Publications by Leah Morabito

LoTSS DR1: Double-double radio galaxies in the HETDEX field


VH Mahatma, MJ Hardcastle, WL Williams, PN Best, JH Croston, K Duncan, B Mingo, R Morganti, M Brienza, RK Cochrane, G Gurkan, JJ Harwood, MJ Jarvis, M Jamrozy, N Jurlin, LK Morabito, HJA Rottgering, J Sabater, TW Shimwell, DJB Smith, A Shulevski, C Tasse

The origin of radio emission in broad absorption line quasars: Results from the LOFAR Two-metre Sky Survey

Astronomy and Astrophysics EDP Sciences 622 (2018) A15

L Morabito, J Matthews, G Gurkan, P Best, M Jarvis, I Prandoni, K Duncan, M Kunert-Bajraszewska, M Hardcastle, A Mechev, J Sabeter, S Mooney, H Rottgering, T Shimwell, D Smith, C Tasse, W Williams

We present a study of the low-frequency radio properties of broad absorption line quasars (BALQSOs) from the LOFAR Two-metre Sky-Survey Data Release 1 (LDR1). The value-added LDR1 catalogue contains Pan-STARRS counterparts, which we match with the Sloan Digital Sky Survey (SDSS) DR7 and DR12 quasar catalogues. We find that BALQSOs are twice as likely to be detected at 144 MHz than their non-BAL counterparts, and BALQSOs with low-ionisation species present in their spectra are three times more likely to be detected than those with only high-ionisation species. The BALQSO fraction at 144 MHz is constant with increasing radio luminosity, which is inconsistent with previous results at 1.4 GHz, indicating that observations at the different frequencies may be tracing different sources of radio emission. We cross-match radio sources between the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) survey and LDR1, which provides a bridge via the LDR1 Pan-STARRS counterparts to identify BALQSOs in SDSS. Consequently we expand the sample of BALQSOs detected in FIRST by a factor of three. The LDR1-detected BALQSOs in our sample are almost exclusively radio-quiet (log(R144 MHz) <2), with radio sizes at 144 MHz typically less than 200 kpc; these radio sizes tend to be larger than those at 1.4 GHz, suggesting more extended radio emission at low frequencies. We find that although the radio detection fraction increases with increasing balnicity index (BI), there is no correlation between BI and either low-frequency radio power or radio-loudness. This suggests that both radio emission and BI may be linked to the same underlying process, but are spatially distinct phenomena.

The environments of radio-loud AGN from the LOFAR Two-Metre Sky Survey (LoTSS)


JH Croston, MJ Hardcastle, B Mingo, PN Best, J Sabater, TM Shimwell, WL Williams, KJ Duncan, HJA Rottgering, M Brienza, G Gurkan, J Ineson, GK Miley, LM Morabito, SP O'Sullivan, I Prandoni

Radio-loud AGN in the first LoTSS data release The lifetimes and environmental impact of jet-driven sources


MJ Hardcastle, WL Williams, PN Best, JH Croston, KJ Duncan, HJA Rottgering, J Sabater, TW Shimwell, C Tasse, JR Callingham, RK Cochrane, F de Gasperin, G Gurkan, MJ Jarvis, V Mahatma, GK Miley, B Mingo, S Mooney, LK Morabito, SP O'Sullivan, I Prandoni, A Shulevski, DJB Smith

LoTSS DR1: Double-double radio galaxies in the HETDEX field

Astronomy and Astrophysics EDP Sciences (2019)

VH Mahatma, MJ Hardcastle, WL Williams, PN Best, JH Croston, K Duncan, B Mingo, R Morganti, M Brienza, RK Cochrane, G Gürkan, JJ Harwood, MJ Jarvis, M Jamrozy, N Jurlin, LK Morabito, HJA Röttgering, J Sabater, TW Shimwell, DJB Smith, A Shulevski, C Tasse

