Constraints on freeze-in dark matter from Lyman-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math> forest and 21-cm signal: Single-field models

We report new Lyman-<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>α</a:mi></a:math> and 21-cm constraints on freeze-in dark matter (FIDM) which injects energy into the intergalactic medium either through annihilation or decay to photon(s) or electron-positron pair. With respect to Lyman-<c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>α</c:mi></c:math> we fix the baseline ionization history using low redshift data about astrophysical reionization, whereas for 21-cm signal we adopt the baseline values of 21-cm power spectrum through a standard modeling of star formation developed so far. Using the latest numerical tools, we show that (i) for sterile neutrino FIDM, current Lyman-<e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>α</e:mi></e:math> data and future sensitivity of SKA-low (1000 hrs) on the 21-cm power spectra excludes the FIDM mass up to <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mn>1.8</g:mn><g:mo>×</g:mo><g:msup><g:mn>10</g:mn><g:mrow><g:mo>−</g:mo><g:mn>3</g:mn></g:mrow></g:msup><g:mtext> </g:mtext><g:mtext> </g:mtext><g:mi>GeV</g:mi></g:math> at 95% CL and <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mn>5.46</i:mn><i:mo>×</i:mo><i:msup><i:mn>10</i:mn><i:mrow><i:mo>−</i:mo><i:mn>4</i:mn></i:mrow></i:msup><i:mtext> </i:mtext><i:mtext> </i:mtext><i:mi>GeV</i:mi></i:math>, respectively, and (ii) for millicharged FIDM, current Lyman-<k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mi>α</k:mi></k:math> data only excludes the millicharge down to <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:msup><m:mn>10</m:mn><m:mrow><m:mo>−</m:mo><m:mn>8</m:mn></m:mrow></m:msup></m:math> within the FIDM mass range of <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mrow><o:msup><o:mrow><o:mn>10</o:mn></o:mrow><o:mrow><o:mo>−</o:mo><o:mn>3</o:mn></o:mrow></o:msup><o:mi>–</o:mi><o:mn>1</o:mn><o:mtext> </o:mtext><o:mtext> </o:mtext><o:mi>GeV</o:mi></o:mrow></o:math> at 95% CL, suggesting that the surviving parameter space of millicharged FIDM is still intact. Published by the American Physical Society 2024