Publications


Cross-correlating radio continuum surveys and CMB lensing: constraining redshift distributions, galaxy bias and cosmology

Monthly Notices of the Royal Astronomical Society Oxford University Press (2021) stab046

D Alonso, M Jarvis, E Bellini

We measure the harmonic-space auto-power spectrum of the galaxy overdensity in the LOFAR Two-metre Sky Survey (LoTSS) First Data Release and its cross correlation with the map of the lensing convergence of the cosmic microwave background (CMB) from the Planck collaboration. We report a ∼5σ detection of the cross-correlation. We show that the combination of the clustering power spectrum and CMB lensing cross-correlation allows us to place constraints on the high-redshift tail of the redshift distribution, one of the largest sources of uncertainty in the use of continuum surveys for cosmology. Our analysis shows a preference for a broader redshift tail than that predicted by the photometric redshifts contained in the LoTSS value added catalog, as expected, and more compatible with predictions from simulations and spectroscopic data. Although the ability of CMB lensing to constrain the width and tail of the redshift distribution could also be valuable for the analysis of current and future photometric weak lensing surveys, we show that its performance relies strongly on the redshift evolution of the galaxy bias. Assuming the redshift distribution predicted by the Square Kilometre Array Design simulations, we use our measurements to place constraints on the linear bias of radio galaxies and the amplitude of matter inhomogeneities σ8, finding σ8=0.69+0.14−0.21 assuming the galaxy bias scales with the inverse of the linear growth factor, and σ8=0.79+0.17−0.32 assuming a constant bias.


The Evolution of Gas-Phase Metallicity and Resolved Abundances in Star-forming Galaxies at z ≈ 0.6 – 1.8

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2020)

S Gillman, A Tiley, A Swinbank, U Dudzevičiūtė, R Sharples, I Smail, C Harrison, AJ Bunker, M Bureau, M Cirasuolo, GE Magdis, T Mendel, JP Stott

<jats:title>Abstract</jats:title> <jats:p>We present an analysis of the chemical abundance properties of ≈650 star-forming galaxies at z ≈ 0.6 – 1.8. Using integral-field observations from the K - band Multi-Object Spectrograph (KMOS), we quantify the [N ii]/Hα emission-line ratio, a proxy for the gas-phase Oxygen abundance within the interstellar medium. We define the stellar mass – metallicity relation at z ≈ 0.6 – 1.0 and z ≈ 1.2 – 1.8 and analyse the correlation between the scatter in the relation and fundamental galaxy properties (e.g. Hα star-formation rate, Hα specific star-formation rate, rotation dominance, stellar continuum half-light radius and Hubble-type morphology). We find that for a given stellar mass, more highly star-forming, larger and irregular galaxies have lower gas-phase metallicities, which may be attributable to their lower surface mass densities and the higher gas fractions of irregular systems. We measure the radial dependence of gas-phase metallicity in the galaxies, establishing a median, beam smearing-corrected, metallicity gradient of ΔZ/ΔR= 0.002 ± 0.004 dex kpc−1, indicating on average there is no significant dependence on radius. The metallicity gradient of a galaxy is independent of its rest-frame optical morphology, whilst correlating with its stellar mass and specific star-formation rate, in agreement with an inside-out model of galaxy evolution, as well as its rotation dominance. We quantify the evolution of metallicity gradients, comparing the distribution of ΔZ/ΔR in our sample with numerical simulations and observations at z ≈ 0 – 3. Galaxies in our sample exhibit flatter metallicity gradients than local star-forming galaxies, in agreement with numerical models in which stellar feedback plays a crucial role redistributing metals.</jats:p>


WISDOM project – VI. Exploring the relation between supermassive black hole mass and galaxy rotation with molecular gas

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 500 (2020) 1933-1952

MD Smith, M Bureau, TA Davis, M Cappellari, L Liu, K Onishi, S Iguchi, EV North, M Sarzi

