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![-Examples of the mid-infrared spectral energy distributions observed for the (R − [24]) ≥ 14 sample. The SEDs range from being power-law dominated (near the top) to exhibiting a distinct "bump" in their SED between 3-10µm (near the bottom). The "bump" is attributed to starlight in the galaxies, peaking at a rest-frame wavelength of ≈1.6µm.](profile/Shane-Bussmann/publication/231019103/figure/fig5/AS:667710333665286@1536205957650/Examples-of-the-mid-infrared-spectral-energy-distributions-observed-for-the-R-24.png)
-Examples of the mid-infrared spectral energy distributions observed for the (R − [24]) ≥ 14 sample. The SEDs range from being power-law dominated (near the top) to exhibiting a distinct "bump" in their SED between 3-10µm (near the bottom). The "bump" is attributed to starlight in the galaxies, peaking at a rest-frame wavelength of ≈1.6µm.
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![Fig. 7.-Top: The observed redshift distribution of all 86 (R − [24]) ≥...](profile/Shane-Bussmann/publication/231019103/figure/fig7/AS:667710333653016@1536205957682/Top-The-observed-redshift-distribution-of-all-86-R-24-14-galaxies-The-dashed_Q320.jpg)
The Spitzer Space Telescope has revealed a significant population of high-redshift (z ~ 2) dust-obscured galaxies with large mid-infrared to ultraviolet luminosity ratios. Due to their optical faintness, these galaxies have been previously missed in traditional optical studies of the distant universe. We present a simple method for selecting this h...
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... "bump", which we interpret as being due to the presence of a stellar continuum peaking at a rest-frame wavelength of 1.6µm. Examples of the two classes of SEDs are shown in figure 5. There is a continuum of SEDs between these two extremes, and it is difficult to define an objective criterion that cleanly discriminates between these two classes, perhaps suggesting that the SEDs in a large fraction of the population are character- ized by both AGN and star-formation activity. ...
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... During the early stages of AGN accretion, the infalling dust and gas can heavily obscure the star formation and accretion disk emission, rendering them difficult to identify at optical wavelengths. The dust, however, re-emits this light at infrared/submillimeter wavelengths, leading to infrared bright populations such as Ultra-Luminous Infrared Galaxies (ULIRGs; Sanders & Mirabel 1996), Submillimeter Galaxies (SMGs; Blain et al. 2002), and Dust-Obscured Galaxies (DOGs; Dey et al. 2008). As the AGN activity intensifies, the surrounding gas and dust are heated and blown out, eventually revealing optical quasars. ...
Hot Dust-Obscured Galaxies (Hot DOGs) are a rare population of hyper-luminous infrared galaxies discovered by the WISE mission. Despite the significant obscuration of the AGN by dust in these systems, pronounced broad and blue-shifted emission lines are often observed. Previous work has shown that 8 Hot DOGs, referred to as Blue-excess Hot DOGs (BHDs), present a blue excess consistent with type 1 quasar emission in their UV-optical SEDs, which has been shown to originate from the light of the obscured central engine scattered into the line of sight. We present an analysis of the rest-frame optical emission characteristics for 172 Hot DOGs through UV-MIR SED modeling and spectroscopic details, with a particular focus on the identification of BHDs. We find that while the optical emission observed in Hot DOGs is in most cases dominated by a young stellar population, 26% of Hot DOGs show a significant enough blue excess emission to be classified as BHDs. Based on their broad CIV and MgII lines, we find that the $M_{\rm BH}$ in BHDs range from $10^{8.7}$ to $10^{10} \ M_{\odot}$. When using the same emission lines in regular Hot DOGs, we find the $M_{\rm BH}$ estimates cover the entire range found for BHDs while also extending to somewhat lower values. This agreement may imply that the broad lines in regular Hot DOGs also originate from scattered light from the central engine, just as in BHDs, although a more detailed study would be needed to rule out an outflow-driven nature. Similar to $z\sim 6$ quasars, we find that Hot DOGs sit above the local relation between stellar and black hole mass, suggesting either that AGN feedback has not yet significantly suppressed the stellar mass growth in the host galaxies, or that they will be outliers of the relation when reaching $z$=0.
... MLAN44 represents one case of the luminous infrared galaxy (LIRGs), a class of objects identified by their high infrared luminosity and faint optical counterparts (e.g., Dey et al. 2008;Wu et al. 2012;Eisenhardt et al. 2012;Liu et al. 2022). In nature, these galaxies are explained by the dust-obscured violent starburst called dust-obscured galaxy (DOG) or obscured AGN activity (hot DOG or Type-II QSO). ...
