Weekly issue

Week 12, 2025

Mar 17–23, 2025

Week 12, 2025 includes 7 curated papers, centered on QSO, LRD, high-z.

2503.16595v1

Little red dots as young supermassive black holes in dense ionized cocoons

V. Rusakov, D. Watson, G. P. Nikopoulos, G. Brammer, R. Gottumukkala, T. Harvey, K. E. Heintz, R. Damgaard, S. A. Sim, A. Sneppen, A. P. Vijayan, N. Adams, D. Austin, C. J. Conselice, C. M. Goolsby, S. Toft, J. Witstok

Theme match 5/5

Digest

Using the highest-S/N JWST/NIRSpec spectra of LRD-like broad-line sources, the authors show that Balmer-line wings are exponential and symmetric, as expected from electron scattering in a compact, Compton-thick ionized cocoon. Convolving a narrow Doppler core with this scattering kernel yields intrinsic widths of only a few hundred km/s, implying black holes of ~10^5–10^7 M⊙ accreting near the Eddington limit within light‑day–scale gas with mild outflows. Accounting for scattering lowers previous mass estimates by ~2 dex and naturally explains LRD traits, including very weak X-ray/radio via nebular reprocessing. This reframes LRDs as young, rapidly growing SMBHs rather than overmassive quasars for their hosts.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1 (GN 1181-68797): Inspect the semi-log Hα profile—straight, symmetric wings diagnose electron scattering; compare to the poorer double-Gaussian fit and note the P Cygni absorption indicating mild outflow in the cocoon.
Figure 2 (NIRCam stamps): Verify the point-like, very compact morphologies and red rest-optical colors characteristic of LRDs; note the unusual cross-like extension in Object A and rotation seen in its narrow-line 2D spectra.
Figure 3 (sample line fits): Read off intrinsic Doppler FWHM posteriors—most objects cluster at ≈300 km/s while total wings are 1000–2000 km/s from scattering; spot cases with P Cygni/Balmer absorption and the complex profiles of B and G.
Figure 4 (MBH–M★): See how including scattering shifts MBH down by ~2 orders of magnitude into consistency with low-z relations; also note that SED-based M★ are upper limits because optical light is dominated by nebular reprocessing from the cocoon.