<jats:title>ABSTRACT</jats:title> <jats:p>Empirical correlations between the masses of supermassive black holes (SMBHs) and properties of their host galaxies are well established. Among these is the correlation with the flat rotation velocity of each galaxy measured either at a large radius in its rotation curve or via a spatially integrated emission-line width. We propose here the use of the deprojected integrated CO emission-line width as an alternative tracer of this rotation velocity, which has already been shown useful for the Tully–Fisher (luminosity–rotation velocity) relation. We investigate the correlation between CO line widths and SMBH masses for two samples of galaxies with dynamical SMBH mass measurements, with spatially resolved and unresolved CO observations, respectively. The tightest correlation is found using the resolved sample of 25 galaxies as $\log (M_\mathrm{BH}/\mathrm{M_\odot })=(7.5\pm 0.1)+(8.5\pm 0.9)[\log (W_\mathrm{50}/\sin i \, \mathrm{km\, s}^{-1})-2.7]$, where MBH is the central SMBH mass, W50 is the full width at half-maximum of a double-horned emission-line profile, and i is the inclination of the CO disc. This relation has a total scatter of $0.6\,$ dex, comparable to those of other SMBH mass correlations, and dominated by the intrinsic scatter of $0.5\,$ dex. A tight correlation is also found between the deprojected CO line widths and the stellar velocity dispersions averaged within one effective radius. We apply our correlation to the COLD GASS sample to estimate the local SMBH mass function.</jats:p>


SDSS-IV MaNGA: the indispensable role of bars in enhancing the central star formation of low-z galaxies

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2020)

L Lin, C Li, C Du, E Wang, T Xiao, M Bureau, A Fraser-McKelvie, K Masters, L Lin, D Wake, L Hao

&lt;jats:title&gt;Abstract&lt;/jats:title&gt; &lt;jats:p&gt;We analyse two-dimensional maps and radial profiles of EW(H&#x3B1;), EW(H&#x3B4;A), and Dn(4000) of low-redshift galaxies using integral field spectroscopy from the MaNGA survey. Out of &#x2248;1400 nearly face-on late-type galaxies with a redshift z &amp;amp;lt; 0.05, we identify 121 &#x201C;turnover&#x201D; galaxies that each have a central upturn in EW(H&#x3B1;), EW(H&#x3B4;A) and/or a central drop in Dn(4000), indicative of ongoing/recent star formation. The turnover features are found mostly in galaxies with a stellar mass above &#x223C;1010 M&#x2299; and NUV-r colour less than &#x2248;5. The majority of the turnover galaxies are barred, with a bar fraction of 89&#xB1;3%. Furthermore, for barred galaxies the radius of the central turnover region is found to tightly correlate with one third of the bar length. Comparing the observed and the inward extrapolated star formation rate surface density, we estimate that the central SFR have been enhanced by an order of magnitude. Conversely, only half of the barred galaxies in our sample have a central turnover feature, implying that the presence of a bar is not sufficient to lead to a central SF enhancement. We further examined the SF enhancement in paired galaxies, as well as the local environment, finding no relation. This implies that environment is not a driving factor for central SF enhancement in our sample. Our results reinforce both previous findings and theoretical expectation that galactic bars play a crucial role in the secular evolution of galaxies by driving gas inflow and enhancing the star formation and bulge growth in the center.&lt;/jats:p&gt;


Augmenting machine learning photometric redshifts with Gaussian mixture models

Monthly Notices of the Royal Astronomical Society Oxford University Press 498 (2020) 5498-5510

PW Hatfield, IA Almosallam, MJ Jarvis, N Adams, RAA Bowler, Z Gomes, SJ Roberts, C Schreiber

Wide-area imaging surveys are one of the key ways of advancing our understanding of cosmology, galaxy formation physics, and the large-scale structure of the Universe in the coming years. These surveys typically require calculating redshifts for huge numbers (hundreds of millions to billions) of galaxies – almost all of which must be derived from photometry rather than spectroscopy. In this paper, we investigate how using statistical models to understand the populations that make up the colour–magnitude distribution of galaxies can be combined with machine learning photometric redshift codes to improve redshift estimates. In particular, we combine the use of Gaussian mixture models with the high-performing machine-learning photo-z algorithm GPz and show that modelling and accounting for the different colour–magnitude distributions of training and test data separately can give improved redshift estimates, reduce the bias on estimates by up to a half, and speed up the run-time of the algorithm. These methods are illustrated using data from deep optical and near-infrared data in two separate deep fields, where training and test data of different colour–magnitude distributions are constructed from the galaxies with known spectroscopic redshifts, derived from several heterogeneous surveys.