Circumgalactic Lyman-alpha (Ly$\alpha$) nebulae are gaseous halos around galaxies exhibiting luminous extended Ly$\alpha$ emission. This work investigates Ly$\alpha$ nebulae from deep imaging of $\sim12~\mathrm{deg}^2$ sky, targeted by the MAMMOTH-Subaru survey. Utilizing the wide-field capability of Hyper Suprime-Cam (HSC), we present one of the largest blind Ly$\alpha$ nebula selections, including QSO nebulae, Ly$\alpha$ blobs, and radio galaxy nebulae down to typical $2\sigma$ Ly$\alpha$ surface brightness of $(5-10)\times10^{-18}\mathrm{~erg~s^{-1}~cm^{-2}~arcsec^{-2}}$. The sample contains 117 nebulae with Ly$\alpha$ sizes of 40 - 400 kpc, and the most gigantic one spans about 365 kpc, referred to as the Ivory Nebula. Combining with multiwavelength data, we investigate diverse nebula populations and associated galaxies. We find a small fraction of Ly$\alpha$ nebulae have QSOs ($\sim7\%$), luminous infrared galaxies ($\sim1\%$), and radio galaxies ($\sim 2\%$). Remarkably, among the 28 enormous Ly$\alpha$ nebulae (ELANe) exceeding 100 kpc, about $80\%$ are associated with UV-faint galaxies ($M_\mathrm{UV} > -22$), categorized as Type II ELANe. We underscore that Type II ELANe constitute the majority but remain largely hidden in current galaxy and QSO surveys. Dusty starburst and obscured AGN activity are proposed to explain the nature of Type II ELANe. The SED of stacking all Ly$\alpha$ nebulae also reveals signs of massive dusty star-forming galaxies with obscured AGNs. We propose a model to explain the dusty nature where the diverse populations of Ly$\alpha$ nebula capture massive galaxies at different evolutionary stages undergoing violent assembling. Ly$\alpha$ nebulae provide critical insights into the formation and evolution of today's massive cluster galaxies at cosmic noon.
... Dust-obscured galaxies (DOGs) containing large reservoirs of gas and dust, are arguably thought to be potential hosts of obscured AGN (Narayanan et al. 2010;Suleiman et al. 2022). DOGs are defined to be bright in mid-IR but faint in optical with the flux ratio of 24 µm mid-IR band to R−band optical ( (Dey et al. 2008). In general, DOGs represent the population of optically-faint high-redshift (z ∼ 1.5−2.5) ...
... To select DOGs, we used the conventional criterion of flux ratio of 24 µm to r−band optical ( f 24 µm fr ) ≥ 1000, which corresponds to the colour cut of r − [24] ≥ 7.5, where magnitudes are in the AB system (see Dey et al. 2008;Fiore et al. 2008;Toba et al. 2015). Using the aforementioned criterion, we found a total of 1239 DOGs within 5.3 deg 2 of the XMM-SERVS region. ...
With an aim to unveil the population of obscured AGN hosted in high−z dust−obscured galaxies (DOGs), we performed X-ray spectral study of 34 DOGs (0.59 ≤ z ≤ 4.65) lying within 5.3 deg2 of the XMM−SERVS coverage in the XMM-LSS field. To improve the spectral quality of individual sources, we combined all the existing XMM−Newton data and also included Chandra/ACIS data, whenever available. We find that the X-ray spectra of our DOGs can be fitted with a simple absorbed power law or with a physically-motivated borus02 model. The line-of-sight column densities (NH) in our sources span across a wide range (1.02 × 1022 cm−2 ≤ NH ≤ 1.21 × 1024 cm−2), with a substantial fraction (∼ 17.6 per cent) of them being heavily obscured (NH ≥ 1023 cm−2). We also identified one new CT-AGN candidate, yielding the CT-AGN fraction in our sample to be only 3 per cent. The absorption-corrected 2.0−10 keV X-ray luminosities of our sources (2.00 × 1043 erg s−1 ≤ $L_{\rm 2-10~keV}^{\rm int}$ ≤ 6.17 × 1045 erg s−1) suggest them to be luminous quasars. The NH versus Eddington ratio diagnostic plot infers that our sample consists of a heterogeneous population that includes a small fraction (∼ 12 per cent) of DOGs belonging to an early phase (Hot DOGs) during which accretion and obscuration peaks, while the remaining DOGs belong to an intermediate or late phase during which radiative feedback from the dominant AGN blows away surrounding obscuring material.
... There is a population of dusty AGNs called dust-obscured galaxies (DOGs), which are thought to be in a transition phase between dusty star formation and dusty AGNs after a gas-rich major merger event (Dey et al. 2008). DOGs are AGNs selected by a color between observed-frame optical and MIR. ...
