Saved in:
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
|---|---|
| Format: | Preprint |
| Published: |
2026
|
| Subjects: | |
| Online Access: | https://arxiv.org/abs/2602.20247 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866918359021387776 |
|---|---|
| author | Pérez-González, Pablo G. Barro, Guillermo Carniani, Stefano D'Eugenio, Francesco Rieke, George H. Tripodi, Roberta Bunker, Andrew J. Ji, Xihan Marques-Chaves, Rui Schaerer, Daniel Venturi, Giacomo Arévalo-González, Flor Arribas, Santiago Rinaldi, Pierluigi Del Pino, Bruno Rodríguez Witstok, Joris Bhatawdekar, Rachana Boogaard, Leindert A. Charlot, Stephane Chevallard, Jacopo Costantin, Luca Curti, Mirko Curtis-Lake, Emma Daddi, Emanuele Davis, Kelcey Dickinson, Mark Donnan, Callum T. Donnan, Fergus R. Dunlop, James S. Eisenstein, Daniel J. Ferguson, Henry C. Aranda, Román Fernández Finkelstein, Steven L. Fujimoto, Seiji Gandolfi, Giovanni Giavalisco, Mauro Grogin, Norman A. Hamed, Mahmoud Hirschmann, Michaela Kartaltepe, Jeyhan S. Kocevski, Dale D. Koekemoer, Anton M. Leung, Gene C. K. Lofaro, Cristina M. Lucas, Ray A. McLeod, Derek J. Melinder, Jens Östlin, Goran Papovich, Casey Pentericci, Laura Pérez-Díaz, Borja Rieke, Marcia Scholtz, Jan Somerville, Rachel S. Stanton, Thomas M. Stevenson, Struan D. Shivaei, Irene Tacchella, Sandro Trump, Jonathan R. Übler, Hannah Wang, Xin Williams, Christina C. Willmer, Christopher N. A. Yung, L. Y. Aaron Zhu, Yongda |
| author_facet | Pérez-González, Pablo G. Barro, Guillermo Carniani, Stefano D'Eugenio, Francesco Rieke, George H. Tripodi, Roberta Bunker, Andrew J. Ji, Xihan Marques-Chaves, Rui Schaerer, Daniel Venturi, Giacomo Arévalo-González, Flor Arribas, Santiago Rinaldi, Pierluigi Del Pino, Bruno Rodríguez Witstok, Joris Bhatawdekar, Rachana Boogaard, Leindert A. Charlot, Stephane Chevallard, Jacopo Costantin, Luca Curti, Mirko Curtis-Lake, Emma Daddi, Emanuele Davis, Kelcey Dickinson, Mark Donnan, Callum T. Donnan, Fergus R. Dunlop, James S. Eisenstein, Daniel J. Ferguson, Henry C. Aranda, Román Fernández Finkelstein, Steven L. Fujimoto, Seiji Gandolfi, Giovanni Giavalisco, Mauro Grogin, Norman A. Hamed, Mahmoud Hirschmann, Michaela Kartaltepe, Jeyhan S. Kocevski, Dale D. Koekemoer, Anton M. Leung, Gene C. K. Lofaro, Cristina M. Lucas, Ray A. McLeod, Derek J. Melinder, Jens Östlin, Goran Papovich, Casey Pentericci, Laura Pérez-Díaz, Borja Rieke, Marcia Scholtz, Jan Somerville, Rachel S. Stanton, Thomas M. Stevenson, Struan D. Shivaei, Irene Tacchella, Sandro Trump, Jonathan R. Übler, Hannah Wang, Xin Williams, Christina C. Willmer, Christopher N. A. Yung, L. Y. Aaron Zhu, Yongda |
| contents | We compile JWST/NIRSpec prism and MIRI data for 249 Little Red Dots (LRDs) at 2.3<z<9.3, forming a representative spectroscopic subset of NIRCam-selected LRDs. We derive a median stacked spectrum covering rest-frame 0.09-1.2 $μ$m, with MIRI photometry extending the spectral energy distribution to 4 $μ$m. Four additional stacks for subsamples defined by optical-to-UV luminosity ratios show that LRDs form a heterogeneous population spanning diverse continuum slopes and line properties. Assuming LRDs host super-massive black holes (BHs) surrounded by dense gas clouds, and stars accompany this core, we infer masses of $M_{BH}\sim10^{6.0-6.5}$ M$_\odot$ and $M_\bigstar\sim10^{8.3}$ M$_\odot$, corresponding to BH-to-stellar mass ratios of 1-2%. The stacks show ubiquitous UV and optical FeII emission, indicating a direct view of the broad-line region and high (but sub-Eddington) accretion ($λ_{Edd}=0.6\pm0.2$). We find a significant stellar contribution in the far-UV, reaching $\sim80$% in the bluest systems. Possible Wolf-Rayet features (HeII$λ$4687, nitrogen lines) are identified, tracing a young (3-7 Myr) compact starburst event. We also detect strong Balmer breaks and atypical Balmer, Paschen, [OIII], and optical and near-infrared HeI line ratios, and an absorption at $\sim4550$ Angstrom (probably linked to FeII), all consistent with radiative-transfer effects in high-density gas with warm temperatures (4000-7000 K). We find a diversity of LRD flavors modulated by the luminosity ratio between between a short ($\lesssim20$ Myr) and intense phase of BH activity, the most extreme stage lasting $\sim3-7$ Myr, characterized by near-Eddington-limit radiation, and a nuclear and compact starburst dominated by massive stars (even super-massive, $\mathrm{M}_\mathrm{SMS}\sim10^{5}$ M$_\odot$), all embedded in dense gas with modest dust content producing a variety of optical depths. