find characteristic single-component temperatures T 1 ≃35.5±2.2 K and integrated infrared (IR) luminosities around 10 12.9±0.1 L ⊙ for the SWIRE-selected sources. Molecular gas masses are estimated at ≃4×10 10 M ⊙ , assuming κ 850µm =0.15 m 2 kg −1 and a submillimeter-selected galaxy (SMG)-like gas-to-dust mass ratio. The best-fit models imply 2 kpc emission scales. We also note a tight correlation between rest-frame 1.4 GHz radio and IR luminosities confirming star formation as the predominant power source. The far-IR properties of our sample are indistinguishable from the purely submillimeter-selected populations from current surveys. We therefore conclude that our original selection criteria, based on mid-IR colors and 24 µm flux densities, provides an effective means for the study of SMGs at z∼1.5-2.5.

Monthly Notices of the Royal Astronomical Society, 2009

We report on the identification of the highest redshift submillimetre-selected source currently k... more We report on the identification of the highest redshift submillimetre-selected source currently known: LESS J033229.4−275619. This source was detected in the Large Apex BOlometer CAmera (LABOCA) Extended Chandra Deep Field South (ECDFS) Submillimetre Survey (LESS), a sensitive 870-µm survey (σ 870µm ∼ 1.2 mJy) of the full 30 ′ × 30 ′ ECDFS with the LABOCA camera on the Atacama Pathfinder EXperiment (APEX) telescope. The submillimetre emission is identified with a radio counterpart for which optical spectroscopy provides a redshift of z = 4.76. We show that the bolometric emission is dominated by a starburst with a star formation rate of ∼ 1000 M ⊙ yr −1 , although we also identify a moderate luminosity Active Galactic Nucleus (AGN) in this galaxy. Thus it has characteristics similar to those of z ∼ 2 submillimetre galaxies (SMGs), with a mix of starburst and obscured AGN signatures. This demonstrates that ultraluminous starburst activity is not just restricted to the hosts of the most luminous (and hence rare) QSOs at z ∼ 5, but was also occurring in less extreme galaxies at a time when the Universe was less than 10 per cent of its current age. Assuming that we are seeing the major phase of star formation in this galaxy, then we demonstrate that it would be identified as a luminous distant red galaxy at z ∼ 3 and that the current estimate of the space density of z > 4 SMGs is only sufficient to produce > ∼ 10 per cent of the luminous red galaxy population at these early times. However, this leaves open the possibility that some of these galaxies formed through less intense, but more extended star formation events. If the progenitors of all of the luminous red galaxies at z ∼ 3 go through an ultraluminous starburst at z > ∼ 4 then the required volume density of z > 4 SMGs will exceed that predicted by current galaxy formation models by more than an order of magnitude.

Monthly Notices of the Royal Astronomical Society, 2007

Monthly Notices of the Royal Astronomical Society, 2006

We present the first results from a pilot study to search for distant radio galaxies in the south... more We present the first results from a pilot study to search for distant radio galaxies in the southern hemisphere (δ < −32 • ). Within a 360 deg 2 region of sky, we define a sample of 76 ultra-steep spectrum (USS) radio sources from the 843 MHz Sydney University Molonglo Sky Survey (SUMSS) and 1.4 GHz NRAO VLA Sky Survey (NVSS) radio surveys with α 1400 843 < −1.3 and S 1400 >15 mJy. We observed 71 sources without bright optical or near-infrared counterparts at 1.385 GHz with the ATCA, providing ∼5 ′′ resolution images and sub-arcsec positional accuracy. To identify their host galaxies, we obtained near-IR K−band images with IRIS2 at the AAT and SofI at the NTT. We identify 92% of the USS sources down to K ∼ 20.5. The SUMSS-NVSS USS sources have a surface density more than 4 times higher than USS sources selected at lower frequencies. This is due to the higher effective selection frequency, and the well-matched resolutions of both surveys constructed using the same source fitting algorithm. The scattering of α > −1.3 sources into the USS sample due to spectral index uncertainties can account for only 35% of the observed USS sources.

