1932

Abstract

The initial mass function (IMF), describing the distribution of birth masses of stars, plays a pivotal role in establishing the observable properties of galaxies. This article reviews the evidence for variation in the IMF of massive early-type galaxies (ETGs), especially from spectroscopic studies and from dynamical and gravitational lensing measurements over the past decade. The principal conclusions are as follows:

  • ▪   The spectra of massive ETGs depart from the predictions of models with Milky Way–like IMFs in a way that is best reproduced by assuming a steeper (bottom-heavy) IMF below ∼1 M.
  • ▪   Lensing and dynamical models, assuming a constant mass-to-light ratio for the stellar component, infer heavy IMFs, superficially supporting the result from spectra.
  • ▪   The spectroscopic signal exhibits a steep gradient, however, and may be confined to the innermost region with scales ≲2 kpc; such internal variation in the stellar mass-to-light ratio would invalidate a key assumption of most dynamics and lensing studies.
  • ▪   For masses above the main sequence turnoff in ancient populations (≳1 M), there is little evidence for a steeper IMF in massive ETGs or their high-redshift progenitors; rather, a slightly shallower slope is preferred in this regime from several different arguments.
  • ▪   Steep internal gradients may be responsible for some of the apparent discrepancies between different methods and also point to the cause of the IMF variation being restricted to conditions specific to the in situ formation phase of ETG cores.

Loading

Article metrics loading...

/content/journals/10.1146/annurev-astro-032620-020217
2020-08-18
2024-04-16
Loading full text...

Full text loading...

/deliver/fulltext/astro/58/1/annurev-astro-032620-020217.html?itemId=/content/journals/10.1146/annurev-astro-032620-020217&mimeType=html&fmt=ahah