Tags

2503.15323v1

Euclid Quick Data Release (Q1). Extending the quest for little red dots to z<4

Euclid Collaboration, L. Bisigello, G. Rodighiero, S. Fotopoulou, F. Ricci, K. Jahnke, A. Feltre, V. Allevato, F. Shankar, P. Cassata, E. Dalla Bontà, G. Gandolfi, G. Girardi, M. Giulietti, A. Grazian, C. C. Lovell, R. Maiolino, T. Matamoro Zatarain, M. Mezcua, I. Prandoni, D. Roberts, W. Roster, M. Salvato, M. Siudek, F. Tarsitano, Y. Toba, A. Vietri, L. Wang, G. Zamorani, M. Baes, S. Belladitta, A. Nersesian, L. Spinoglio, X. Lopez Lopez, N. Aghanim, B. Altieri, A. Amara, S. Andreon, N. Auricchio, H. Aussel, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, A. Basset, P. Battaglia, R. Bender, A. Biviano, A. Bonchi, E. Branchini, M. Brescia, J. Brinchmann, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, A. Da Silva, H. Degaudenzi, G. De Lucia, A. M. Di Giorgio, C. Dolding, H. Dole, F. Dubath, C. A. J. Duncan, X. Dupac, S. Dusini, A. Ealet, S. Escoffier, M. Farina, R. Farinelli, F. Faustini, S. Ferriol, F. Finelli, M. Frailis, E. Franceschi, S. Galeotta, K. George, W. Gillard, B. Gillis, C. Giocoli, P. Gómez-Alvarez, J. Gracia-Carpio, B. R. Granett, F. Grupp, S. Gwyn, S. V. H. Haugan, H. Hoekstra, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, P. Hudelot, M. Jhabvala, E. Keihänen, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, Q. Le Boulc'h, A. M. C. Le Brun, D. Le Mignant, P. Liebing, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. Massey, S. Maurogordato, E. Medinaceli, S. Mei, M. Melchior, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, R. Nakajima, C. Neissner, S. -M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, R. Rebolo, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, E. Rossetti, H. J. A. Rottgering, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, J. A. Schewtschenko, M. Schirmer, P. Schneider, T. Schrabback, M. Scodeggio, A. Secroun, G. Seidel, S. Serrano, P. Simon, C. Sirignano, G. Sirri, L. Stanco, J. Steinwagner, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, A. Zacchei, F. M. Zerbi, I. A. Zinchenko, E. Zucca, M. Ballardini, M. Bolzonella, E. Bozzo, C. Burigana, R. Cabanac, A. Cappi, D. Di Ferdinando, J. A. Escartin Vigo, L. Gabarra, M. Huertas-Company, J. Martín-Fleitas, S. Matthew, M. Maturi, N. Mauri, A. Pezzotta, M. Pöntinen, C. Porciani, I. Risso, V. Scottez, M. Sereno, M. Tenti, M. Viel, M. Wiesmann, Y. Akrami, I. T. Andika, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, C. Benoist, K. Benson, D. Bertacca, M. Bethermin, A. Blanchard, L. Blot, M. L. Brown, S. Bruton, A. Calabro, F. Caro, C. S. Carvalho, T. Castro, Y. Charles, F. Cogato, T. Contini, A. R. Cooray, O. Cucciati, S. Davini, F. De Paolis, G. Desprez, A. Díaz-Sánchez, J. J. Diaz, S. Di Domizio, J. M. Diego, A. Enia, Y. Fang, A. G. Ferrari, P. G. Ferreira, A. Finoguenov, A. Fontana, F. Fontanot, A. Franco, K. Ganga, J. García-Bellido, T. Gasparetto, V. Gautard, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, M. Guidi, C. M. Gutierrez, A. Hall, W. G. Hartley, S. Hemmati, C. Hernández-Monteagudo, H. Hildebrandt, J. Hjorth, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, C. C. Kirkpatrick, S. Kruk, J. Le Graet, L. Legrand, M. Lembo, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, L. Leuzzi, T. I. Liaudat, A. Loureiro, J. Macias-Perez, G. Maggio, M. Magliocchetti, E. A. Magnier, C. Mancini, F. Mannucci, R. Maoli, C. J. A. P. Martins, L. Maurin, M. Miluzio, P. Monaco, C. Moretti, G. Morgante, S. Nadathur, K. Naidoo, A. Navarro-Alsina, S. Nesseris, F. Passalacqua, K. Paterson, L. Patrizii, A. Pisani, D. Potter, S. Quai, M. Radovich, P. -F. Rocci, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, C. Scarlata, J. Schaye, A. Schneider, D. Sciotti, E. Sellentin, A. Shulevski, L. C. Smith, K. Tanidis, C. Tao, G. Testera, R. Teyssier, S. Tosi, A. Troja, M. Tucci, C. Valieri, A. Venhola, D. Vergani, G. Verza, P. Vielzeuf, A. Viitanen, N. A. Walton, J. R. Weaver, E. Soubrie, D. Scott

Theme match 5/5

Digest

Using 63 deg² from Euclid’s Quick Data Release (Q1) plus IRAC and ground-based griz, the team fits two power laws to photometry to isolate little red dots with blue UV and red optical slopes while removing extended sources, strong line emitters, and artifacts. They assemble 3341 LRD candidates at z=0.33–3.6 (29 with IRAC), and derive a rest‑frame UV luminosity function that rises from high z down to z≈1.5–2.5 before declining toward lower redshift. Comparing to quasar UV LFs shows LRDs are not the dominant AGN population at z<4 for M_UV<-21. A noted caveat is that evolution inferred from the IRAC‑detected subsample is limited by small numbers and IRAC’s resolution, motivating follow‑up.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Fig. 1: Check which redshift intervals have sufficient Euclid+IRAC coverage to constrain both UV and optical slopes; the grey and hatched zones show where the two‑power‑law selection is most/least reliable.
Fig. 2: Inspect Euclid and IRAC cutouts for two exemplars to verify compact morphology, look for artifacts or blending (especially in IRAC), and visually confirm the LRD appearance.
Fig. 3: Examine the two‑power‑law SED fits, including upper limits and 16–84% uncertainties, to see how the v‑shaped continuum and derived UV/optical slopes are quantified for individual candidates.
Fig. 4: Compare magnitude distributions across the three fields and four Euclid bands versus the indicated depth markers to judge completeness and where the LRD sample sits relative to survey limits.