The relation between the diffuse X-ray luminosity and the radio power of the central AGN in galaxy groups

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 497 (2020) 2163-2174

T Pasini, M Brueggen, F de Gasperin, L Birzan, E O'Sullivan, A Finoguenov, M Jarvis, M Gitti, F Brighenti, IH Whittam, JD Collier, I Heywood, G Gozaliasl


Revealing the Intermediate Mass Black Hole at the Heart of Dwarf Galaxy NGC404 with Sub-parsec Resolution ALMA Observations

Monthly Notices of the Royal Astronomical Society Oxford University Press 496 (2020) 4061-4078

M Bureau, M Cappellari, L Liu, M Smith

We estimate the mass of the intermediate-mass black hole at the heart of the dwarf elliptical galaxy NGC 404 using Atacama Large Millimeter/submillimeter Array (ALMA) observations of the molecular interstellar medium at an unprecedented linear resolution of ≈0.5 pc, in combination with existing stellar kinematic information. These ALMA observations reveal a central disc/torus of molecular gas clearly rotating around the black hole. This disc is surrounded by a morphologically and kinematically complex flocculent distribution of molecular clouds, that we resolve in detail. Continuum emission is detected from the central parts of NGC 404, likely arising from the Rayleigh–Jeans tail of emission from dust around the nucleus, and potentially from dusty massive star-forming clumps at discrete locations in the disc. Several dynamical measurements of the black hole mass in this system have been made in the past, but they do not agree. We show here that both the observed molecular gas and stellar kinematics independently require a ≈ 5 × 105 M black hole once we include the contribution of the molecular gas to the potential. Our best estimate comes from the high-resolution molecular gas kinematics, suggesting the black hole mass of this system is 5.5+4.1−3.8×105 M (at the 99% confidence level), in good agreement with our revised stellar kinematic measurement and broadly consistent with extrapolations from the black hole mass – velocity dispersion and black hole mass – bulge mass relations. This highlights the need to accurately determine the mass and distribution of each dynamically important component around intermediate-mass black holes when attempting to estimate their masses.


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

ASTRONOMY & ASTROPHYSICS 640 (2020) ARTN C4

LK Morabito, JH Matthews, PN Best, G Gurkan, MJ Jarvis, I Prandoni, KJ Duncan, MJ Hardcastle, M Kunert-Bajraszewska, AP Mechev, S Mooney, J Sabater, HJA Rottgering, TW Shimwell, DJB Smith, C Tasse, WL Williams


K-CLASH: Strangulation and ram pressure stripping in galaxy cluster members at 0.3 &lt; z &lt; 0.6

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 496 (2020) 3841-3861

SP Vaughan, AL Tiley, RL Davies, LJ Prichard, SM Croom, M Bureau, JP Stott, A Bunker, M Cappellari, B Ansarinejad, MJ Jarvis