Literature Cited

  1. Alatalo K, Davis TA, Bureau M 2013. MNRAS 432:1796–844
  2. Alton PD, Smith RJ, Lucey JR 2017. MNRAS 468:1594–615
  3. Alton PD, Smith RJ, Lucey JR 2018. MNRAS 478:4464–86
  4. Arneson RA, Brownstein JR, Bolton AS 2012. Ap. J. 753:4
  5. Auger MW, Treu T, Bolton AS 2009. Ap. J. 705:1099–115
  6. Auger MW, Treu T, Gavazzi R 2010. Ap. J. Lett. 721:L163–67
  7. Baldry IK, Glazebrook K 2003. Ap. J. 593:258–71
  8. Barber C, Crain RA, Schaye J 2018. MNRAS 479:5448–73
  9. Barber C, Schaye J, Crain RA 2019a. MNRAS 482:2515–29
  10. Barber C, Schaye J, Crain RA 2019b. MNRAS 483:985–1002
  11. Barbuy B, Chiappini C, Gerhard O 2018. Annu. Rev. Astron. Astrophys. 56:223–76
  12. Barnabè M, Spiniello C, Koopmans LVE 2013. MNRAS 436:253–58
  13. Barro G, Faber SM, Pérez-González PG 2013. Ap. J. 765:104
  14. Bastian N, Covey KR, Meyer MR 2010. Annu. Rev. Astron. Astrophys. 48:339–89
  15. Bastian N, Lardo C 2018. Annu. Rev. Astron. Astrophys. 56:83–136
  16. Bate MR 2009. MNRAS 392:1363–80
  17. Baugh CM, Lacey CG, Frenk CS 2005. MNRAS 356:1191–200
  18. Beifiori A, Mendel JT, Chan JCC 2017. Ap. J. 846:120
  19. Belli S, Newman AB, Ellis RS 2014. Ap. J. 783:117
  20. Bernardi M, Sheth RK, Dominguez-Sanchez H 2018. MNRAS 477:2560–71
  21. Blancato K, Genel S, Bryan G 2017. Ap. J. 845:136
  22. Blumenthal GR, Faber SM, Flores R, Primack JR 1986. Ap. J. 301:27–34
  23. Bolton AS, Burles S, Koopmans LVE, Treu T, Moustakas LA 2006. Ap. J. 638:703–24
  24. Bonnell IA, Clarke CJ, Bate MR 2006. MNRAS 368:1296–300
  25. Boroson TA, Thompson IB 1991. Astron. J. 101:111–26
  26. Bressan A, Marigo P, Girardi L 2012. MNRAS 427:127–45
  27. Bryant JJ, Owers MS, Robotham ASG 2015. MNRAS 447:2857–79
  28. Bundy K, Bershady MA, Law DR et al 2015. Ap. J. 798:7
  29. Calamida A, Sahu KC, Casertano S 2015. Ap. J. 810:8
  30. Campbell SW, D'Orazi V, Yong D 2013. Nature 498:198–200
  31. Cappellari M 2016. Annu. Rev. Astron. Astrophys. 54:597–665
  32. Cappellari M, Bacon R, Bureau M 2006. MNRAS 366:1126–50
  33. Cappellari M, Emsellem E, Krajnović D 2011. MNRAS 413:813–36
  34. Cappellari M, McDermid RM, Alatalo K 2012. Nature 484:485–88
  35. Cappellari M, McDermid RM, Alatalo K 2013. MNRAS 432:1862–93
  36. Carter D, Pass S, Kennedy J, Karick AM, Smith RJ 2011. MNRAS 414:3410–23
  37. Carter D, Visvanathan N, Pickles AJ 1986. Ap. J. 311:637–50
  38. Casey CM, Narayanan D, Cooray A 2014. Phys. Rep. 541:45–161
  39. Cenarro AJ, Cardiel N, Gorgas J et al 2001. MNRAS 326:959–80
  40. Cenarro AJ, Gorgas J, Vazdekis A, Cardiel N, Peletier RF 2003. MNRAS 339:L12–16
  41. Chabrier G 2003. Publ. Astron. Soc. Pac. 115:763–95
  42. Chabrier G, Baraffe I 1997. Astron. Astrophys. 327:1039–53
  43. Chabrier G, Hennebelle P, Charlot S 2014. Ap. J. 796:75
  44. Chae KH, Bernardi M, Sheth RK 2018. Ap. J. 860:81
  45. Chantereau W, Usher C, Bastian N 2018. MNRAS 478:2368–87
