JPJahang Prathap
Jahang Prathap
*This is an algorithmically generated author record based on publicly available information.
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Jahang Prathap has a total of 155 co-authors. Here are the top co-authors by number of shared publications:
- Tamal Mukherjee
Macquarie University
10 shared publications - Tayyaba Zafar
School of Mathematical and Physical Sciences, Macquarie University
10 shared publications - Denis Leahy
University of Calgary
6 shared publications - Andrew M. Hopkins
Macquarie University
5 shared publications - Michael J. I. Brown
Monash University
5 shared publications - Stanislav S. Shabala
University of Tasmania
5 shared publications
Latest Publications
- Open Access
- 7 May 2026
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 43
Predicting resolved dust attenuation from local galaxy properties using MaNGA
Accurate spatially resolved dust corrections are critical for interpreting the structure and evolution of star-forming galaxies (SFGs). We present an empirical model for predicting spatially resolved dust attenuation ( $A_V$ ) in SFGs using integral field spectroscopy from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. Using a sample of 5 155 galaxies over $7.20 \lt M_*\lt 11.14$ and $0.0002 \lt z \lt 0.1444$ , we derive $A_V$ maps from the Balmer decrement across more than 1 898 954 star-forming spaxels. Using local star formation rate surface density ( $\Sigma_{\text{SFR}}$ ) as a predictor, the model achieves $R^2 = 0.69$ and RMSE $=0.22$ mag, with residuals that are approximately Gaussian and centred near zero. It predicts $A_V$ within a factor of $\sim$ 1.3 on kpc scales. We also demonstrate that the relation can be applied iteratively to recover dust–corrected $\Sigma_{\mathrm{SFR}}$ from uncorrected values, converging by the fourth iteration with minimal residual bias ( $-0.01$ mag) and low RMSE ( $0.42$ mag). The model accurately reproduces $A_V$ maps across diverse morphologies and orientations, including edge-on systems. It also recovers the observed radial $A_V$ profiles, capturing their dependence on stellar mass and relative star formation activity, with more massive and more strongly star-forming galaxies showing steeper gradients.- 7 May 2026
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 43
Open AccessPredicting resolved dust attenuation from local galaxy properties using MaNGA
Accurate spatially resolved dust corrections are critical for interpreting the structure and evolution of star-forming galaxies (SFGs). We present an empirical model for predicting spatially resolved dust attenuation ( $A_V$ ) in SFGs using integral field spectroscopy from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. Using a sample of 5 155 galaxies over $7.20 \lt M_*\lt 11.14$ and $0.0002 \lt z \lt 0.1444$ , we derive $A_V$ maps from the Balmer decrement across more than 1 898 954 star-forming spaxels. Using local star formation rate surface density ( $\Sigma_{\text{SFR}}$ ) as a predictor, the model achieves $R^2 = 0.69$ and RMSE $=0.22$ mag, with residuals that are approximately Gaussian and centred near zero. It predicts $A_V$ within a factor of $\sim$ 1.3 on kpc scales. We also demonstrate that the relation can be applied iteratively to recover dust–corrected $\Sigma_{\mathrm{SFR}}$ from uncorrected values, converging by the fourth iteration with minimal residual bias ( $-0.01$ mag) and low RMSE ( $0.42$ mag). The model accurately reproduces $A_V$ maps across diverse morphologies and orientations, including edge-on systems. It also recovers the observed radial $A_V$ profiles, capturing their dependence on stellar mass and relative star formation activity, with more massive and more strongly star-forming galaxies showing steeper gradients. - Open Access
- 27 March 2026
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 43, 1-15
EMU/GAMA: Refining dust extinction corrections for Hα luminosity functions using radio-based calibration
