Detecting intermediate-mass black holes in Milky Way globular clusters and the Local Volume with LISA and other gravitational wave detectors. (arXiv:2007.13746v1 [astro-ph.GA])

Detecting intermediate-mass black holes in Milky Way globular clusters and the Local Volume with LISA and other gravitational wave detectors. (arXiv:2007.13746v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Arca_Sedda_M/0/1/0/all/0/1">Manuel Arca-Sedda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Amaro_Seoane_P/0/1/0/all/0/1">Pau Amaro-Seoane</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_X/0/1/0/all/0/1">Xian Chen</a>

The next generation of gravitational wave (GW) observatories would enable the
detection of intermediate mass ratio inspirals (IMRIs), tight binaries composed
of an intermediate-mass black hole (IMBH) and a compact stellar object. Here,
we study the formation of IMRIs triggered by the interactions between two
stellar BHs and an IMBH inhabiting the centre of a globular cluster via direct
$N$-body models. Varying the IMBH mass, the stellar BH mass spectrum, and the
star cluster properties, we find that IMRIs’ formation probability depends on
the initial conditions adopted, attaining overall values $sim5-50%$. Merging
IMRIs tend to map the stellar BH mass spectrum, thus suggesting that their
detections can provide clues about the co-evolution of IMBHs and stellar BHs.
Given the post-merger GW recoil, typical globular clusters containing an IMBH
with mass $M_{rm IMBH}gtrsim 10^3$ M$_odot$ have a retention probability
$>50%$ only if the companion has a mass $M_{rm BH}leq 30$ M$_odot$. Lower
IMBHs are ejected from the cluster if $M_{rm BH}>10$ M$_odot$. At masses
$M_{rm IMBH}=10^2-10^3$ M$_odot$, the remnant spin is strongly affected by
the spin of the companion, whereas for $M_{rm IMBH}>10^4$ M$_odot$ it is
preserved upon multiple mergers. In a 4 yr long mission, we suggest that LISA
can unravel IMBHs in Milky Way globular clusters with a signal-to-noise ratio
SNR$=10-100$, or in the Large Magellanic Cloud (SNR$=8-40$). Our inferred
merger rate suggests that LIGO could detect $0.9-2.5$ yr$^{-1}$ IMRIs with
$M_{rm IMBH}sim100$ M$_odot$, whereas for LISA we find $6-60$ yr$^{-1}$
detections ($M_{rm IMBH} sim 4times 10^4$ M$_odot$). Future detectors like
Einstein Telescope can deliver up to $10^3$ yr$^{-1}$ IMRIs, whereas DECIGO
might allow $400-3800$ yr$^{-1}$ detections for $M_{rm IMBH}<5times10^4$
M$_odot$.

The next generation of gravitational wave (GW) observatories would enable the
detection of intermediate mass ratio inspirals (IMRIs), tight binaries composed
of an intermediate-mass black hole (IMBH) and a compact stellar object. Here,
we study the formation of IMRIs triggered by the interactions between two
stellar BHs and an IMBH inhabiting the centre of a globular cluster via direct
$N$-body models. Varying the IMBH mass, the stellar BH mass spectrum, and the
star cluster properties, we find that IMRIs’ formation probability depends on
the initial conditions adopted, attaining overall values $sim5-50%$. Merging
IMRIs tend to map the stellar BH mass spectrum, thus suggesting that their
detections can provide clues about the co-evolution of IMBHs and stellar BHs.
Given the post-merger GW recoil, typical globular clusters containing an IMBH
with mass $M_{rm IMBH}gtrsim 10^3$ M$_odot$ have a retention probability
$>50%$ only if the companion has a mass $M_{rm BH}leq 30$ M$_odot$. Lower
IMBHs are ejected from the cluster if $M_{rm BH}>10$ M$_odot$. At masses
$M_{rm IMBH}=10^2-10^3$ M$_odot$, the remnant spin is strongly affected by
the spin of the companion, whereas for $M_{rm IMBH}>10^4$ M$_odot$ it is
preserved upon multiple mergers. In a 4 yr long mission, we suggest that LISA
can unravel IMBHs in Milky Way globular clusters with a signal-to-noise ratio
SNR$=10-100$, or in the Large Magellanic Cloud (SNR$=8-40$). Our inferred
merger rate suggests that LIGO could detect $0.9-2.5$ yr$^{-1}$ IMRIs with
$M_{rm IMBH}sim100$ M$_odot$, whereas for LISA we find $6-60$ yr$^{-1}$
detections ($M_{rm IMBH} sim 4times 10^4$ M$_odot$). Future detectors like
Einstein Telescope can deliver up to $10^3$ yr$^{-1}$ IMRIs, whereas DECIGO
might allow $400-3800$ yr$^{-1}$ detections for $M_{rm IMBH}<5times10^4$
M$_odot$.

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