Tags

2503.16596v1

A "Black Hole Star" Reveals the Remarkable Gas-Enshrouded Hearts of the Little Red Dots

Rohan P. Naidu, Jorryt Matthee, Harley Katz, Anna de Graaff, Pascal Oesch, Aaron Smith, Jenny E. Greene, Gabriel Brammer, Andrea Weibel, Raphael Hviding, John Chisholm, Ivo Labbé, Robert A. Simcoe, Callum Witten, Hakim Atek, Josephine F. W. Baggen, Sirio Belli, Rachel Bezanson, Leindert A. Boogaard, Sownak Bose, Alba Covelo-Paz, Pratika Dayal, Yoshinobu Fudamoto, Lukas J. Furtak, Emma Giovinazzo, Andy Goulding, Max Gronke, Kasper E. Heintz, Michaela Hirschmann, Garth Illingworth, Akio K. Inoue, Benjamin D. Johnson, Joel Leja, Ecaterina Leonova, Ian McConachie, Michael V. Maseda, Priyamvada Natarajan, Erica Nelson, David J. Setton, Irene Shivaei, David Sobral, Mauro Stefanon, Sandro Tacchella, Sune Toft, Alberto Torralba, Pieter van Dokkum, Arjen van der Wel, Marta Volonteri, Fabian Walter, Bingjie Wang, Darach Watson

Theme match 4/5

Digest

JWST/NIRSpec spectroscopy of the point-like source MoM-BH*-1, observed ~660 Myr after the Big Bang, reveals an enormous Balmer break, broad multi-peaked Hβ, and deep Balmer-line absorption. The authors model it as a “black hole star”: a supermassive black hole enshrouded by extremely dense, turbulent, dust-free gas whose atmosphere imprints the break and absorption while dominating the observed light; narrow [OIII] and residual UV are attributed to a faint host. The data are well matched by a simple Cloudy setup that reproduces the break strength, Balmer EWs, UV faintness, and MIRI continuum, with line ratios consistent with high densities that can collisionally suppress [OIII] and a hint of variability reinforcing the SMBH interpretation. They further argue that Little Red Dots can be explained as BH*s embedded in comparably bright hosts, implying current LRD black hole masses—derived with steep dust corrections and standard scaling relations—may be overestimated by orders of magnitude.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Inspect the NIRCam/MIRI cutouts and NIRSpec prism+G395M spectra to see the sharp Balmer break causing the red NIRCam colors and the deep, aligned Balmer absorption (e.g., Hγ, Hδ) with broad multi-peaked Hβ; note [OIII]-based systemic redshift and the nearly identical slit positions.
Figure 2: Compare MoM-BH*-1’s break strength against quiescent and LRD samples using the [3620–3720]Å and [4000–4100]Å windows; confirm it exceeds the dust-free stellar-population maximum, effectively ruling out a stellar-origin continuum.
Figure 3: Check how the BH* Cloudy model reproduces the smooth Balmer break, Balmer EWs, UV faintness, and MIRI flux with dense, turbulent, dust-free gas; note that narrow [OIII] and extra UV are left to the host and that any excess around H is a modeling artifact from finite Hydrogen levels.
Figure 4: See the BH*+galaxy superposition that mimics an archetypal LRD (V-shaped SED, complex Hβ profile) and the host-subtraction exercise where the residual resembles a BH*; this visually underpins the claim that LRD BH masses and dust estimates are biased high.
Extended Data (variability panel): If present, check the reported ~56-day brightening at rest-optical wavelengths as further SMBH evidence and to gauge any short-timescale changes.