We present a novel approach to correcting H ${\unicode{x03B1}}$ luminosity functions for dust extinction by calibrating against radio-based star formation rates (SFRs), using data from the Evolutionary Map of the Universe (EMU) and Galaxy and Mass Assembly (GAMA) surveys. Accurate dust correction is essential for deriving SFRs from rest-frame UV-optical emission lines, particularly as the James Webb Space Telescope extends such measurements to galaxies at $z\gt5$ . While a luminosity dependence of dust obscuration has long been recognised, our method exploits the empirical relationship between obscured (H ${\unicode{x03B1}}$ ) and unobscured (radio) SFRs to provide a dust correction that can be applied where traditional spectroscopic techniques, for example, Balmer line based approaches, are unavailable. We apply the SFR based dust correction to 25 published H ${\unicode{x03B1}}$ luminosity functions spanning $0\lt z\lt 8$ and derive corresponding star formation rate densities (SFRDs). Adopting the locally calibrated H ${\unicode{x03B1}}$ –radio relation ends up with an overestimate of the cosmic SFRD by more than two orders of magnitude at $z\gtrsim1$ . Motivated by the luminosity dependent relation in the local Universe, we introduce a new model where the luminosity dependence of the dust obscuration decreases with increasing redshift. This approach can reproduce observed SFRDs across cosmic time. These results highlight the potential of a radio-based calibration for dust correction, where a luminosity dependent correction would need to decline in strength with increasing redshift. This implies that the dust content or distribution in galaxies at early epochs differs substantially from that in the local Universe.- 27 March 2026
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 43, 1-15
Open AccessEMU/GAMA: Refining dust extinction corrections for Hα luminosity functions using radio-based calibration
We present a novel approach to correcting H ${\unicode{x03B1}}$ luminosity functions for dust extinction by calibrating against radio-based star formation rates (SFRs), using data from the Evolutionary Map of the Universe (EMU) and Galaxy and Mass Assembly (GAMA) surveys. Accurate dust correction is essential for deriving SFRs from rest-frame UV-optical emission lines, particularly as the James Webb Space Telescope extends such measurements to galaxies at $z\gt5$ . While a luminosity dependence of dust obscuration has long been recognised, our method exploits the empirical relationship between obscured (H ${\unicode{x03B1}}$ ) and unobscured (radio) SFRs to provide a dust correction that can be applied where traditional spectroscopic techniques, for example, Balmer line based approaches, are unavailable. We apply the SFR based dust correction to 25 published H ${\unicode{x03B1}}$ luminosity functions spanning $0\lt z\lt 8$ and derive corresponding star formation rate densities (SFRDs). Adopting the locally calibrated H ${\unicode{x03B1}}$ –radio relation ends up with an overestimate of the cosmic SFRD by more than two orders of magnitude at $z\gtrsim1$ . Motivated by the luminosity dependent relation in the local Universe, we introduce a new model where the luminosity dependence of the dust obscuration decreases with increasing redshift. This approach can reproduce observed SFRDs across cosmic time. These results highlight the potential of a radio-based calibration for dust correction, where a luminosity dependent correction would need to decline in strength with increasing redshift. This implies that the dust content or distribution in galaxies at early epochs differs substantially from that in the local Universe. - Open Access
- 25 March 2026
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 43, 1-19
EMU/GAMA: A statistical perspective on active galactic nuclei diagnostics
While it is well known that galaxies are composites of many emission processes, quantifying the various contributions remains challenging. In this work, we use unsupervised machine learning based clustering algorithms to evaluate the agreement between the clustering tools and astrophysical classifications, and hence quantify the fractional contributions of star formation processes and nuclear black hole activity to the total galaxy energy budget of radio sources. We perform clustering on the multiwavelength (optical, infrared (IR), and radio) active galactic nuclei (AGN) diagnostic spaces, using the data from the G09 and G23 fields from the Galaxy and Mass Assembly (GAMA) survey, Evolutionary Map of the Universe (EMU) survey, and the Wide-field Infrared Survey Explorer. We find that the statistical clustering recovers $\approx$ 90% of the star forming galaxies (SFGs) and $\approx$ 80% of the AGN. We define a new IR-radio AGN diagnostic scheme that identifies radio AGN from IR SFGs and AGN, corresponding to the KMeans cluster with approximately 90% reliability. We demonstrate the superior power of radio AGN selection in higher dimensions using a three-dimensional space composed of directly observable parameters ( ${W_1-W_2}$ colour, ${W_2}$ magnitude, and the 1.4 GHz radio flux density). This novel three dimensional diagnostic shows immense potential in radio AGN selection that is close to 90% reliable and 90% complete. We also publish a catalogue of radio sources in the EMU survey with associated probabilities for them to be active in the optical regime, through which we emphasise the philosophy of considering a galaxy to be composed of various fractions rather than a binary classification of SFGs and AGN.- 25 March 2026