&lt;jats:title&gt;ABSTRACT&lt;/jats:title&gt; &lt;jats:p&gt;Galaxy clusters have long been theorized to quench the star formation of their members. This study uses integral-field unit observations from the K-band MultiObject Spectrograph (KMOS) &#x2013; Cluster Lensing And Supernova survey with Hubble (CLASH) survey (K-CLASH) to search for evidence of quenching in massive galaxy clusters at redshifts 0.3 &amp;amp;lt; z &amp;amp;lt; 0.6. We first construct mass-matched samples of exclusively star-forming cluster and field galaxies, then investigate the spatial extent of their H&#x2009;&#x3B1; emission and study their interstellar medium conditions using emission line ratios. The average ratio of H&#x2009;&#x3B1; half-light radius to optical half-light radius ($r_{\mathrm{e}, {\rm {H}\,\alpha }}/r_{\mathrm{e}, R_{\mathrm{c} } }$) for all galaxies is 1.14&#xA0;&#xB1;&#xA0;0.06, showing that star formation is taking place throughout stellar discs at these redshifts. However, on average, cluster galaxies have a smaller $r_{\mathrm{e}, {\rm {H}\alpha }}/r_{\mathrm{e}, R_{\mathrm{c} } }$ ratio than field galaxies: &#x2329;$r_{\mathrm{e}, {\rm {H}\alpha }}/r_{\mathrm{e}, R_{\mathrm{c} } }$&#x232A;&#xA0;= 0.96&#xA0;&#xB1;&#xA0;0.09 compared to 1.22&#xA0;&#xB1;&#xA0;0.08 (smaller at a 98&#x2009;per&#x2009;cent credibility level). These values are uncorrected for the wavelength difference between H&#x2009;&#x3B1; emission and Rc-band stellar light but implementing such a correction only reinforces our results. We also show that whilst the cluster and field samples follow indistinguishable mass&#x2013;metallicity (MZ) relations, the residuals around the MZ relation of cluster members correlate with cluster-centric distance; galaxies residing closer to the cluster centre tend to have enhanced metallicities (significant at the 2.6&#x3C3; level). Finally, in contrast to previous studies, we find no significant differences in electron number density between the cluster and field galaxies. We use simple chemical evolution models to conclude that the effects of disc strangulation and ram-pressure stripping can quantitatively explain our observations.&lt;/jats:p&gt;


K-CLASH: spatially-resolving star-forming galaxies in field and cluster environments at z ≈ 0.2-0.6

Monthly Notices of the Royal Astronomical Society Oxford University Press (2020)

AL Tiley, JP Stott, R Davies, LJ Prichard, A Bunker, M Bureau, M Cappellari, M Jarvis, A Robotham, L Cortese, S Bellstedt, B Ansarinejad

We present the KMOS-CLASH (K-CLASH) survey, a K-band Multi-Object Spectrograph (KMOS) survey of the spatially-resolved gas properties and kinematics of 191 (predominantly blue) Hα-detected galaxies at 0.2 ≲ z ≲ 0.6 in field and cluster environments. K-CLASH targets galaxies in four Cluster Lensing And Supernova survey with Hubble (CLASH) fields in the KMOS IZ-band, over 7′ radius (≈2–3 Mpc) fields-of-view. K-CLASH aims to study the transition of star-forming galaxies from turbulent, highly star-forming disc-like and peculiar systems at z ≈ 1–3, to the comparatively quiescent, ordered late-type galaxies at z ≈ 0, and to examine the role of clusters in the build-up of the red sequence since z ≈ 1. In this paper, we describe the K-CLASH survey, present the sample, and provide an overview of the K-CLASH galaxy properties. We demonstrate that our sample comprises star-forming galaxies typical of their stellar masses and epochs, residing both in field and cluster environments. We conclude K-CLASH provides an ideal sample to bridge the gap between existing large integral-field spectroscopy surveys at higher and lower redshifts. We find that star-forming K-CLASH cluster galaxies at intermediate redshifts have systematically lower stellar masses than their star-forming counterparts in the field, hinting at possible “downsizing” scenarios of galaxy growth in clusters at these epochs. We measure no difference between the star-formation rates of Hα-detected, star-forming galaxies in either environment after accounting for stellar mass, suggesting that cluster quenching occurs very rapidly during the epochs probed by K-CLASH, or that star-forming K-CLASH galaxies in clusters have only recently arrived there, with insufficient time elapsed for quenching to have occured.