Tags

2503.16600v1

A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at $z=3.5$

Anna de Graaff, Hans-Walter Rix, Rohan P. Naidu, Ivo Labbe, Bingjie Wang, Joel Leja, Jorryt Matthee, Harley Katz, Jenny E. Greene, Raphael E. Hviding, Josephine Baggen, Rachel Bezanson, Leindert A. Boogaard, Gabriel Brammer, Pratika Dayal, Pieter van Dokkum, Andy D. Goulding, Michaela Hirschmann, Michael V. Maseda, Ian McConachie, Tim B. Miller, Erica Nelson, Pascal A. Oesch, David J. Setton, Irene Shivaei, Andrea Weibel, Katherine E. Whitaker, Christina C. Williams

Theme match 4/5

Digest

JWST/NIRSpec+NIRCam+MIRI data on The Cliff, a luminous Little Red Dot at z=3.55, reveal an extreme Balmer break—about twice stronger than any previously seen at high-z—alongside broad Hα (FWHM∼1500 km s⁻¹) and He I emission but no significant metal lines. Stellar-population solutions (even with steep dust or IMF tweaks) fail, and their formal M*∼10^10.5 M⊙ with re∼40 pc would imply implausibly high stellar-collision rates. The spectra and continuum are instead best matched by a “black hole star” configuration: a powerful central ionizing source embedded in dense, absorbing gas that imprints the Balmer edge and Hα absorption while favoring an intrinsically red continuum over heavy dust. This makes The Cliff compelling evidence that at least some LRDs are not ultra-dense galaxies but compact, accretion-powered nuclei shrouded by dense gas.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

NIRSpec 1D/2D spectra around the Balmer edge and Hα: verify the sharp continuum drop near rest 3646 Å (obs. ≈1.66 μm) and inspect the broad Hα profile (FWHM∼1500 km s⁻¹) with superposed absorption; note the absence of strong metal lines.
Rest-UV–to–near-IR SED fit comparison: contrast evolved-stellar, dust-reddened templates versus BH* dense-gas absorption models to see why the latter reproduces the extreme Balmer break and line set.
NIRCam size constraint panel: PSF-convolved morphology showing that a stellar interpretation implies re∼40 pc; check residuals/upper limits on any extended starlight.
MIRI+NIRCam photometry SED: mid-IR points that disfavor heavy dust reddening and instead support an intrinsically red continuum from a compact nucleus.
Model grid/diagnostic figure for dense absorbing gas: how column density and level populations generate the Balmer break and Hα absorption while muting metal lines; locate the parameter space that matches The Cliff.

Tags

2503.15317v1

Euclid Quick Data Release (Q1). First Euclid statistical study of galaxy mergers and their connection to active galactic nuclei