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 43, 1-19
Open AccessEMU/GAMA: A statistical perspective on active galactic nuclei diagnostics
While it is well known that galaxies are composites of many emission processes, quantifying the various contributions remains challenging. In this work, we use unsupervised machine learning based clustering algorithms to evaluate the agreement between the clustering tools and astrophysical classifications, and hence quantify the fractional contributions of star formation processes and nuclear black hole activity to the total galaxy energy budget of radio sources. We perform clustering on the multiwavelength (optical, infrared (IR), and radio) active galactic nuclei (AGN) diagnostic spaces, using the data from the G09 and G23 fields from the Galaxy and Mass Assembly (GAMA) survey, Evolutionary Map of the Universe (EMU) survey, and the Wide-field Infrared Survey Explorer. We find that the statistical clustering recovers $\approx$ 90% of the star forming galaxies (SFGs) and $\approx$ 80% of the AGN. We define a new IR-radio AGN diagnostic scheme that identifies radio AGN from IR SFGs and AGN, corresponding to the KMeans cluster with approximately 90% reliability. We demonstrate the superior power of radio AGN selection in higher dimensions using a three-dimensional space composed of directly observable parameters ( ${W_1-W_2}$ colour, ${W_2}$ magnitude, and the 1.4 GHz radio flux density). This novel three dimensional diagnostic shows immense potential in radio AGN selection that is close to 90% reliable and 90% complete. We also publish a catalogue of radio sources in the EMU survey with associated probabilities for them to be active in the optical regime, through which we emphasise the philosophy of considering a galaxy to be composed of various fractions rather than a binary classification of SFGs and AGN. - Open Access
- 19 January 2026
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 43, 1-23
A census of double-peaked Lyman-α emitters in MAGPI: Classification, global characteristics, and spatially resolved properties
Double-peaked Lyman- $\alpha$ (Ly $\alpha$ ) profiles provide critical insights into gas kinematics and the distribution of neutral hydrogen (H i) from the interstellar to the intergalactic medium (ISM to IGM) and serve as valuable diagnostics of ionising Lyman continuum (LyC) photon escape. We present a study of the global and spatially resolved properties of double-peaked Ly $\alpha$ emitters (LAEs), based on VLT/MUSE data from the Middle Ages Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey. From a parent sample of 417 LAEs at $z = 2.9 - 6.6$ in the first 35 fields, we identify 108 double-peaked LAEs using an automated peak classification technique. We measure a double-peak fraction of $\sim$ 37% at $z \lt 4$ , decreasing to $\sim$ 14% at $z \gt 4$ , likely due to enhanced IGM attenuation. Approximately 17% of the double-peaked LAEs are blue-dominated, possibly tracing gas inflows, though backscattering remains a viable alternative for sources without systemic redshift. The blue-to-total flux ratio exhibits a luminosity dependence: fainter lines generally show higher blue flux, though a few luminous sources also show strong blue peaks. We find a significant narrowing of the red peak at $z\gt4$ , despite the presence of the blue peak, indicating intrinsic galaxy evolution rather than an effect of IGM attenuation. Several LAEs exhibit residual flux in the absorption trough, with normalised trough flux anticorrelating with peak separation, reflecting variations in H i column density. We further investigate spatially resolved properties of ten red-dominated LAEs with extended Ly $\alpha$ halos. Despite azimuthal variations, both the blue-to-total flux ratio and normalised trough flux density increase with radius, while peak separation decreases. The red peak asymmetry shows only minor radial changes. These trends are consistent with variations in shell outflow velocity and H i column density across the halos. However, some exceptions to these patterns are also noted. Based on peak separation, red peak asymmetry, and residual trough flux, we identify five LAEs as strong LyC leaker candidates.- 19 January 2026
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 43, 1-23
Open AccessA census of double-peaked Lyman-α emitters in MAGPI: Classification, global characteristics, and spatially resolved properties