Cold molecular gas and PAH emission in the nuclear and circumnuclear regions of Seyfert galaxies

ASTRONOMY & ASTROPHYSICS 639 (2020)

A Alonso-Herrero, M Pereira-Santaella, D Rigopoulou, I Garcia-Bernete, S Garcia-Burillo, AJ Dominguez-Fernandez, F Combes, RI Davies, T Diaz-Santos, D Esparza-Arredondo, O Gonzalez-Martin, A Hernan-Caballero, EKS Hicks, SF Honig, NA Levenson, C Ramos Almeida, PF Roche, D Rosario


The 16th Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra

ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 249 (2020) ARTN 3

R Ahumada, CA Prieto, A Almeida, F Anders, SF Anderson, BH Andrews, B Anguiano, R Arcodia, E Armengaud, M Aubert, S Avila, V Avila-Reese, C Badenes, C Balland, K Barger, JK Barrera-Ballesteros, S Basu, J Bautista, RL Beaton, TC Beers, BIT Benavides, CF Bender, M Bernardi, M Bershady, F Beutler, CM Bidin, J Bird, D Bizyaev, GA Blanc, MR Blanton, M Boquien, J Borissova, J Bovy, WN Brandt, J Brinkmann, JR Brownstein, K Bundy, M Bureau, A Burgasser, E Burtin, M Cano-Diaz, R Capasso, M Cappellari, R Carrera, S Chabanier, W Chaplin, M Chapman, B Cherinka, C Chiappini, PD Choi, SD Chojnowski, H Chung, N Clerc, D Coffey, JM Comerford, J Comparat, L da Costa, M-C Cousinou, K Covey, JD Crane, K Cunha, GDS Ilha, YS Dai, SB Damsted, J Darling, DJW Jr, R Davies, K Dawson, N De, A de la Macorra, ND Lee, AB de Andrade Queiroz, AD Machado, S de la Torre, F Dell'Agli, HDM des Bourboux, AM Diamond-Stanic, S Dillon, J Donor, N Drory, C Duckworth, T Dwelly, G Ebelke, S Eftekharzadeh, AD Eigenbrot, YP Elsworth, M Eracleous, G Erfanianfar, S Escoffier, X Fan, E Farr, JG Fernandez-Trincado, D Feuillet, A Finoguenov, P Fofie, A Fraser-McKelvie, PM Frinchaboy, S Fromenteau, H Fu, L Galbany, RA Garcia, DA Garcia-Hernandez, LAG Oehmichen, J Ge, MAG Maia, D Geisler, J Gelfand, J Goddy, V Gonzalez-Perez, K Grabowski, P Green, CJ Grier, H Guo, J Guy, P Harding, S Hasselquist, AJ Hawken, CR Hayes, F Hearty, S Hekker, DW Hogg, JA Holtzman, D Horta, J Hou, B-C Hsieh, D Huber, JAS Hunt, JI Chitham, J Imig, M Jaber, CEJ Angel, JA Johnson, AM Jones, H Jonsson, E Jullo, Y Kim, K Kinemuchi, CCK Iv, GW Kite, M Klaene, J-P Kneib, JA Kollmeier, H Kong, M Kounkel, D Krishnarao, I Lacerna, T-W Lan, RR Lane, DR Law, J-M Le Goff, HW Leung, H Lewis, C Li, J Lian, L Lin, D Long, P Longa-Pena, B Lundgren, BW Lyke, JT Mackereth, CL MacLeod, SR Majewski, A Manchado, C Maraston, P Martini, T Masseron, KL Masters, S Mathur, RM McDermid, A Merloni, M Merrifield, S Meszaros, A Miglio, D Minniti, R Minsley, T Miyaji, FG Mohammad, B Mosser, E-M Mueller, D Muna, A Munoz-Gutierrez, AD Myers, S Nadathur, P Nair, K Nandra, JC do Nascimento, RJ Nevin, JA Newman, DL Nidever, C Nitschelm, P Noterdaeme, JE O'Connell, MD Olmstead, D Oravetz, A Oravetz, Y Osorio, ZJ Pace, N Padilla, N Palanque-Delabrouille, PA Palicio, H-A Pan, K Pan, J Parker, R Paviot, S Peirani, KP Ramrez, S Penny, WJ Percival, I Perez-Fournon, I Perez-Rafols, P Petitjean, MM Pieri, M Pinsonneault, VJ Poovelil, JT Povick, A Prakash, AM Price-Whelan, MJ Raddick, A Raichoor, A Ray, SB Rembold, M Rezaie, RA Riffel, R Riffel, H-W Rix, AC Robin, A Roman-Lopes, C Roman-Zuniga, B Rose, AJ Ross, G Rossi, K Rowlands, KHR Rubin, M Salvato, AG Sanchez, L Sanchez-Menguiano, JR Sanchez-Gallego, C Sayres, A Schaefer, RP Schiavon, JS Schimoia, E Schlafly, D Schlegel, DP Schneider, M Schultheis, A Schwope, H-J Seo, A Serenelli, A Shafieloo, SJ Shamsi, Z Shao, S Shen, M Shetrone, R Shirley, VS Aguirre, JD Simon, MF Skrutskie, A Slosar, R Smethurst, J Sobeck, BC Sodi, D Souto, DV Stark, KG Stassun, M Steinmetz, D Stello, J Stermer, T Storchi-Bergmann, A Streblyanska, GS Stringfellow, A Stutz, G Suarez, J Sun, M Taghizadeh-Popp, MS Talbot, J Tayar, AR Thakar, R Theriault, D Thomas, ZC Thomas, J Tinker, R Tojeiro, HH Toledo, CA Tremonti, NW Troup, S Tuttle, E Unda-Sanzana, M Valentini, J Vargas-Gonzalez, M Vargas-Magana, JA Vazquez-Mata, M Vivek, D Wake, Y Wang, BA Weaver, A-M Weijmans, V Wild, JC Wilson, RF Wilson, N Wolthuis, WM Wood-Vasey, R Yan, M Yang, C Yeche, O Zamora, P Zarrouk, G Zasowski, K Zhang, C Zhao, G Zhao, Z Zheng, Z Zheng, G Zhu, H Zou