Euclid Collaboration, A. La Marca, L. Wang, B. Margalef-Bentabol, L. Gabarra, Y. Toba, M. Mezcua, V. Rodriguez-Gomez, F. Ricci, S. Fotopoulou, T. Matamoro Zatarain, V. Allevato, F. La Franca, F. Shankar, L. Bisigello, G. Stevens, M. Siudek, W. Roster, M. Salvato, C. Tortora, L. Spinoglio, A. W. S. Man, J. H. Knapen, M. Baes, D. O'Ryan, N. Aghanim, B. Altieri, A. Amara, S. Andreon, N. Auricchio, H. Aussel, C. Baccigalupi, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, A. Bonchi, E. Branchini, M. Brescia, J. Brinchmann, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, A. Costille, F. Courbin, H. M. Courtois, M. Cropper, A. Da Silva, H. Degaudenzi, G. De Lucia, A. M. Di Giorgio, C. Dolding, H. Dole, F. Dubath, C. A. J. Duncan, X. Dupac, A. Ealet, S. Escoffier, M. Fabricius, M. Farina, R. Farinelli, F. Faustini, S. Ferriol, F. Finelli, M. Frailis, E. Franceschi, S. Galeotta, K. George, B. Gillis, C. Giocoli, P. Gómez-Alvarez, J. Gracia-Carpio, B. R. Granett, A. Grazian, F. Grupp, L. Guzzo, S. Gwyn, S. V. H. Haugan, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, P. Hudelot, K. Jahnke, M. Jhabvala, B. Joachimi, E. Keihänen, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, Q. Le Boulc'h, A. M. C. Le Brun, D. Le Mignant, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. Massey, S. Maurogordato, E. Medinaceli, S. Mei, M. Melchior, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, R. Nakajima, C. Neissner, S. -M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, R. Rebolo, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, J. A. Schewtschenko, P. Schneider, T. Schrabback, M. Scodeggio, A. Secroun, G. Seidel, M. Seiffert, S. Serrano, P. Simon, C. Sirignano, G. Sirri, L. Stanco, J. Steinwagner, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, A. Zacchei, G. Zamorani, F. M. Zerbi, I. A. Zinchenko, E. Zucca, M. Ballardini, M. Bolzonella, E. Bozzo, C. Burigana, R. Cabanac, A. Cappi, D. Di Ferdinando, J. A. Escartin Vigo, M. Huertas-Company, J. Martín-Fleitas, S. Matthew, N. Mauri, R. B. Metcalf, A. Pezzotta, M. Pöntinen, C. Porciani, I. Risso, V. Scottez, M. Sereno, M. Tenti, M. Viel, M. Wiesmann, Y. Akrami, S. Alvi, I. T. Andika, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, C. Benoist, K. Benson, D. Bertacca, M. Bethermin, A. Blanchard, L. Blot, H. Böhringer, S. Borgani, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, T. Castro, F. Cogato, S. Conseil, T. Contini, A. R. Cooray, O. Cucciati, S. Davini, F. De Paolis, G. Desprez, A. Díaz-Sánchez, J. J. Diaz, S. Di Domizio, J. M. Diego, P. -A. Duc, A. Enia, Y. Fang, A. G. Ferrari, A. Finoguenov, A. Fontana, F. Fontanot, A. Franco, K. Ganga, J. García-Bellido, T. Gasparetto, V. Gautard, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, M. Guidi, C. M. Gutierrez, A. Hall, W. G. Hartley, C. Hernández-Monteagudo, H. Hildebrandt, J. Hjorth, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, C. C. Kirkpatrick, S. Kruk, J. Le Graet, L. Legrand, M. Lembo, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, L. Leuzzi, T. I. Liaudat, A. Loureiro, J. Macias-Perez, G. Maggio, M. Magliocchetti, E. A. Magnier, F. Mannucci, R. Maoli, C. J. A. P. Martins, L. Maurin, M. Miluzio, P. Monaco, C. Moretti, G. Morgante, K. Naidoo, A. Navarro-Alsina, S. Nesseris, F. Passalacqua, K. Paterson, L. Patrizii, A. Pisani, D. Potter, S. Quai, M. Radovich, P. -F. Rocci, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, C. Scarlata, J. Schaye, A. Schneider, D. Sciotti, E. Sellentin, L. C. Smith, S. A. Stanford, K. Tanidis, G. Testera, R. Teyssier, S. Tosi, A. Troja, M. Tucci, C. Valieri, A. Venhola, D. Vergani, G. Verza, P. Vielzeuf, N. A. Walton, E. Soubrie, D. Scott