Double-double radio galaxies (DDRGs) represent a short but unique phase in the life-cycle of some of the most powerful radio-loud active galactic nuclei (RLAGN). These galaxies display large-scale remnant radio plasma in the intergalactic medium left behind by a past episode of active galactic nuclei (AGN) activity, and meanwhile, the radio jets have restarted in a new episode. The knowledge of what causes the jets to switch off and restart is crucial to our understanding of galaxy evolution, while it is important to know if DDRGs form a host galaxy dichotomy relative to RLAGN. We utilised the LOFAR Two-Metre Sky Survey DR1, using a visual identification method to compile a sample of morphologically selected candidate DDRGs, showing two pairs of radio lobes. To confirm the restarted nature in each of the candidate sources, we obtained follow-up observations with the VLA at higher resolution to observe the inner lobes or restarted jets, the confirmation of which created a robust sample of 33 DDRGs. We created a comparison sample of 777 RLAGN from the DR1 catalogue, and compared the optical and infrared magnitudes and colours of their host galaxies. We find that there is no statistically significant difference in the brightness of the host galaxies between double-doubles and single-cycle RLAGN. The DDRG and RLAGN samples also have similar distributions in WISE mid-infrared colours, indicating similar ages of stellar populations and dust levels in the hosts of DDRGs. We conclude that DDRGs and 'normal' RLAGN are hosted by galaxies of the same type, and that DDRG activity is simply a normal part of the life cycle of RLAGN. Restarted jets, particularly for the class of low-excitation radio galaxies, rather than being a product of a particular event in the life of a host galaxy, must instead be caused by smaller scale changes, such as in the accretion system surrounding the black hole.

LOFAR observations of the XMM-LSS field

Astronomy and Astrophysics EDP Sciences (2019)

CL Hale, W Williams, MJ Jarvis, MJ Hardcastle, LK Morabito, TW Shimwell, C Tasse, PN Best, JJ Harwood, I Heywood, I Prandoni, HJA Röttgering, J Sabater, DJB Smith, RJV Weeren

We present observations of the XMM Large-Scale Structure (XMM-LSS) field observed with the LOw Frequency ARray (LOFAR) at 120-168 MHz. Centred at a J2000 declination of $-4.5^{\circ}$, this is a challenging field to observe with LOFAR because of its low elevation with respect to the array. The low elevation of this field reduces the effective collecting area of the telescope, thereby reducing sensitivity. This low elevation also causes the primary beam to be elongated in the north-south direction, which can introduce side lobes in the synthesised beam in this direction. However the XMM-LSS field is a key field to study because of the wealth of ancillary information, encompassing most of the electromagnetic spectrum. The field was observed for a total of 12 hours from three four-hour LOFAR tracks using the Dutch array. The final image presented encompasses $\sim 27$ deg$^2$, which is the region of the observations with a $>$50\% primary beam response. Once combined, the observations reach a central rms of 280 $\mu$Jy beam$^{-1}$ at 144 MHz and have an angular resolution of $7.5 \times \ 8.5$". We present our catalogue of detected sources and investigate how our observations compare to previous radio observations. This includes investigating the flux scale calibration of these observations compared to previous measurements, the implied spectral indices of the sources, the observed source counts and corrections to obtain the true source counts, and finally the clustering of the observed radio sources.

Systematic effects in LOFAR data: A unified calibration strategy


F de Gasperin, TJ Dijkema, A Drabent, M Mevius, D Rafferty, R van Weeren, M Brueggen, JR Callingham, KL Emig, G Heald, HT Intema, LK Morabito, AR Offringa, R Oonk, E Orru, H Rottgering, J Sabater, T Shimwell, A Shulevski, W Williams

LoTSS/HETDEX: Disentangling star formation and AGN activity in gravitationally lensed radio-quiet quasars


HR Stacey, JP McKean, NJ Jackson, PN Best, GC Rivera, JR Callingham, KJ Duncan, G Gurkan, MJ Hardcastle, M Iacobelli, AP Mechev, LK Morabito, I Prandoni, HJA Rottgering, J Sabater, TW Shimwell, C Tasse, WL Williams

A kpc-scale star forming disk surrounding nuclei with shocked outflows (erratum)


E Varenius, JE Conway, I Marti-Vidal, S Aalto, L Barcos-Munoz, S Konig, MA Perez-Torres, AT Deller, J Moldon, JS Gallagher, TM Yoast-Hull, C Horellou, LK Morabito, A Alberdi, N Jackson, R Beswick, TD Carozzi, O Wucknitz, N Ramirez-Olivencia

Revolutionizing Our Understanding of AGN Feedback and its Importance to Galaxy Evolution in the Era of the Next Generation Very Large Array


K Nyland, JJ Harwood, D Mukherjee, P Jagannathan, W Rujopakarn, B Emonts, K Alatalo, GV Bicknell, TA Davis, JE Greene, A Kimball, M Lacy, C Lonsdale, C Lonsdale, WP Maksym, DC Molnar, L Morabito, EJ Murphy, P Patil, I Prandoni, M Sargent, C Vlahakis

LOFAR-Bootes: properties of high- and low-excitation radio galaxies at 0.5 < z < 2.0