Spatially compact objects with extremely red color in the rest-frame optical to near-infrared (0.4–1 μ m) and blue color in the rest-frame ultraviolet (UV; 0.2–0.4 μ m) have been discovered at 5 < z < 9 using the James Webb Space Telescope (JWST). These extremely red objects (JWST-EROs) exhibit spectral energy distributions (SEDs) that are difficult to explain using a single component of either star-forming galaxies or quasars, leading to two-component models in which the blue UV and extremely red optical are explained using less-dusty and dusty spectra of galaxies or quasars, respectively. Here, we report the remarkable similarity in SEDs between JWST-EROs and blue-excess dust-obscured galaxies (BluDOGs) identified at 2 < z < 3. BluDOGs are a population of active galactic nuclei (AGNs) with black hole masses of ∼10 8–9 M ⊙ , which are 1 order of magnitude larger than those in some JWST-EROs. The Eddington ratios of BluDOGs are 1 or higher, whereas those of JWST-EROs are in the range of 0.1–1. Therefore, JWST-EROs are less massive, less active, and more common counterparts in higher- z of BluDOGs in cosmic noon. Conversely, JWST-EROs have a significantly higher fraction of those with blue excess than DOGs. We present the average UV spectra of BluDOGs as a comparison to JWST-EROs and discuss a coherent evolutionary scenario for dusty AGN populations.
... By selecting systems with robust detections in the WISE W3 and W4 bands (12 and 22 μm, respectively) but marginal or no detections in the W1 and W2 bands (3.4 and 4.6 μm, respectively), a population of hot dust-obscured galaxies (Hot DOGs; Eisenhardt et al. 2012;Wu et al. 2012) powered by highly obscured AGN was discovered in the past decade. Compared with dust-obscured galaxies (DOGs; Dey et al. 2008), Hot DOGs are significantly redder in WISE passbands due to their hotter dust emission heated by the central AGN Bridge et al. 2013), and have much higher bolometric luminosities (Tsai et al. 2015). ...
We report the discovery of the hyperluminous, highly obscured active galactic nuclei (AGN) WISE J190445.04+485308.9 (W1904+4853, hereafter, L bol ∼ 1.1 × 10 ¹³ L ⊙ ) at z = 0.415. Its well-sampled spectral energy distribution (SED) is dominated by infrared dust emission, though broad emission lines are detected in the optical spectra. These features suggest that W1904+4853 contains an actively accreting supermassive black hole hidden in its dusty cocoon, resembling the observed properties of hot dust-obscured galaxies (Hot DOGs), a population previously only identified at z > 1.0. Using the broad component of the Mg ii 2798 Å emission line, we estimate a black hole mass of log ( M BH / M ⊙ ) = 8.4 ± 0.4 . The corresponding Eddington ratio ( η ) of 1.4 − 0.7 + 1.3 implies that the central black hole accretion is at the theoretical limit of isotropic accretion. The rest-frame UV-optical SED also indicates that the host galaxy of W1904+4853 harbors strong star formation activity at the rate of 6–84 M ⊙ yr ⁻¹ with an independent estimate of star formation rate up to ∼45 M ⊙ yr ⁻¹ using the [O ii ] emission line. With an estimated stellar mass of 3 × 10 ¹⁰ M ⊙ , the host galaxy appears to be a starburst system with respect to the main sequence of the star-forming galaxies at the same redshift. Although blueshifted and asymmetric [O iii ] emission provides evidence of an outflow, we estimate it to be an order of magnitude smaller than the star formation rate, indicating that the current obscured AGN activity at the center has not yet produced significant feedback on the host galaxy star formation activity. W1904+4853 supports the interpretation that Hot DOGs are a rare transitional phase of AGN accretion in galaxy evolution, a phase that can persist into the present-day Universe.
... There is a population of dusty AGNs called dustobscured galaxies (DOGs), which are thought to be in a transition phase between dusty star formation and dusty AGNs after a gas-rich major merger event (Dey et al. 2008). DOGs are AGNs selected by a color between observed-frame optical and MIR. ...