Theme match 3/5

Digest

Using Euclid Q1 Deep Fields, the team builds a stellar‑mass–complete (M*>10^9.8 Msun) sample at 0.5<z<2, identifies major mergers with CNNs trained on simulations, and selects AGN via X‑ray, optical spectroscopy, MIR colours, and I_E‑band PSF decompositions. Across all AGN selections, mergers host an AGN excess by factors of 2–6, and the AGN merger fraction rises with point‑source contribution f_PSF up to ~0.55 before declining. In luminosity terms, f_merg increases with L_PSF, exceeding 50% for L_PSF>2×10^43 erg/s at z<0.9 and becoming dominant only above ~10^45 erg/s at z>0.9; for X‑ray AGN, f_merg also increases with L_bol, with AGN mostly in mergers at L_bol>10^45 erg/s. This ties major mergers to the most powerful, dust‑obscured SMBH growth phases, with spectroscopic trends weaker due to small samples.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 2: Inspect Euclid RGB cutouts of merger vs non‑merger classifications to gauge the CNN’s labels and the visibility of tidal asymmetries or close pairs at I_E depth/resolution.
Figure 4: Compare stellar‑mass and f_PSF distributions across AGN selections; use the lower panels to see the rise and turnover near f_PSF≈0.55 that underpins the merger‑activity trend.
Figure 3: Check the L_bol–z coverage for X‑ray and DESI AGN, and where sources exceed L_bol≈10^45 erg/s—the regime where AGN mostly inhabit mergers.
Figure 1: Review TNG mock VIS images to assess how merger features appear in Euclid‑like data across redshift, contextualizing the simulation‑trained CNN classifications.

Tags

2503.17183v1

Halfway to the Peak: ice absorption bands at $z\approx0.5$ with JWST MIRI/MRS

Anna Sajina, Alexandra Pope, Henrik Spoon, Lee Armus, Miriam Eleazer, Duncan Farrah, Mark Lacy, Thomas Lai, Jed McKinney, Sylvain Veilleux, Lin Yan, Jason Young

Theme match 2/5

Digest

JWST/MIRI–MRS spectroscopy of the dusty starburst–AGN composite SSTXFLS J172458.3+591545 (z=0.494) yields the first combined extragalactic detections of CO2, CO, XCN, and H2O ices, with gas‑phase CO alongside solid CO. Ice-band profiles match Galactic/local templates, and their decomposition (polar‑dominated XCN and CO complexes) plus the silicate depth imply a compact, dense, cold nucleus with n>10^5 cm^-3, T≈20–90 K, and A_V≈6–7; [NeV]/[NeVI] confirm a deeply buried AGN. The authors introduce τ_Si versus τ_CO2/τ_Si as a diagnostic that jointly traces total dustiness and dust clumpiness along the line of sight. Together, these results showcase MIRI’s power to map dust composition and geometry well beyond the local Universe.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Check the collapsed channel‑1 cube and the 0.85″ extraction aperture versus the MIRI PSF; in the full spectrum, verify [NeVI] and [NeV] alongside the red‑shaded ice bands and the 12 sub‑band overlap regions.
Figure 2: Inspect the channel‑1 spectrum with the Savitzky–Golay smoothing; confirm the optical z≈0.494 via the alignment of the narrow Br line and locate the rest‑frame positions of H2O, CO2, XCN, and CO absorption.
Figure 3: Compare the target to two nearby-galaxy NIRSpec+MIRI spectra to see how silicate strengths bracket this source and how the stronger hot‑dust continuum signals a more buried nucleus.
Figure 4: Use the zooms on CO2 and XCN+CO to follow the continuum placements, optical‑depth fits, and polar vs. apolar sub‑components—evidence that the polar components dominate and anchor the τ measurements used for density/temperature inferences.