Double-peaked Lyman- $\alpha$ (Ly $\alpha$ ) profiles provide critical insights into gas kinematics and the distribution of neutral hydrogen (H i) from the interstellar to the intergalactic medium (ISM to IGM) and serve as valuable diagnostics of ionising Lyman continuum (LyC) photon escape. We present a study of the global and spatially resolved properties of double-peaked Ly $\alpha$ emitters (LAEs), based on VLT/MUSE data from the Middle Ages Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey. From a parent sample of 417 LAEs at $z = 2.9 - 6.6$ in the first 35 fields, we identify 108 double-peaked LAEs using an automated peak classification technique. We measure a double-peak fraction of $\sim$ 37% at $z \lt 4$ , decreasing to $\sim$ 14% at $z \gt 4$ , likely due to enhanced IGM attenuation. Approximately 17% of the double-peaked LAEs are blue-dominated, possibly tracing gas inflows, though backscattering remains a viable alternative for sources without systemic redshift. The blue-to-total flux ratio exhibits a luminosity dependence: fainter lines generally show higher blue flux, though a few luminous sources also show strong blue peaks. We find a significant narrowing of the red peak at $z\gt4$ , despite the presence of the blue peak, indicating intrinsic galaxy evolution rather than an effect of IGM attenuation. Several LAEs exhibit residual flux in the absorption trough, with normalised trough flux anticorrelating with peak separation, reflecting variations in H i column density. We further investigate spatially resolved properties of ten red-dominated LAEs with extended Ly $\alpha$ halos. Despite azimuthal variations, both the blue-to-total flux ratio and normalised trough flux density increase with radius, while peak separation decreases. The red peak asymmetry shows only minor radial changes. These trends are consistent with variations in shell outflow velocity and H i column density across the halos. However, some exceptions to these patterns are also noted. Based on peak separation, red peak asymmetry, and residual trough flux, we identify five LAEs as strong LyC leaker candidates. - Open Access
A Census of Double-Peaked Lyman-alpha Emitters in MAGPI: Classification, Global Characteristics, and Spatially Resolved Properties
Double-peaked Lyman-$\alpha$ (Ly$\alpha$) profiles provide critical insights into gas kinematics and the distribution of neutral hydrogen (HI) from the interstellar to the intergalactic medium (ISM to IGM), and serve as valuable diagnostics of ionising Lyman continuum (LyC) photon escape. We present a study of the global and spatially resolved properties of double-peaked Ly$\alpha$ emitters (LAEs) based on VLT/MUSE data from the MAGPI survey. From a parent sample of 417 LAEs at z = 2.9 - 6.6 in the first 35 fields, we identify 108 double-peaked LAEs using an automated peak classification technique. We measure a double-peak fraction of $\sim37\%$ at $z < 4$, decreasing to $\sim14\%$ at $z > 4$, likely due to enhanced IGM attenuation. Approximately $17\%$ of the double-peaked LAEs are blue-dominated, suggesting gas inflows. The blue-to-total flux ratio exhibits a luminosity dependence: fainter lines generally show higher blue flux, though some luminous sources also show strong blue peaks. We find a narrowing of the red peak at $z > 4$, despite the presence of the blue peak, indicating intrinsic galaxy evolution rather than IGM attenuation. Several LAEs exhibit residual flux in the absorption trough, with normalised trough flux anticorrelating with peak separation, reflecting variations in HI column density. We further investigate spatially resolved properties of ten red-dominated LAEs with extended Ly$\alpha$ halos. Despite azimuthal variations, both the blue-to-total flux ratio and normalised trough flux density increase with radius, while peak separation decreases. The red peak asymmetry shows only minor radial changes. These trends are consistent with variations in shell outflow velocity and HI column density across the halos. Based on peak separation, red peak asymmetry, and residual trough flux, we identify five LAEs as strong LyC-leaker candidates.Open AccessA Census of Double-Peaked Lyman-alpha Emitters in MAGPI: Classification, Global Characteristics, and Spatially Resolved Properties
