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Hunting for galaxies and halos in simulations with VELOCIraptor

  • Pascal J. Elahi (a1) (a2), Rodrigo Cañas (a1) (a2), Rhys J. J. Poulton (a1) (a2), Rodrigo J. Tobar (a1), James S. Willis (a3), Claudia del P. Lagos (a1) (a2), Chris Power (a1) (a2) and Aaron S. G. Robotham (a1)...


We present VELOCIraptor, a massively parallel galaxy/(sub)halo finder that is also capable of robustly identifying tidally disrupted objects and separate stellar halos from galaxies. The code is written in C++11, use the Message Passing Interface (MPI) and OpenMP Application Programming Interface (API) for parallelisation, and includes python tools to read/manipulate the data products produced. We demonstrate the power of the VELOCIraptor (sub)halo finder, showing how it can identify subhalos deep within the host that have negligible density contrasts to their parent halo. We find a subhalo mass-radial distance dependence: large subhalos with mass ratios of ≳10−2 are more common in the central regions than smaller subhalos, a result of dynamical friction and low tidal mass loss rates. This dependence is completely absent in (sub)halo finders in common use, which generally search for substructure in configuration space, yet is present in codes that track particles belonging to halos as they fall into other halos, such as hbt+. VELOCIraptor largely reproduces the dependence seen without tracking, finding a similar radial dependence to hbt+ in well-resolved halos from our limited resolution fiducial simulation.


Corresponding author

Author for correspondence: Pascal J. Elahi, E-mail:


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Allgood, B., Flores, R. A., Primack, J. R., Kravtsov, A. V., Wechsler, R. H., Faltenbacher, A., & Bullock, J. S. 2006, MNRAS, 367, 1781
Appel, A. 1985, SIAM J. Sci. Stat. Comput., 6, 85
Arthur, J., et al. 2017, MNRAS, 464, 2027
Barnes, J., & Hut, P. 1986, Nature, 324, 446
Behroozi, P. S., Wechsler, R. H., & Wu, H.-Y. 2013, ApJ, 762, 109
Behroozi, P., et al. 2015, MNRAS, 454, 3020
Bryan, G. L., & Norman, M. L. 1998, ApJ, 495, 80
Bullock, J. S., Kolatt, T. S., Sigad, Y., Somerville, R. S., Kravtsov, A. V., Klypin, A. A., Primack, J. R., & Dekel, A. 2001, MNRAS, 321, 559
Cañas, R., Elahi, P. J., Welker, C., Lagos, C. d. P., Power, C., Dubois, Y., & Pichon, C. 2018, preprint, arXiv:1806.11417
Castro-Ginard, A., Jordi, C., Luri, X., Julbe, F., Morvan, M., Balaguer-Núñez, L., & Cantat-Gaudin, T. 2018, preprint, arXiv:1805.03045
Davis, M., Efstathiou, G., Frenk, C. S., & White, S. D. M. 1985, ApJ, 292, 371
Diemer, B., & Kravtsov, A. V. 2014, ApJ, 789, 1
Diemer, B., Mansfield, P., Kravtsov, A. V., & More, S. 2017, ApJ, 843, 140
Dubinski, J., & Carlberg, R. G. 1991, ApJ, 378, 496
Elahi, P. J., Thacker, R. J., & Widrow, L. M. 2011, MNRAS, 418, 320
Elahi, P. J., et al. 2013, MNRAS, 433, 1537
Elahi, P. J., et al. 2016, MNRAS, 458, 1096
Elahi, P. J., Welker, C., Power, C., Lagos, C. d. P., Robotham, A. S. G., Cañas, R., & Poulton, R. 2018, MNRAS, 475, 5338
Elahi, P. J., Poulton, R. J. J., Tobar, R. J., Lagos, C. d. P., Power, C., & Robotham, A. S. G. 2019, arXiv e-prints, arXiv:1902.01527
Foreman-Mackey, D., Hogg, D. W., Lang, D., & Goodman, J. 2013, PASP, 125, 306
Friedman, J. H., Bentley, J. L., & Finkel, R. A. 1977, ACM Trans. Math. Softw., 3, 209
Collaboration, G., et al. 2018, preprint, arXiv:1804.09380
Gao, L., Navarro, J. F., Frenk, C. S., Jenkins, A., Springel, V., & White, S. D. M. 2012, MNRAS, 425, 2169
Han, J., Cole, S., Frenk, C. S., & Jing, Y. 2016, MNRAS, 457, 1208
Han, J., Cole, S., Frenk, C. S., Benitez-Llambay, A., & Helly, J. 2018, MNRAS, 474, 604
Hawkins, K., & Wyse, R. F. G. 2018, preprint, arXiv:1806.07907
Hunter, J. D. 2007, Comput.Sci.Eng., 9, 90
Jones, E., et al. 2001, SciPy: open source scientific tools for Python,
Knebe, A., et al. 2011, MNRAS, 415, 2293
Knebe, A., et al. 2013a, MNRAS, 428, 2039
Knebe, A., et al. 2013b, MNRAS, 435, 1618
Knollmann, S. R., & Knebe, A. 2009, ApJS, 182, 608
Kuijken, K., & Dubinski, J. 1995, MNRAS, 277, 1341
Lacey, C., & Cole, S. 1994, MNRAS, 271, 676
Lindegren, L., et al. 2018, preprint, arXiv:1804.09366
Maciejewski, M., Colombi, S., Springel, V., Alard, C., & Bouchet, F. R. 2009, MNRAS, 396, 1329
Madau, P., Diemand, J., & Kuhlen, M. 2008, ApJ, 679, 1260
Marchetti, T., Rossi, E. M., & Brown, A. G. A. 2018, preprint, arXiv:1804.10607
Muldrew, S. I., Pearce, F. R., & Power, C. 2011, MNRAS, 410, 2617
Murray, S. G., Power, C., & Robotham, A. S. G. 2013, A&C, 3, 23
N-Body Shop 2011, TIPSY: Code for Display and Analysis of N-body Simulations, Astrophysics Source Code Library (ascl:1111.015)
Navarro, J.F., Frenk, C.S., & White, S.D.M. 1997, ApJ, 490, 493
Onions, J., et al. 2012, MNRAS, 423, 1200
Pedregosa, F., et al. 2011, J. Mach. Learn. Res., 12, 2825
Power, C., Navarro, J. F., Jenkins, A., Frenk, C. S., White, S. D. M., Springel, V., Stadel, J., & Quinn, T. 2003, MNRAS, 338, 14
Prada, F., Klypin, A. A., Cuesta, A. J., Betancort-Rijo, J. E., & Primack, J. 2012, MNRAS, 423, 3018
Price-Whelan, A. M., & Bonaca, A. 2018, preprint, arXiv:1805.00425
Rodríguez-Puebla, A., Behroozi, P., Primack, J., Klypin, A., Lee, C., & Hellinger, D. 2016, MNRAS, 462, 893
Sales, L. V., Navarro, J. F., Schaye, J., Dalla Vecchia, C., Springel, V., & Booth, C. M. 2010, MNRAS, 409, 1541
Schaller, M., Gonnet, P., Chalk, A. B. G., & Draper, P. W. 2016, in Proceedings of the Platform for Advanced Scientific Computing Conference, PASC 2016 (New York, NY, USA: ACM), 2:1, doi: 10.1145/2929908.2929916
Sharma, S., & Steinmetz, M. 2006, MNRAS, 373, 1293
Sheth, R. K., Mo, H. J., & Tormen, G. 2001, MNRAS, 323, 1
Springel, V. 2005, MNRAS, 364, 1105
Springel, V. 2010, MNRAS, 401, 791
Springel, V., White, S. D. M., Tormen, G., & Kauffmann, G. 2001, MNRAS, 328, 726
Springel, V., et al. 2005, Nature, 435, 629
Springel, V., et al. 2008, MNRAS, 391, 1685
Stadel, J., Potter, D., Moore, B., Diemand, J., Madau, P., Zemp, M., Kuhlen, M., & Quilis, V. 2009, MNRAS, 398, L21
Teyssier, R. 2002, A&A, 385, 337
Tinker, J. L., Robertson, B. E., Kravtsov, A. V., Klypin, A., Warren, M. S., Yepes, G., & Gottlöber, S. 2010, ApJ, 724, 878
Tweed, D., Devriendt, J., Blaizot, J., Colombi, S., & Slyz, A. 2009, A&A, 506, 647
Vogelsberger, M., et al. 2009, MNRAS, 395, 797
Watson, W. A., Iliev, I. T., D’Aloisio, A., Knebe, A., Shapiro, P. R., & Yepes, G. 2013, MNRAS, 433, 1230
Widrow, L. M., & Dubinski, J. 2005, ApJ, 631, 838
Widrow, L. M., Pym, B., & Dubinski, J. 2008, ApJ, 679, 1239
van den Bosch, F. C., & Jiang, F. 2016, MNRAS, 458, 2870



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