WL Williams, GC Rivera, PN Best, MJ Hardcastle, HJA Rottgering, KJ Duncan, F de Gasperin, MJ Jarvis, GK Miley, EK Mahony, LK Morabito, DM Nisbet, I Prandoni, DJB Smith, C Tasse, GJ White

Investigating the cause of the $α\,$-$\,z$ relation

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2018)

LK Morabito, JJ Harwood

The correlation between radio spectral index and redshift has long been used to identify high redshift radio galaxies, but its cause is unknown. Traditional explanations invoke either $(i)$ intrinsic relations between spectral index and power, $(ii)$ environmental differences at high redshift, or $(iii)$ higher inverse Compton losses due to the increased photon energy density of the cosmic microwave background. In this paper we investigate whether the increased inverse Compton losses alone can cause the observed spectral index - redshift correlation by using spectral modelling of nearby radio galaxies to simulate high redshift equivalents. We then apply selection effects and directly compare the simulated radio galaxy sample with an observed sample with sufficient redshift coverage. We find excellent agreement between the two, implying that inverse Compton losses and selection effects alone can largely reproduce the observed spectral index - redshift correlation.

The Far-Infrared Radio Correlation at low radio frequency with LOFAR/H-ATLAS


SC Read, DJB Smith, G Guerkan, MJ Hardcastle, WL Williams, PN Best, E Brinks, G Calistro-Rivera, KT Chyzy, K Duncan, L Dunne, MJ Jarvis, LK Morabito, I Prandoni, HJA Rottgering, J Sabater, S Viaene

LOFAR MSSS: Discovery of a 2.56 Mpc giant radio galaxy associated with a disturbed galaxy group


AO Clarke, G Heald, T Jarrett, JD Bray, MJ Hardcastle, TM Cantwell, AMM Scaife, M Brienza, A Bonafede, RP Breton, W Broderick, D Carbone, JH Croston, JS Farnes, JJ Harwood, V Heesen, A Horneffer, AJ van der Horst, M Iacobelli, W Jurusik, G Kokotanekov, JP McKean, LK Morabito, DD Mulcahy, BS Nikiel-Wroczynski, E Orru, R Paladino, M Pandey-Pommier, M Pietka, R Pizzo, L Pratley, CJ Riseley, HJA Rottgering, A Rowlinson, J Sabater, K Sendlinger, A Shulevski, SS Sridhar, AJ Stewart, C Tasse, S van Velzen, RJ van Weeren, MW Wise

Low-frequency Carbon Radio Recombination Lines. II. The Diffuse Interstellar Medium

The Astrophysical Journal 837 (2017) 142-142

F Salgado, LK Morabito, JBR Oonk, P Salas, MC Toribio, HJA Röttgering, AGGM Tielens

Low-frequency Carbon Radio Recombination Lines. I. Calculations of Departure Coefficients

The Astrophysical Journal 837 (2017) 141-141

F Salgado, LK Morabito, JBR Oonk, P Salas, MC Toribio, HJA Röttgering, AGGM Tielens

Carbon and hydrogen radio recombination lines from the cold clouds towards Cassiopeia A

Monthly Notices of the Royal Astronomical Society 465 (2017) 1066-1088

JBR Oonk, RJ van Weeren, P Salas, F Salgado, LK Morabito, MC Toribio, AGGM Tielens, HJA Röttgering

The CALYMHA survey: Lyα luminosity function and global escape fraction of Lyα photons at z  = 2.23

Monthly Notices of the Royal Astronomical Society 466 (2017) 1242-1258

D Sobral, J Matthee, P Best, A Stroe, H Röttgering, I Oteo, I Smail, L Morabito, A Paulino-Afonso

The LOFAR window on star-forming galaxies and AGNs - curved radio SEDs and IR-radio correlation at 0 < z < 2.5


GC Rivera, WL Williams, MJ Hardcastle, K Duncan, HJA Rottgering, PN Best, M Brueggen, KT Chyzy, CJ Conselice, F de Gasperin, D Engels, G Gurkan, HT Intema, MJ Jarvis, EK Mahony, GK Miley, LK Morabito, I Prandoni, J Sabater, DJB Smith, C Tasse, PP van der Werf, GJ White

Investigating the unification of LOFAR-detected powerful AGN in the Bootes field


LK Morabito, WL Williams, KJ Duncan, HJA Rottgering, G Miley, A Saxena, P Barthel, PN Best, M Bruggen, G Brunetti, KT Chyzy, D Engels, MJ Hardcastle, JJ Harwood, MJ Jarvis, EK Mahony, I Prandoni, TW Shimwell, A Shulevski, C Tasse