  46. Choi J, Conroy C, Johnson BD 2019. Ap. J. 872:136
  47. Collett TE, Oldham LJ, Smith RJ 2018. Science 360:1342–46
  48. Collier WP, Smith RJ, Lucey JR 2018. MNRAS 478:1595–600
  49. Collier WP, Smith RJ, Lucey JR 2020. MNRAS 494:271–92
  50. Conroy C 2013. Annu. Rev. Astron. Astrophys. 51:393–455
  51. Conroy C, Graves GJ, van Dokkum PG 2014. Ap. J. 780:33
  52. Conroy C, van Dokkum P 2012a. Ap. J. 747:69
  53. Conroy C, van Dokkum PG 2012b. Ap. J. 760:71
  54. Conroy C, van Dokkum PG, Villaume A 2017. Ap. J. 837:166
  55. Conroy C, Villaume A, van Dokkum PG, Lind K 2018. Ap. J. 854:139
  56. Coulter DA, Lehmer BD, Eufrasio RT 2017. Ap. J. 835:183
  57. Couture J, Hardy E 1993. Ap. J. 406:142–57
  58. Danielson ALR, Swinbank AM, Smail I 2013. MNRAS 436:2793–809
  59. Davis TA, McDermid RM 2017. MNRAS 464:453–68
  60. De Masi C, Vincenzo F, Matteucci F 2019. MNRAS 483:2217–35
  61. de Zeeuw PT, Bureau M, Emsellem E 2002. MNRAS 329:513–30
  62. Domínguez Sánchez H, Bernardi M, Brownstein JR, Drory N, Sheth RK 2019. MNRAS 489:5612–32
  63. Dries M, Trager SC, Koopmans LVE 2016. MNRAS 463:886–912
  64. Dutton AA, Mendel JT, Simard L 2012. MNRAS 422:L33–37
  65. Eichner T, Seitz S, Bauer A 2012. MNRAS 427:1918–39
  66. Faber SM, French HB 1980. Ap. J. 235:405–12
  67. Ferré-Mateu A, Trujillo I, Martín-Navarro I 2017. MNRAS 467:1929–39
  68. Ferreras I, La Barbera F, de La Rosa IG 2013. MNRAS 429:L15–19
  69. Ferreras I, La Barbera F, Vazdekis A 2016. Astron. Geophys. 57:2.32–2.36
  70. Ferreras I, Saha P, Burles S 2008. MNRAS 383:857–63
  71. Ferreras I, Saha P, Leier D, Courbin F, Falco EE 2010. MNRAS 409:L30–34
  72. Ferreras I, Weidner C, Vazdekis A, La Barbera F 2015. MNRAS 448:L82–86
  73. Fontanot F, De Lucia G, Hirschmann M 2017. MNRAS 464:3812–24
  74. Gargiulo ID, Cora SA, Padilla ND 2015. MNRAS 446:3820–41
  75. Geha M, Brown TM, Tumlinson J 2013. Ap. J. 771:29
  76. Gennaro M, Geha M, Tchernyshyov K 2018a. Ap. J. 863:38
  77. Gennaro M, Tchernyshyov K, Brown TM 2018b. Ap. J. 855:20
  78. Goudfrooij P 2018. Ap. J. 857:16
  79. Graves GJ, Faber SM 2010. Ap. J. 717:803–24
  80. Grillmair CJ, Mould JR, Holtzman JA 1998. Astron. J. 115:144–51
  81. Gunawardhana MLP, Hopkins AM, Sharp RG 2011. MNRAS 415:1647–62
  82. Guszejnov D, Hopkins PF, Graus AS 2019. MNRAS 485:4852–62
  83. Henkel C, Mauersberger R 1993. Astron. Astrophys. 274:730–42
  84. Hennebelle P, Chabrier G 2008. Ap. J. 684:395–410
  85. Hopkins AM 2018. Publ. Astron. Soc. Aust. 35:e039
  86. Hopkins PF 2012. MNRAS 423:2037–44
  87. Huchra J, Gorenstein M, Kent S 1985. Astron. J. 90:691–96
  88. Jiménez-Vicente J, Mediavilla E, Kochanek CS, Muñoz JA 2015. Ap. J. 799:149
  89. Kalirai JS, Anderson J, Dotter A 2013. Ap. J. 763:110
  90. Kennicutt RC Jr 1983. Ap. J. 272:54–67
  91. Kochanek CS 2004. Ap. J. 605:58–77
  92. Kroupa P 2001. MNRAS 322:231–46