Tags

2503.14739v1

DESI DR2 Results I: Baryon Acoustic Oscillations from the Lyman Alpha Forest

DESI Collaboration, M. Abdul-Karim, J. Aguilar, S. Ahlen, C. Allende Prieto, O. Alves, A. Anand, U. Andrade, E. Armengaud, A. Aviles, S. Bailey, A. Bault, J. Behera, S. BenZvi, D. Bianchi, C. Blake, A. Brodzeller, D. Brooks, E. Buckley-Geer, E. Burtin, R. Calderon, R. Canning, A. Carnero Rosell, P. Carrilho, L. Casas, F. J. Castander, R. Cereskaite, M. Charles, E. Chaussidon, J. Chaves-Montero, D. Chebat, T. Claybaugh, S. Cole, A. P. Cooper, A. Cuceu, K. S. Dawson, R. de Belsunce, A. de la Macorra, A. de Mattia, N. Deiosso, J. Della Costa, A. Dey, B. Dey, Z. Ding, P. Doel, J. Edelstein, D. J. Eisenstein, W. Elbers, P. Fagrelius, K. Fanning, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, C. Garcia-Quintero, L. H. Garrison, E. Gaztañaga, H. Gil-Marín, S. Gontcho A Gontcho, A. X. Gonzalez-Morales, C. Gordon, D. Green, G. Gutierrez, J. Guy, C. Hahn, M. Herbold, H. K. Herrera-Alcantar, M. -F. Ho, K. Honscheid, C. Howlett, D. Huterer, M. Ishak, S. Juneau, N. G. Karaçaylı, R. Kehoe, S. Kent, D. Kirkby, T. Kisner, F. -S. Kitaura, S. E. Koposov, A. Kremin, O. Lahav, C. Lamman, M. Landriau, D. Lang, J. Lasker, J. M. Le Goff, L. Le Guillou, A. Leauthaud, M. E. Levi, Q. Li, T. S. Li, K. Lodha, M. Lokken, C. Magneville, M. Manera, P. Martini, W. L. Matthewson, P. McDonald, A. Meisner, J. Mena-Fernández, R. Miquel, J. Moustakas, D. Muñoz Santos, A. Muñoz-Gutiérrez, A. D. Myers, J. A. Newman, G. Niz, H. E. Noriega, E. Paillas, N. Palanque-Delabrouille, J. Pan, W. J. Percival, I. Pérez-Ràfols, M. M. Pieri, C. Poppett, F. Prada, D. Rabinowitz, A. Raichoor, C. Ramírez-Pérez, M. Rashkovetskyi, C. Ravoux, J. Rich, C. Rockosi, A. J. Ross, G. Rossi, V. Ruhlmann-Kleider, E. Sanchez, N. Sanders, S. Satyavolu, D. Schlegel, M. Schubnell, H. Seo, A. Shafieloo, R. Sharples, J. Silber, F. Sinigaglia, D. Sprayberry, T. Tan, G. Tarlé, P. Taylor, W. Turner, F. Valdes, M. Vargas-Magaña, M. Walther, B. A. Weaver, M. Wolfson, C. Yèche, P. Zarrouk, R. Zhou, H. Zou

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Digest

DESI DR2 doubles the Lyα-forest dataset over DR1, analyzing both the Lyα auto-correlation and the Lyα–QSO cross-correlation from >820k quasar spectra and >1.2M quasar positions. It delivers sub‑percent BAO distances at zeff=2.33: 1.1% radial and 1.3% transverse, for 0.65% isotropic precision, measuring DH/rd=8.632±0.098(stat)±0.026(sys) and DM/rd=38.99±0.52(stat)±0.12(sys). The team details analysis upgrades, validation on improved synthetic data, and refined DLA identification. Motivated by nonlinear BAO shift studies, they include—for the first time in Lyα BAO—a dedicated systematic error term, strengthening high‑z expansion constraints.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1 — Footprint and target statistics: compare the DESI DR2 QSO sky coverage against SDSS-DR16 and inspect the right-panel histogram of repeat observations to gauge DR2 depth and cadence relative to DR1 for Lyα S/N.
Figure 2 — Example DR2 quasar spectrum: locate Lyα forest regions A (1040–1205 Å rest) and B (920–1020 Å), note the placement of C IV/C III metal contamination, and see how a DLA in the sightline is identified/treated for the analysis.
Figure 3 — Lyα auto-correlation (regions A and B): examine the BAO peak across line-of-sight orientation bins (μ; blue near-parallel) and compare solid (fiducial) vs dashed (with broadband terms) fits to see how anisotropic information constrains radial vs transverse scales.
Figure 4 — Lyα–QSO cross-correlation: check the BAO signal’s consistency with the auto case across μ bins and regions A/B, and how the combined modeling tightens the distance constraints while controlling broadband systematics.