Double-peaked Lyman-$\alpha$ (Ly$\alpha$) profiles provide critical insights into gas kinematics and the distribution of neutral hydrogen (HI) from the interstellar to the intergalactic medium (ISM to IGM), and serve as valuable diagnostics of ionising Lyman continuum (LyC) photon escape. We present a study of the global and spatially resolved properties of double-peaked Ly$\alpha$ emitters (LAEs) based on VLT/MUSE data from the MAGPI survey. From a parent sample of 417 LAEs at z = 2.9 - 6.6 in the first 35 fields, we identify 108 double-peaked LAEs using an automated peak classification technique. We measure a double-peak fraction of $\sim37\%$ at $z < 4$, decreasing to $\sim14\%$ at $z > 4$, likely due to enhanced IGM attenuation. Approximately $17\%$ of the double-peaked LAEs are blue-dominated, suggesting gas inflows. The blue-to-total flux ratio exhibits a luminosity dependence: fainter lines generally show higher blue flux, though some luminous sources also show strong blue peaks. We find a narrowing of the red peak at $z > 4$, despite the presence of the blue peak, indicating intrinsic galaxy evolution rather than IGM attenuation. Several LAEs exhibit residual flux in the absorption trough, with normalised trough flux anticorrelating with peak separation, reflecting variations in HI column density. We further investigate spatially resolved properties of ten red-dominated LAEs with extended Ly$\alpha$ halos. Despite azimuthal variations, both the blue-to-total flux ratio and normalised trough flux density increase with radius, while peak separation decreases. The red peak asymmetry shows only minor radial changes. These trends are consistent with variations in shell outflow velocity and HI column density across the halos. Based on peak separation, red peak asymmetry, and residual trough flux, we identify five LAEs as strong LyC-leaker candidates. - Open Access
- 2 June 2025
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 42, 1-17
EMU/GAMA: A new approach to characterising radio luminosity functions
This study characterises the radio luminosity functions (RLFs) for star forming galaxies (SFGs) and active galactic nuclei (AGN) using statistical redshift estimation in the absence of comprehensive spectroscopic data. Sensitive radio surveys over large areas detect many sources with faint optical and infrared counterparts, for which redshifts and spectra are unavailable. This challenges our attempt to understand the population of radio sources. Statistical tools are often used to model parameters (such as redshift) as an alternative to observational data. Using the data from GAMA G23 and EMU early science observations, we explore simple statistical techniques to estimate the redshifts in order to measure the RLFs of the G23 radio sources as a whole and for SFGs and AGN separately. Redshifts and AGN/SFG classifications are assigned statistically for those radio sources without spectroscopic data. The calculated RLFs are compared with existing studies, and the results suggest that the RLFs match remarkably well for low redshift galaxies with an optical counterpart. We use a more realistic high redshift distribution to model the redshifts of (most likely) high redshift radio sources and find that the LFs from our approach match well with measured LFs. We also look at strategies to compare the RLFs of radio sources without an optical counterpart to existing studies.
- 2 June 2025
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 42, 1-17
Open AccessEMU/GAMA: A new approach to characterising radio luminosity functions
This study characterises the radio luminosity functions (RLFs) for star forming galaxies (SFGs) and active galactic nuclei (AGN) using statistical redshift estimation in the absence of comprehensive spectroscopic data. Sensitive radio surveys over large areas detect many sources with faint optical and infrared counterparts, for which redshifts and spectra are unavailable. This challenges our attempt to understand the population of radio sources. Statistical tools are often used to model parameters (such as redshift) as an alternative to observational data. Using the data from GAMA G23 and EMU early science observations, we explore simple statistical techniques to estimate the redshifts in order to measure the RLFs of the G23 radio sources as a whole and for SFGs and AGN separately. Redshifts and AGN/SFG classifications are assigned statistically for those radio sources without spectroscopic data. The calculated RLFs are compared with existing studies, and the results suggest that the RLFs match remarkably well for low redshift galaxies with an optical counterpart. We use a more realistic high redshift distribution to model the redshifts of (most likely) high redshift radio sources and find that the LFs from our approach match well with measured LFs. We also look at strategies to compare the RLFs of radio sources without an optical counterpart to existing studies.