The 16th data release of the Sloan Digital Sky Surveys: first release from the APOGEE-2 Southern Survey and full release of eBOSS spectra

Astrophysical Journal Supplement American Astronomical Society 249 (2020) 3

R Ahumada, C Allende Prieto, A Almeida, M Bureau, M Cappellari, R Davies, E-M Mueller, R Smethurst, SDSS-IVC SDSS-IV Collaboration

This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).


The rest-frame UV luminosity function at z≃4 : a significant contribution of AGN to the bright-end of the galaxy population

Monthly Notices of the Royal Astronomical Society Oxford University Press 494 (2020) 1771-1783

N Adams, R Bowler, M Jarvis, B Haussler, R McLure, A Bunker, J Dunlop, A Verma

We measure the rest-frame UV luminosity function (LF) at z ∼ 4 self-consistently over a wide range in absolute magnitude (−27 . MUV . −20). The LF is measured with 46,904 sources selected using a photometric redshift approach over ∼ 6 deg2 of the combined COSMOS and XMM-LSS fields. We simultaneously fit for both AGN and galaxy LFs using a combination of Schechter or Double Power Law (DPL) functions alongside a single power law for the faint-end slope of the AGN LF. We find a lack of evolution in the shape of the bright-end of the LBG component when compared to other studies at z ' 5 and evolutionary recipes for the UV LF. Regardless of whether the LBG LF is fit with a Schechter function or DPL, AGN are found to dominate at MUV < −23.5. We measure a steep faint-end slope of the AGN LF with αAGN = −2.09+0.35 −0.38 (−1.66+0.29 −0.58) when fit alongside a Schechter function (DPL) for the galaxies. Our results suggest that if AGN are morphologically selected it results in a bias to lower number densities. Only by considering the full galaxy population over the transition region from AGN to LBG domination can an accurate measurement of the total LF be attained.