  93. Krumholz MR 2006. Ap. J. Lett. 641:L45–48
  94. Kuntschner H, Emsellem E, Bacon R 2010. MNRAS 408:97–132
  95. La Barbera F, Ferreras I, Vazdekis A 2015. MNRAS 449:L137–41
  96. La Barbera F, Ferreras I, Vazdekis A 2013. MNRAS 433:3017–47
  97. La Barbera F, Vazdekis A, Ferreras I 2016. MNRAS 457:1468–89
  98. La Barbera F, Vazdekis A, Ferreras I 2017. MNRAS 464:3597–616
  99. La Barbera F, Vazdekis A, Ferreras I 2019. MNRAS 489:4090–110
  100. Lacey CG, Baugh CM, Frenk CS 2016. MNRAS 462:3854–911
  101. Lagattuta DJ, Mould JR, Forbes DA 2017. Ap. J. 846:166
  102. Lagos CP, Robotham ASG, Trayford JW 2019. MNRAS 489:4196–216
  103. Lapenna E, Lardo C, Mucciarelli A 2016. Ap. J. Lett. 826:L1
  104. Leier D, Ferreras I, Saha P 2016. MNRAS 459:3677–92
  105. Li H, Ge J, Mao S 2017. Ap. J. 838:77
  106. Lidman C, Rosati P, Tanaka M 2008. Astron. Astrophys. 489:981–88
  107. Lu JR, Do T, Ghez AM 2013. Ap. J. 764:155
  108. Luhman KL 2004. Ap. J. 617:1216–32
  109. Lyubenova M, Martín-Navarro I, van de Ven G 2016. MNRAS 463:3220–25
  110. Maccarone TJ 2014. MNRAS 442:L5–8
  111. Mancone CL, Gonzalez AH 2012. Publ. Astron. Soc. Pac. 124:606–15
  112. Mandelbaum R, van de Ven G, Keeton CR 2009. MNRAS 398:635–57
  113. Mármol-Queraltó E, Cardiel N, Sánchez-Blázquez P 2009. Ap. J. Lett. 705:L199–203
  114. Martin S, Muller S, Henkel C 2019. Astron. Astrophys. 624:A125
  115. Martín-Navarro I, La Barbera F, Vazdekis A, Falcón-Barroso J, Ferreras I 2015a. MNRAS 447:1033–48
  116. Martín-Navarro I, Lyubenova M, van de Ven G 2019. Astron. Astrophys. 626:A124
  117. Martín-Navarro I, Vazdekis A, La Barbera F 2015b. Ap. J. Lett. 806:L31
  118. McConnell NJ, Lu JR, Mann AW 2016. Ap. J. 821:39
  119. McDermid RM, Cappellari M, Alatalo K 2014. Ap. J. Lett. 792:L37
  120. Mediavilla E, Muñoz JA, Falco E 2009. Ap. J. 706:1451–62
  121. Meneses-Goytia S, Peletier RF, Trager SC, Vazdekis A 2015. Astron. Astrophys. 582:A97
  122. Meyer RE, Sivanandam S, Moon DS 2019. Ap. J. 875:151
  123. Nagashima M, Lacey CG, Okamoto T 2005. MNRAS 363:L31–35
  124. Navarro JF, Frenk CS, White SDM 1996. Ap. J. 462:563–75
  125. Newman AB, Smith RJ, Conroy C, Villaume A, van Dokkum P 2017. Ap. J. 845:157
  126. Newman AB, Treu T, Ellis RS, Sand DJ 2013. Ap. J. 765:25
  127. Offner SSR 2016. In From Interstellar Clouds to Star-Forming Galaxies: Universal Processes?, Vol. 11, IAU Symp. S315, ed. P Jablonka, P André, F van der Tak, pp. 73–80. Cambridge, UK: Cambridge Univ. Press
  128. Oguri M, Rusu CE, Falco EE 2014. MNRAS 439:2494–504
  129. Oldham L, Auger M 2018a. MNRAS 474:4169–85
  130. Oldham LJ, Auger MW 2018b. MNRAS 476:133–50
  131. Oser L, Ostriker JP, Naab T, Johansson PH, Burkert A 2010. Ap. J. 725:2312–23
  132. Padoan P, Nordlund Å 2002. Ap. J. 576:870–79
  133. Parikh T, Thomas D, Maraston C 2018. MNRAS 477:3954–82
  134. Peacock MB, Zepf SE, Kundu A 2017. Ap. J. 841:28