- Top Cited PapersOpen Access
- 27 May 2025
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 42, 1-32
The Evolutionary Map of the Universe: A new radio atlas for the southern hemisphere sky
We present the Evolutionary Map of the Universe (EMU) survey conducted with the Australian Square Kilometre Array Pathfinder (ASKAP). EMU aims to deliver the touchstone radio atlas of the southern hemisphere. We introduce EMU and review its science drivers and key science goals, updated and tailored to the current ASKAP five-year survey plan. The development of the survey strategy and planned sky coverage is presented, along with the operational aspects of the survey and associated data analysis, together with a selection of diagnostics demonstrating the imaging quality and data characteristics. We give a general description of the value-added data pipeline and data products before concluding with a discussion of links to other surveys and projects and an outline of EMU’s legacy value.
- 27 May 2025
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 42, 1-32
Top Cited PapersOpen AccessThe Evolutionary Map of the Universe: A new radio atlas for the southern hemisphere sky
We present the Evolutionary Map of the Universe (EMU) survey conducted with the Australian Square Kilometre Array Pathfinder (ASKAP). EMU aims to deliver the touchstone radio atlas of the southern hemisphere. We introduce EMU and review its science drivers and key science goals, updated and tailored to the current ASKAP five-year survey plan. The development of the survey strategy and planned sky coverage is presented, along with the operational aspects of the survey and associated data analysis, together with a selection of diagnostics demonstrating the imaging quality and data characteristics. We give a general description of the value-added data pipeline and data products before concluding with a discussion of links to other surveys and projects and an outline of EMU’s legacy value.
- Open Access
EMU/GAMA: A new approach to characterising radio luminosity functions
This study characterises the radio luminosity functions (RLFs) for SFGs and AGN using statistical redshift estimation in the absence of comprehensive spectroscopic data. Sensitive radio surveys over large areas detect many sources with faint optical and infrared counterparts, for which redshifts and spectra are unavailable. This challenges our attempt to understand the population of radio sources. Statistical tools are often used to model parameters (such as redshift) as an alternative to observational data. Using the data from GAMA G23 and EMU early science observations, we explore simple statistical techniques to estimate the redshifts in order to measure the RLFs of the G23 radio sources as a whole and for SFGs and AGN separately. Redshifts and AGN/SFG classifications are assigned statistically for those radio sources without spectroscopic data. The calculated RLFs are compared with existing studies, and the results suggest that the RLFs match remarkably well for low redshift galaxies with an optical counterpart. We use a more realistic high redshift distribution to model the redshifts of (most likely) high redshift radio sources and find that the LFs from our approach match well with measured LFs. We also look at strategies to compare the RLFs of radio sources without an optical counterpart to existing studies.
Open AccessEMU/GAMA: A new approach to characterising radio luminosity functions
This study characterises the radio luminosity functions (RLFs) for SFGs and AGN using statistical redshift estimation in the absence of comprehensive spectroscopic data. Sensitive radio surveys over large areas detect many sources with faint optical and infrared counterparts, for which redshifts and spectra are unavailable. This challenges our attempt to understand the population of radio sources. Statistical tools are often used to model parameters (such as redshift) as an alternative to observational data. Using the data from GAMA G23 and EMU early science observations, we explore simple statistical techniques to estimate the redshifts in order to measure the RLFs of the G23 radio sources as a whole and for SFGs and AGN separately. Redshifts and AGN/SFG classifications are assigned statistically for those radio sources without spectroscopic data. The calculated RLFs are compared with existing studies, and the results suggest that the RLFs match remarkably well for low redshift galaxies with an optical counterpart. We use a more realistic high redshift distribution to model the redshifts of (most likely) high redshift radio sources and find that the LFs from our approach match well with measured LFs. We also look at strategies to compare the RLFs of radio sources without an optical counterpart to existing studies.