A flexible method for estimating luminosity functions via kernel density estimation

Astrophysical Journal Supplement American Astronomical Society 248 (2020)

Z Yuan, MJ Jarvis, J Wang

We propose a flexible method for estimating luminosity functions (LFs) based on kernel density estimation (KDE), the most popular nonparametric density estimation approach developed in modern statistics, to overcome issues surrounding the binning of LFs. One challenge in applying KDE to LFs is how to treat the boundary bias problem, as astronomical surveys usually obtain truncated samples predominantly due to the flux-density limits of surveys. We use two solutions, the transformation KDE method ( ) and the transformation–reflection KDE method ( ) to reduce the boundary bias. We develop a new likelihood cross-validation criterion for selecting optimal bandwidths, based on which the posterior probability distribution of the bandwidth and transformation parameters for and are derived within a Markov Chain Monte Carlo sampling procedure. The simulation result shows that and perform better than the traditional binning method, especially in the sparse data regime around the flux limit of a survey or at the bright end of the LF. To further improve the performance of our KDE methods, we develop the transformation–reflection adaptive KDE approach ( ). Monte Carlo simulations suggest that it has good stability and reliability in performance, and is around an order of magnitude more accurate than using the binning method. By applying our adaptive KDE method to a quasar sample, we find that it achieves estimates comparable to the rigorous determination in a previous work, while making far fewer assumptions about the LF. The KDE method we develop has the advantages of both parametric and nonparametric methods.


Alma maging of the co (7−6) line emission in the submillimeter galaxy less 073 at z = 4.755

Astrophysical Journal American Astronomical Society 892 (2020) 145

Y Zhao, N Lu, T Diaz-Santos, Y Gao, K Xu, V Charmandaris, H Inami, D Rigopoulou, D Sanders, J Huang, Z Wang

In this paper we present our imaging observations on the CO (7−6) line and its underlying continuum emission of the young submillimeter galaxy LESS 073 at redshift 4.755, using the Atacama Large Millimeter/submillimeter Array (ALMA). At the achieved resolution of ∼1 ′′ .2 × 0 ′′ .9 (8 × 6 kpc2 ), the CO (7−6) emission is largely unresolved (with a deconvolved size of 1′′ .1(±0 ′′ .5) × 0 ′′ .9(±0 ′′ .8).), and the continuum emission is totally unresolved. The CO (7−6) line emission has an integrated flux of 0.86 ± 0.08 Jy km s−1 , and a line width of 343 ± 40 km s−1 . The continuum emission has a flux density of 0.51 mJy. By fitting the observed far-infrared (FIR) spectral energy distribution of LESS 073 with a single-temperature modified blackbody function, we obtained a dust temperature Tdust = 57.6 ± 3.5 K, 60-to-100 µm flux density ratio f60/f100 = 0.86 ± 0.08, and total infrared luminosity LIR = (5.8±0.9)×1012 L⊙. The SED-fit-based f60/f100 is consistent with those estimated from various line ratios as advocated by our earlier work, indicating that those proposed line-ratiobased method can be used to practically derive f60/f100 for high-z sources. The total molecular gas mass of LESS 073 is (3.3 ± 1.7) × 1010 M⊙, and the inferred gas depletion time is about 43 Myr.


The faint radio source population at 15.7 GHz – IV. The dominance of core emission in faint radio galaxies

Monthly Notices of the Royal Astronomical Society Oxford University Press 493 (2020) 2841-2853

I Whittam, DA Green, M Jarvis, JM Riley

We present 15-GHz Karl G. Jansky Very Large Array observations of a complete sample of radio galaxies selected at 15.7 GHz from the Tenth Cambridge (10C) survey. 67 out of the 95 sources (71 per cent) are unresolved in the new observations and lower frequency radio observations, placing an upper limit on their angular size of ∼2 arcsec. Thus, compact radio galaxies, or radio galaxies with very faint jets, are the dominant population in the 10C survey. This provides support for the suggestion in our previous work that low-luminosity (⁠L<1025W~Hz−1⁠) radio galaxies are core dominated, although higher resolution observations are required to confirm this directly. The 10C sample of compact, high-frequency selected radio galaxies is a mixture of high-excitation and low-excitation radio galaxies and displays a range of radio spectral shapes, demonstrating that they are a mixed population of objects.