Monthly Notices of the Royal Astronomical Society, 2007

The morphological and spectroscopic properties of the giant (>60 kpc) Lyα nebulae associated with... more The morphological and spectroscopic properties of the giant (>60 kpc) Lyα nebulae associated with three radio galaxies at z ∼2.5 ( MRC 1558-003, MRC 2025-218 and MRC 0140-257) have been investigated using integral field spectroscopic data obtained with VIMOS on VLT.

Astronomy and Astrophysics, 2001

We present spectroscopic observations of the rest-frame UV line emission around radio galaxy MRC ... more We present spectroscopic observations of the rest-frame UV line emission around radio galaxy MRC 2104-242 at z = 2.49, obtained with FORS1 on VLT Antu. The morphology of the halo is dominated by two spatially resolved regions. Lyα is extended by >12 ′′ along the radio axis, C IV and He II are extended by ∼8 ′′ . The overall spectrum is typical for that of high redshift radio galaxies. The most striking spatial variation is that N V is present in the spectrum of the region associated with the center of the galaxy hosting the radio source, the northern region, while absent in the southern region. Assuming that the gas is photoionized by a hidden quasar, the difference in N V emission can be explained by a metallicity gradient within the halo, with the northern region having a metallicity of Z ≈ 1.5 Z ⊙ and Z ≤ 0.4 Z ⊙ for the southern region. This is consistent with a scenario in which the gas is associated with a massive cooling flow or originates from the debris of the merging of two or more galaxies.

Astronomy and Astrophysics Supplement Series, 2000

Since radio sources with Ultra Steep Spectra (USS; α ∼ < −1.30; S ∝ ν α ) are efficient tracers o... more Since radio sources with Ultra Steep Spectra (USS; α ∼ < −1.30; S ∝ ν α ) are efficient tracers of high redshift radio galaxies (HzRGs), we have defined three samples of such USS sources using the recently completed WENSS, TEXAS, MRC, NVSS and PMN radiosurveys. Our combined sample contains 669 sources with S 1400 > 10 mJy and covers virtually the entire sky outside the Galactic plane (|b| > 15 • ). For our 2 largest samples, covering δ > −35 • , we selected only sources with angular sizes Θ < 1 ′ . For 410 sources, we present radio-maps with 0. ′′ 3 to ∼5 ′′ resolution from VLA and ATCA observations or from the FIRST survey, which allows the optical identification of these radio sources.

Monthly Notices of the Royal Astronomical Society, 2014

We present a CO(1-0) survey for cold molecular gas in a representative sample of 13 high-z radio ... more We present a CO(1-0) survey for cold molecular gas in a representative sample of 13 high-z radio galaxies (HzRGs) at 1.4 < z < 2.8, using the Australia Telescope Compact Array. We detect CO(1-0) emission associated with five sources: MRC 0114-211, MRC 0152-209, MRC 0156-252, MRC 1138-262 and MRC 2048-272. The CO(1-0) luminosities are in the range L CO ∼ (5 − 9) × 10 10 K km s −1 pc 2 . For MRC 0152-209 and MRC 1138-262 part of the CO(1-0) emission coincides with the radio galaxy, while part is spread on scales of tens of kpc and likely associated with galaxy mergers. The molecular gas mass derived for these two systems is M H2 ∼ 6 × 10 10 M (M H2 /L CO = 0.8). For the remaining three CO-detected sources, the CO(1-0) emission is located in the halo (∼50-kpc) environment. These three HzRGs are among the fainter far-IR emitters in our sample, suggesting that similar reservoirs of cold molecular halo gas may have been missed in earlier studies due to pre-selection of IR-bright sources. In all three cases the CO(1-0) is aligned along the radio axis and found beyond the brightest radio hot-spot, in a region devoid of 4.5µm emission in Spitzer imaging. The CO(1-0) profiles are broad, with velocity widths of ∼ 1000 -3600 km s −1 . We discuss several possible scenarios to explain these halo reservoirs of CO(1-0). Following these results, we complement our CO(1-0) study with detections of extended CO from the literature and find at marginal statistical significance (95% level) that CO in HzRGs is preferentially aligned towards the radio jet axis. For the eight sources in which we do not detect CO(1-0), we set realistic upper limits of L CO ∼ 3 − 4 × 10 10 K km s −1 pc 2 . Our survey reveals a CO(1-0) detection rate of 38%, allowing us to compare the CO(1-0) content of HzRGs with that of other types of high-z galaxies.