- Open Access
- 11 December 2024
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 41
The MAGPI Survey: Insights into the Lyα line widths and the size of ionised bubbles at the edge of cosmic reionisation
We present spectroscopic properties of 22 Ly $\alpha$ emitters (LAEs) at $z = 5.5 - 6.6$ with Ly $\alpha$ luminosity $\mathrm{log}( L_{\mathrm{Ly}\alpha} \, [\mathrm{erg} \, \mathrm{s}^{-1}]) = 42.4 - 43.5 $ , obtained using VLT/MUSE as part of the Middle Ages Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey. Additionally, we incorporate broad-band photometric data from the Subaru Hyper Suprime-Cam (HSC) Wide layer for 17 LAEs in our sample. The HSC-y band magnitudes show that our LAEs are UV-bright, with rest-frame absolute UV magnitudes $ -19.74 \leq \mathrm{M}_{\mathrm{UV}} \leq -23.27$ . We find that the Ly $\alpha$ line width increases with Ly $\alpha$ luminosity, and this trend becomes more prominent at $z \gt 6$ where Ly $\alpha$ lines become significantly broadened ( $\gtrsim+260 \, \mathrm{km}\, \mathrm{s}^{-1}$ ) at luminosities $\mathrm{log}( L_{\mathrm{Ly}\alpha} \, [\mathrm{erg} \, \mathrm{s}^{-1}]) \gt 43 $ . This broadening is consistent with previous studies, suggesting that these sources are located inside larger ionised bubbles. We observe a slightly elevated ionising photon production efficiency estimated for LAEs at $z \gt 6$ , which indicates that younger galaxies could be producing more ionising photons per UV luminosity. A tentative anti-correlation between ionising photon production efficiency and Ly $\alpha$ rest-frame equivalent width is noticed, which could indicate a time delay between production and escape of ionising photon primarily due to supernovae activity. Furthermore, we find a positive correlation between radius of ionised regions and Ly $\alpha$ line width, which again suggests that large ionised bubbles are created around these LAEs, which are allowing them to self-shield from the scattering effects of the intergalactic medium (IGM). We also detect two very closely separated LAEs at $z = 6.046$ (projected spatial distance between the cores is 15.92 kpc). This is the LAE pair with the smallest separation ever discovered in the reionisation epoch. The size of their respective bubbles suggests that they likely sit inside a common large ionised region. Such a closely separated LAE pair increases the size of ionised bubble, potentially allowing a boosted transmission of Ly $\alpha$ through neutral IGM and also supports an accelerated reionisation scenario.- 11 December 2024
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 41
Open AccessThe MAGPI Survey: Insights into the Lyα line widths and the size of ionised bubbles at the edge of cosmic reionisation
We present spectroscopic properties of 22 Ly $\alpha$ emitters (LAEs) at $z = 5.5 - 6.6$ with Ly $\alpha$ luminosity $\mathrm{log}( L_{\mathrm{Ly}\alpha} \, [\mathrm{erg} \, \mathrm{s}^{-1}]) = 42.4 - 43.5 $ , obtained using VLT/MUSE as part of the Middle Ages Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey. Additionally, we incorporate broad-band photometric data from the Subaru Hyper Suprime-Cam (HSC) Wide layer for 17 LAEs in our sample. The HSC-y band magnitudes show that our LAEs are UV-bright, with rest-frame absolute UV magnitudes $ -19.74 \leq \mathrm{M}_{\mathrm{UV}} \leq -23.27$ . We find that the Ly $\alpha$ line width increases with Ly $\alpha$ luminosity, and this trend becomes more prominent at $z \gt 6$ where Ly $\alpha$ lines become significantly broadened ( $\gtrsim+260 \, \mathrm{km}\, \mathrm{s}^{-1}$ ) at luminosities $\mathrm{log}( L_{\mathrm{Ly}\alpha} \, [\mathrm{erg} \, \mathrm{s}^{-1}]) \gt 43 $ . This broadening is consistent with previous studies, suggesting that these sources are located inside larger ionised bubbles. We observe a slightly elevated ionising photon production efficiency estimated for LAEs at $z \gt 6$ , which indicates that younger galaxies could be producing more ionising photons per UV luminosity. A tentative anti-correlation between ionising photon production efficiency and Ly $\alpha$ rest-frame equivalent width is noticed, which