  135. Peacock MB, Zepf SE, Maccarone TJ 2014. Ap. J. 784:162
  136. Percival SM, Salaris M 2009. Ap. J. 703:1123–30
  137. Pfeffer J, Kruijssen JMD, Crain RA, Bastian N 2018. MNRAS 475:4309–46
  138. Pipino A, Matteucci F 2004. MNRAS 347:968–84
  139. Poci A, Cappellari M, McDermid RM 2017. MNRAS 467:1397–413
  140. Pooley D, Rappaport S, Blackburne JA, Schechter PL, Wambsganss J 2012. Ap. J. 744:111
  141. Posacki S, Cappellari M, Treu T, Pellegrini S, Ciotti L 2015. MNRAS 446:493–509
  142. Prichard LJ, Davies RL, Beifiori A 2017. Ap. J. 850:203
  143. Rayner JT, Cushing MC, Vacca WD 2009. Ap. J. Suppl. 185:289–432
  144. Renzini A 2005. In The Initial Mass Function 50 Years Later, ed. E Corbelli, F Palla, H Zinnecker, Ap. Space Sci. Libr. 327:221–30. Dordrecht, Neth.: Springer
  145. Renzini A, Ciotti L 1993. Ap. J. Lett. 416:L49–52
  146. Ricciardelli E, Vazdekis A, Cenarro AJ, Falcón-Barroso J 2012. MNRAS 424:172–89
  147. Röck B, Vazdekis A, La Barbera F 2017. MNRAS 472:361–72
  148. Röck B, Vazdekis A, Ricciardelli E 2016. Astron. Astrophys. 589:A73
  149. Rodriguez-Gomez V, Pillepich A, Sales LV 2016. MNRAS 458:2371–90
  150. Romano D, Matteucci F, Zhang ZY, Papadopoulos PP, Ivison RJ 2017. MNRAS 470:401–15
  151. Rosani G, Pasquali A, La Barbera F, Ferreras I, Vazdekis A 2018. MNRAS 476:5233–52
  152. Saglia RP, Maraston C, Thomas D, Bender R, Colless M 2002. Ap. J. Lett. 579:L13–16
  153. Saglia RP, Sánchez-Blázquez P, Bender R 2010. Astron. Astrophys. 524:A6
  154. Salpeter EE 1955. Ap. J. 121:161–67
  155. Sánchez SF, Kennicutt RC, Gil de Paz A 2012. Astron. Astrophys. 538:A8
  156. Sánchez-Blázquez P, Peletier RF, Jiménez-Vicente J 2006. MNRAS 371:703–18
  157. Sarzi M, Spiniello C, La Barbera F, Krajnović D, van den Bosch R 2018. MNRAS 478:4084–100
  158. Schechter PL, Pooley D, Blackburne JA, Wambsganss J 2014. Ap. J. 793:96
  159. Schechter PL, Wambsganss J 2002. Ap. J. 580:685–95
  160. Schiavon RP 2007. Ap. J. Suppl. 171:146–205
  161. Schiavon RP, Barbuy B, Bruzual AG 2000. Ap. J. 532:453–60
  162. Silva DR, Kuntschner H, Lyubenova M 2008. Ap. J. 674:194–208
  163. Smith RJ 2014. MNRAS 443:L69–73
  164. Smith RJ, Alton P, Lucey JR, Conroy C, Carter D 2015. MNRAS 454:L71–75
  165. Smith RJ, Blakeslee JP, Lucey JR, Tonry J 2005. Ap. J. Lett. 625:L103–6
  166. Smith RJ, Lucey JR 2013. MNRAS 434:1964–77
  167. Smith RJ, Lucey JR, Carter D 2012. MNRAS 426:2994–3007
  168. Smith RJ, Lucey JR, Collier WP 2018. MNRAS 481:2115–24
  169. Smith RJ, Lucey JR, Conroy C 2015. MNRAS 449:3441–57
  170. Smith RJ, Lucey JR, Edge AC 2017. MNRAS 467:836–48
  171. Sonnenfeld A, Jaelani AT, Chan JHH 2019. Astron. Astrophys. 630:A71
  172. Sonnenfeld A, Leauthaud A, Auger MW 2018. MNRAS 481:164–84
  173. Sonnenfeld A, Treu T, Gavazzi R 2012. Ap. J. 752:163
  174. Spiniello C, Trager SC, Koopmans LVE 2015. Ap. J. 803:87