The MBHBM Project - I: measurement of the central black hole mass in the Dwarf Galaxy NGC 3504 using molecular gas kinematics

Astrophysical Journal American Astronomical Society 892 (2020) 68

DD Nguyen, M den Brok, AC Seth, M Cappellari, M Bureau

We present a dynamical mass measurement of the supermassive black hole (SMBH) in the nearby double-barred spiral galaxy NGC 3504 as part of the Measuring Black Holes in below Milky Way (Msstarf) Mass Galaxies Project. Our analysis is based on Atacama Large Millimeter/submillimeter Array cycle 5 observations of the ${}^{12}\mathrm{CO}(2-1)$ emission line. These observations probe NGC 3504's circumnuclear gas disk (CND). Our dynamical model of the CND simultaneously constrains a black hole (BH) mass of ${1.6}_{-0.4}^{+0.6}\times {10}^{7}$ M⊙, which is consistent with the empirical BH–galaxy scaling relations and a mass-to-light ratio in the H band of 0.44 ± 0.12 (M⊙/${L}_{\odot }$). This measurement also relies on our new estimation of the distance to the galaxy of 32.4 ± 2.1 Mpc using the surface brightness fluctuation method, which is much further than the existing distance estimates. Additionally, our observations detect a central deficit in the ${}^{12}\mathrm{CO}(2-1)$ integrated intensity map with a diameter of 6.3 pc at the putative position of the SMBH. However, we find that a dense gas tracer CS(5 − 4) peaks at the galaxy center, filling in the 12CO(2 − 1)-attenuated hole. Holes like this one are observed in other galaxies, and our observations suggest these may be caused by changing excitation conditions rather than a true absence of molecular gas around the nucleus.


Deceptively cold dust in the massive starburst galaxy GN20 at z~4

Astronomy & Astrophysics EDP Sciences (2020)

D Rigopoulou, F Valentino, E Daddi, D Liu, D Riechers, M Sargent, D Cormier, JA Hodge, M Béthermin, V Kokorev, TR Greve, F Walter, D Elbaz, S Toft, GE Magdis, I Cortzen


The Karl G. Jansky very large array sky survey (VLASS). Science case and survey design

Publications of the Astronomical Society of the Pacific 132 (2020)

M Lacy, SA Baum, CJ Chandler, S Chatterjee, TE Clarke, S Deustua, J English, J Farnes, BM Gaensler, N Gugliucci, G Hallinan, BR Kent, A Kimball, CJ Law, TJW Lazio, J Marvil, SA Mao, D Medlin, K Mooley, EJ Murphy, S Myers, R Osten, GT Richards, E Rosolowsky, L Rudnick

© 2020. The Astronomical Society of the Pacific. The Very Large Array Sky Survey (VLASS) is a synoptic, all-sky radio sky survey with a unique combination of high angular resolution (≈2.″5), sensitivity (a 1σ goal of 70 μJy/beam in the coadded data), full linear Stokes polarimetry, time domain coverage, and wide bandwidth (2–4 GHz). The first observations began in 2017 September, and observing for the survey will finish in 2024. VLASS will use approximately 5500 hr of time on the Karl G. Jansky Very Large Array (VLA) to cover the whole sky visible to the VLA (decl. &gt; −40°), a total of 33 885 deg2. The data will be taken in three epochs to allow the discovery of variable and transient radio sources. The survey is designed to engage radio astronomy experts, multi-wavelength astronomers, and citizen scientists alike. By utilizing an “on the fly” interferometry mode, the observing overheads are much reduced compared to a conventional pointed survey. In this paper, we present the science case and observational strategy for the survey, and also results from early survey observations.

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