could indicate a time delay between production and escape of ionising photon primarily due to supernovae activity. Furthermore, we find a positive correlation between radius of ionised regions and Ly $\alpha$ line width, which again suggests that large ionised bubbles are created around these LAEs, which are allowing them to self-shield from the scattering effects of the intergalactic medium (IGM). We also detect two very closely separated LAEs at $z = 6.046$ (projected spatial distance between the cores is 15.92 kpc). This is the LAE pair with the smallest separation ever discovered in the reionisation epoch. The size of their respective bubbles suggests that they likely sit inside a common large ionised region. Such a closely separated LAE pair increases the size of ionised bubble, potentially allowing a boosted transmission of Ly $\alpha$ through neutral IGM and also supports an accelerated reionisation scenario. - Open Access
- 21 February 2024
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 41, 1-16
EMU/GAMA: A technique for detecting active galactic nuclei in low mass systems
We propose a new method for identifying active galactic nuclei (AGN) in low mass ( $\mathrm{M}_*\leq10^{10}\mathrm{M}_\odot$ ) galaxies. This method relies on spectral energy distribution (SED) fitting to identify galaxies whose radio flux density has an excess over that expected from star formation alone. Combining data in the Galaxy and Mass Assembly (GAMA) G23 region from GAMA, Evolutionary Map of the Universe (EMU) early science observations, and Wide-field Infrared Survey Explorer (WISE), we compare this technique with a selection of different AGN diagnostics to explore the similarities and differences in AGN classification. We find that diagnostics based on optical and near-infrared criteria (the standard BPT diagram, the WISE colour criterion, and the mass-excitation, or MEx diagram) tend to favour detection of AGN in high mass, high luminosity systems, while the “ProSpect” SED fitting tool can identify AGN efficiently in low mass systems. We investigate an explanation for this result in the context of proportionally lower mass black holes in lower mass galaxies compared to higher mass galaxies and differing proportions of emission from AGN and star formation dominating the light at optical and infrared wavelengths as a function of galaxy stellar mass. We conclude that SED-derived AGN classification is an efficient approach to identify low mass hosts with low radio luminosity AGN.- 21 February 2024
- Published by Cambridge University Press (CUP) in Publications of the Astronomical Society of Australia
- Vol. 41, 1-16
Open AccessEMU/GAMA: A technique for detecting active galactic nuclei in low mass systems
We propose a new method for identifying active galactic nuclei (AGN) in low mass ( $\mathrm{M}_*\leq10^{10}\mathrm{M}_\odot$ ) galaxies. This method relies on spectral energy distribution (SED) fitting to identify galaxies whose radio flux density has an excess over that expected from star formation alone. Combining data in the Galaxy and Mass Assembly (GAMA) G23 region from GAMA, Evolutionary Map of the Universe (EMU) early science observations, and Wide-field Infrared Survey Explorer (WISE), we compare this technique with a selection of different AGN diagnostics to explore the similarities and differences in AGN classification. We find that diagnostics based on optical and near-infrared criteria (the standard BPT diagram, the WISE colour criterion, and the mass-excitation, or MEx diagram) tend to favour detection of AGN in high mass, high luminosity systems, while the “ProSpect” SED fitting tool can identify AGN efficiently in low mass systems. We investigate an explanation for this result in the context of proportionally lower mass black holes in lower mass galaxies compared to higher mass galaxies and differing proportions of emission from AGN and star formation dominating the light at optical and infrared wavelengths as a function of galaxy stellar mass. We conclude that SED-derived AGN classification is an efficient approach to identify low mass hosts with low radio luminosity AGN.