  175. Spiniello C, Trager SC, Koopmans LVE, Chen YP 2012. Ap. J. Lett. 753:L32
  176. Spinrad H 1962. Ap. J. 135:715–35
  177. Spinrad H, Taylor BJ 1971. Ap. J. Suppl. 22:445–84
  178. Talbot MS, Brownstein JR, Bolton AS 2018. MNRAS 477:195–209
  179. Tang B, Worthey G 2015. MNRAS 453:4431–43
  180. Thomas D, Greggio L, Bender R 1999. MNRAS 302:537–48
  181. Thomas D, Maraston C, Bender R 2003a. MNRAS 339:897–911
  182. Thomas D, Maraston C, Bender R 2003b. MNRAS 343:279–83
  183. Thomas J, Saglia RP, Bender R 2011. MNRAS 415:545–62
  184. Treu T 2010. Annu. Rev. Astron. Astrophys. 48:87–125
  185. Treu T, Auger MW, Koopmans LVE 2010. Ap. J. 709:1195–202
  186. Treu T, Koopmans LV, Bolton AS, Burles S, Moustakas LA 2006. Ap. J. 640:662–72
  187. Treu T, Koopmans LVE 2002. Ap. J. 575:87–94
  188. Trujillo I, Feulner G, Goranova Y 2006. MNRAS 373:L36–40
  189. Valdes F, Gupta R, Rose JA, Singh HP, Bell DJ 2004. Ap. J. Suppl. 152:251–59
  190. van den Bosch RCE, van de Ven G 2009. MNRAS 398:1117–28
  191. van Dokkum P, Conroy C, Villaume A, Brodie J, Romanowsky AJ 2017. Ap. J. 841:68
  192. van Dokkum PG 2008. Ap. J. 674:29–50
  193. van Dokkum PG, Conroy C 2010. Nature 468:940–42
  194. Vazdekis A 1999. Ap. J. 513:224–41
  195. Vazdekis A, Casuso E, Peletier RF, Beckman JE 1996. Ap. J. Suppl. 106:307
  196. Vazdekis A, Cenarro AJ, Gorgas J, Cardiel N, Peletier RF 2003. MNRAS 340:1317–45
  197. Vazdekis A, Coelho P, Cassisi S 2015. MNRAS 449:1177–214
  198. Vazdekis A, Koleva M, Ricciardelli E, Röck B, Falcón-Barroso J 2016. MNRAS 463:3409–36
  199. Vazdekis A, Ricciardelli E, Cenarro AJ 2012. MNRAS 424:157–71
  200. Vazdekis A, Sánchez-Blázquez P, Falcón-Barroso J 2010. MNRAS 404:1639–71
  201. Villaume A, Brodie J, Conroy C, Romanowsky AJ, van Dokkum P 2017a. Ap. J. Lett. 850:L14
  202. Villaume A, Conroy C, Johnson B 2017b. Ap. J. Suppl. 230:23
  203. Wegg C, Gerhard O, Portail M 2017. Ap. J. Lett. 843:L5
  204. Weidner C, Ferreras I, Vazdekis A, La Barbera F 2013. MNRAS 435:2274–80
  205. Weidner C, Kroupa P, Pflamm-Altenburg J 2011. MNRAS 412:979–86
  206. Whitford AE 1977. Ap. J. 211:527–38
  207. Wing RF, Ford W. Kent J 1969. Publ. Astron. Soc. Pac. 81:527–29
  208. Worthey G 1994. Ap. J. Suppl. 95:107–49
  209. Wyithe JSB, Turner EL 2001. MNRAS 320:21–30
  210. Wyse RFG, Gilmore G, Houdashelt ML 2002. New Astron. 7:395–433
  211. Zaritsky D, Gil de Paz A, Bouquin AYK 2014. Ap. J. Lett. 780:L1
  212. Zaritsky D, Gil de Paz A, Bouquin AYK 2015. MNRAS 446:2030–37
  213. Zhang ZY, Romano D, Ivison RJ, Papadopoulos PP, Matteucci F 2018. Nature 558:260–63
  214. Zhou S, Mo HJ, Li C 2019. MNRAS 485:5256–75
/content/journals/10.1146/annurev-astro-032620-020217
Loading
/content/journals/10.1146/annurev-astro-032620-020217
Loading

Data & Media loading...

  • Article Type: Review Article
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error