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_20247 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Little Red Dots: One Photometric Tag Concealing Diverse Spectroscopic Flavors of Massive Star Formation and Black Hole Activity Pérez-González, Pablo G. Barro, Guillermo Carniani, Stefano D'Eugenio, Francesco Rieke, George H. Tripodi, Roberta Bunker, Andrew J. Ji, Xihan Marques-Chaves, Rui Schaerer, Daniel Venturi, Giacomo Arévalo-González, Flor Arribas, Santiago Rinaldi, Pierluigi Del Pino, Bruno Rodríguez Witstok, Joris Bhatawdekar, Rachana Boogaard, Leindert A. Charlot, Stephane Chevallard, Jacopo Costantin, Luca Curti, Mirko Curtis-Lake, Emma Daddi, Emanuele Davis, Kelcey Dickinson, Mark Donnan, Callum T. Donnan, Fergus R. Dunlop, James S. Eisenstein, Daniel J. Ferguson, Henry C. Aranda, Román Fernández Finkelstein, Steven L. Fujimoto, Seiji Gandolfi, Giovanni Giavalisco, Mauro Grogin, Norman A. Hamed, Mahmoud Hirschmann, Michaela Kartaltepe, Jeyhan S. Kocevski, Dale D. Koekemoer, Anton M. Leung, Gene C. K. Lofaro, Cristina M. Lucas, Ray A. McLeod, Derek J. Melinder, Jens Östlin, Goran Papovich, Casey Pentericci, Laura Pérez-Díaz, Borja Rieke, Marcia Scholtz, Jan Somerville, Rachel S. Stanton, Thomas M. Stevenson, Struan D. Shivaei, Irene Tacchella, Sandro Trump, Jonathan R. Übler, Hannah Wang, Xin Williams, Christina C. Willmer, Christopher N. A. Yung, L. Y. Aaron Zhu, Yongda Astrophysics of Galaxies We compile JWST/NIRSpec prism and MIRI data for 249 Little Red Dots (LRDs) at 2.3<z<9.3, forming a representative spectroscopic subset of NIRCam-selected LRDs. We derive a median stacked spectrum covering rest-frame 0.09-1.2 $μ$m, with MIRI photometry extending the spectral energy distribution to 4 $μ$m. Four additional stacks for subsamples defined by optical-to-UV luminosity ratios show that LRDs form a heterogeneous population spanning diverse continuum slopes and line properties. Assuming LRDs host super-massive black holes (BHs) surrounded by dense gas clouds, and stars accompany this core, we infer masses of $M_{BH}\sim10^{6.0-6.5}$ M$_\odot$ and $M_\bigstar\sim10^{8.3}$ M$_\odot$, corresponding to BH-to-stellar mass ratios of 1-2%. The stacks show ubiquitous UV and optical FeII emission, indicating a direct view of the broad-line region and high (but sub-Eddington) accretion ($λ_{Edd}=0.6\pm0.2$). We find a significant stellar contribution in the far-UV, reaching $\sim80$% in the bluest systems. Possible Wolf-Rayet features (HeII$λ$4687, nitrogen lines) are identified, tracing a young (3-7 Myr) compact starburst event. We also detect strong Balmer breaks and atypical Balmer, Paschen, [OIII], and optical and near-infrared HeI line ratios, and an absorption at $\sim4550$ Angstrom (probably linked to FeII), all consistent with radiative-transfer effects in high-density gas with warm temperatures (4000-7000 K). We find a diversity of LRD flavors modulated by the luminosity ratio between between a short ($\lesssim20$ Myr) and intense phase of BH activity, the most extreme stage lasting $\sim3-7$ Myr, characterized by near-Eddington-limit radiation, and a nuclear and compact starburst dominated by massive stars (even super-massive, $\mathrm{M}_\mathrm{SMS}\sim10^{5}$ M$_\odot$), all embedded in dense gas with modest dust content producing a variety of optical depths. |
| title | Little Red Dots: One Photometric Tag Concealing Diverse Spectroscopic Flavors of Massive Star Formation and Black Hole Activity |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2602.20247 |