No [C II] or dust detection in two Little Red Dots at zspec

article No [C II] or dust detection in two Little Red Dots at zspec > 7 published yes Mengyuan Xiao author Pascal A. Oesch author Longji Bing author David Elbaz author Jorryt J Matthee author 7439a258-f3c0-11ec-9501-9df22fe067200000-0003-2871-127X Yoshinobu Fudamoto author Seiji Fujimoto author Rui Marques-Chaves author Christina C. Williams author Miroslava Dessauges-Zavadsky author Francesco Valentino author Gabriel Brammer author Alba Covelo-Paz author Emanuele Daddi author Johan P.U. Fynbo author Steven Gillman author Michele Ginolfi author Emma Giovinazzo author Jenny E. Greene author Qiusheng Gu author Garth Illingworth author Kohei Inayoshi author Vasily Kokorev author Romain A. Meyer author Rohan P. Naidu author Naveen A. Reddy author Daniel Schaerer author Alice Shapley author Mauro Stefanon author Charles L. Steinhardt author David J. Setton author Marianne Vestergaard author Tao Wang author JoMa department Little Red Dots (LRDs) are compact, point-like sources characterized by their red color and broad Balmer lines; it is a matter of debate whether they are dominated by active galactic nuclei (AGNs) or dusty star-forming galaxies (DSFGs). Here we report two LRDs (ID9094 and ID2756) at zspec > 7 recently discovered in the JWST FRESCO GOODS-North field. Both satisfy the “v-shaped” color and compactness criteria for LRDs and are identified as Type-I AGN candidates based on their broad Hβ emission lines (full width at half maximum: 2280 ± 490 km s−1 for ID9094 and 1070 ± 240 km s−1 for ID2756) and narrow [O III] lines (≃300 − 400 km s−1). To investigate their nature, we conducted deep NOEMA follow-up observations targeting the [C II] 158 μm emission line and the 1.3 mm dust continuum. We do not detect [C II] or 1.3 mm continuum emission for either source. If the two LRDs were DSFGs, we would expect significant detections: > 16σ for [C II] and > 3σ for the 1.3 mm continuum of ID9094, and > 5σ for the [C II] of ID2756. Using the 3σ upper limits of [C II] and 1.3 mm, we performed two analyses: (1) UV-to-far-infrared spectral energy distribution fitting with and without AGN components, and (2) comparison of their properties with the L[C II]–SFRtot empirical relation. Both analyses are consistent with a scenario in which AGN activity contributes to the observed properties, though a dusty star-forming origin cannot be fully ruled out. Our results highlight the importance of far-infrared observations for studying LRDs, a regime that remains largely unexplored. https://research-explorer.ista.ac.at/download/20294/20308/2025_AstronomyAstrophysics_Xiao.pdf application/pdfno EDP Sciences2025 eng Astronomy & Astrophysics 0004-6361 1432-0746 2503.01945 00155917470000410.1051/0004-6361/202554361 700 M. Xiao et al., “No [C II] or dust detection in two Little Red Dots at zspec > 7,” Astronomy & Astrophysics, vol. 700. EDP Sciences, 2025. M. Xiao, P.A. Oesch, L. Bing, D. Elbaz, J.J. Matthee, Y. Fudamoto, S. Fujimoto, R. Marques-Chaves, C.C. Williams, M. Dessauges-Zavadsky, F. Valentino, G. Brammer, A. Covelo-Paz, E. Daddi, J.P.U. Fynbo, S. Gillman, M. Ginolfi, E. Giovinazzo, J.E. Greene, Q. Gu, G. Illingworth, K. Inayoshi, V. Kokorev, R.A. Meyer, R.P. Naidu, N.A. Reddy, D. Schaerer, A. Shapley, M. Stefanon, C.L. Steinhardt, D.J. Setton, M. Vestergaard, T. Wang, Astronomy & Astrophysics 700 (2025). Xiao, M., Oesch, P. A., Bing, L., Elbaz, D., Matthee, J. J., Fudamoto, Y., … Wang, T. (2025). No [C II] or dust detection in two Little Red Dots at zspec > 7. Astronomy & Astrophysics. EDP Sciences. <a href="https://doi.org/10.1051/0004-6361/202554361">https://doi.org/10.1051/0004-6361/202554361</a> Xiao, Mengyuan, et al. “No [C II] or Dust Detection in Two Little Red Dots at Zspec > 7.” Astronomy & Astrophysics, vol. 700, A231, EDP Sciences, 2025, doi:<a href="https://doi.org/10.1051/0004-6361/202554361">10.1051/0004-6361/202554361</a>. Xiao M, Oesch PA, Bing L, et al. No [C II] or dust detection in two Little Red Dots at zspec > 7. Astronomy & Astrophysics. 2025;700. doi:<a href="https://doi.org/10.1051/0004-6361/202554361">10.1051/0004-6361/202554361</a> Xiao, Mengyuan, Pascal A. Oesch, Longji Bing, David Elbaz, Jorryt J Matthee, Yoshinobu Fudamoto, Seiji Fujimoto, et al. “No [C II] or Dust Detection in Two Little Red Dots at Zspec > 7.” Astronomy & Astrophysics. EDP Sciences, 2025. <a href="https://doi.org/10.1051/0004-6361/202554361">https://doi.org/10.1051/0004-6361/202554361</a>. Xiao M, Oesch PA, Bing L, Elbaz D, Matthee JJ, Fudamoto Y, Fujimoto S, Marques-Chaves R, Williams CC, Dessauges-Zavadsky M, Valentino F, Brammer G, Covelo-Paz A, Daddi E, Fynbo JPU, Gillman S, Ginolfi M, Giovinazzo E, Greene JE, Gu Q, Illingworth G, Inayoshi K, Kokorev V, Meyer RA, Naidu RP, Reddy NA, Schaerer D, Shapley A, Stefanon M, Steinhardt CL, Setton DJ, Vestergaard M, Wang T. 2025. No [C II] or dust detection in two Little Red Dots at zspec > 7. Astronomy & Astrophysics. 700, A231. 202942025-09-07T22:01:33Z2026-02-16T12:12:36Z