Supermassive black hole formation in the initial collapse of axion dark matter

Axion dark matter thermalizes by gravitational self-interactions and forms a Bose-Einstein condensate. We show that the rethermalization of the axion fluid during the initial collapse of large scale overdensities near cosmic dawn transports angular momentum outward sufficiently fast that black holes form with masses ranging from approximately <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msup> <a:mn>10</a:mn> <a:mn>5</a:mn> </a:msup> </a:math> to a few times <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:msup> <c:mn>10</c:mn> <c:mn>10</c:mn> </c:msup> <c:msub> <c:mi>M</c:mi> <c:mo stretchy="false">⊙</c:mo> </c:msub> </c:math> . This conclusion holds for QCD axions and for axionlike particles of mass larger than <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"> <f:msup> <f:mn>10</f:mn> <f:mrow> <f:mo>−</f:mo> <f:mn>16</f:mn> </f:mrow> </f:msup> <f:mtext> </f:mtext> <f:mtext> </f:mtext> <f:mi>eV</f:mi> <f:mo>/</f:mo> <f:msup> <f:mi>c</f:mi> <f:mn>2</f:mn> </f:msup> </f:math> .