Spatially compact objects with extremely red color in the rest-frame optical to near-infrared (0.4--3.0 ${\rm \mu m}$) and blue color in the rest-frame ultraviolet (UV; 0.2--0.4 ${\rm \mu m}$) have been discovered at $5 < z < 9$ using the James Webb Space Telescope (JWST). These extremely red objects (JWST-EROs) exhibit spectral energy distributions (SEDs) that are difficult to explain using a single component of either star-forming galaxies or quasars, leading to two-component models in which the blue UV and extremely red optical are explained using less-dusty and dusty spectra of galaxies or quasars, respectively. Here, we report the remarkable similarity in SEDs between JWST-EROs and blue-excess dust-obscured galaxies (BluDOGs) identified at $2 < z < 3$. BluDOGs are a population of active galactic nuclei (AGNs) with blackhole masses of $\sim10^{8-9}$ M$_\odot$, which are one order of magnitude larger than those in some JWST-EROs. The Eddington accretion rates of BluDOGs are one or higher, whereas those of JWST-EROs are in the range of 0.1--1. Therefore, JWST-EROs are less massive, less active, and more common counterparts in higher-$z$ of BluDOGs in cosmic noon. Conversely, JWST-EROs have a significantly higher fraction of those with blue-excess than DOGs. We present the average UV spectra of BluDOGs as a comparison to JWST-EROs and discuss a coherent evolutionary scenario for dusty AGN populations.
... By selecting systems with robust detections in the WISE W 3 and W 4 bands (12 and 22 µm, respectively) but marginal or no detections in the W 1 and W 2 bands (3.4 and 4.6 µm, respectively), a population of hot dust-obscured galaxies (Hot DOGs; Eisenhardt et al. 2012;Wu et al. 2012) powered by highly obscured AGN was discovered in the past decade. Compared with dust-obscured galaxies (DOGs; Dey et al. 2008), Hot DOGs are significantly redder in WISE passbands due to their hotter dust emission heated by the central AGN Bridge et al. 2013), and have much higher bolometric luminosities (Tsai et al. 2015). ...
We report the discovery of the hyperluminous, highly obscured AGN WISE J190445.04+485308.9 (W1904+4853 hereafter, $L_{bol} = 1.1 \times 10^{13} \ L_{\odot}$) at z=0.415. Its well-sampled spectral energy distribution (SED) is dominated by infrared dust emission, though broad emission lines are detected in the optical spectra. These features suggest that W1904+4853 contains an actively accreting supermassive black hole hidden in its dusty cocoon, resembling the observed properties of Hot Dust-Obscured Galaxies (Hot DOGs), a population previously only identified at z>1.0. Using the broad component of the MgII emission line, we estimate a black hole mass of $log \ (M_{BH}/M_{\odot}) = 8.4 \pm 0.3$. The corresponding Eddington ratio of $1.4 \pm 0.2$ implies that the central black hole accretion is at the theoretical limit of isotropic accretion. The rest-frame UV-optical SED and [O II] emission line also indicate that the host galaxy of W1904+4853 harbors strong star formation activity at the rate of up to $\sim 45 \ M_{\odot} \ yr^{-1}$. With an estimated stellar mass of $3 \times 10^{10} \ M_{\odot}$, the host galaxy appears to be a starburst system with respect to the main sequence of the star-forming galaxies at the same redshift. Although blueshifted and asymmetric [O III] emission provides evidence of an outflow, we estimate it to be an order of magnitude smaller than the star formation rate, indicating that the current obscured AGN activity at the center has not yet produced significant feedback on the host galaxy star formation activity. W1904+4853 supports the interpretation that Hot DOGs are a rare transitional phase of AGN accretion in galaxy evolution, a phase that can persist into the present-day Universe.
... If we combine the SDSS and WISE +Spitzer selections, we obtain a r − W 4 > 13.5 color cut. The effective color cut implied by these criteria is somewhat more stringent than that for the selection of Dust Obscured Galaxies (DOGS; Dey et al. 2008). Previous studies (Brand et al. 2007;Ross et al. 2015) show that this selection uncovers luminous obscured quasars at z ∼ 2. We identified 373 sources from the W4 selection over all fields considered. ...
The census of obscured quasar populations is incomplete, and remains a major unsolved problem, especially at higher redshifts, where we expect a greater density of galaxy formation and quasar activity. We present Gemini GNIRS near-infrared spectroscopy of 24 luminous obscured quasar candidates from the Sloan Digital Sky Survey's Stripe 82 region. The targets were photometrically selected using a WISE/W4 selection technique that is optimized to identify IR-bright and heavily-reddened/optically-obscured targets at $z>1$. We detect emission lines of ${\rm H\alpha}$, ${\rm H\beta}$, and/or ${\rm[ O~III]}$ in 23 sources allowing us to measure spectroscopic redshifts in the range $1<z<3$ with bolometric luminosities spanning $L=10^{46.3}-10^{47.3}$ erg s$^{-1}$. We observe broad $10^3-10^4$ km s$^{-1}$ Balmer emissions with large ${\rm H\alpha}/{\rm H\beta}$ ratios, and we directly observe a heavily reddened rest-frame optical continuum in several sources, suggesting high extinction ($A_V\sim7-20$ mag). Our observations demonstrate that such optical/infrared photometric selection successfully recovers high-redshift obscured quasars. The successful identification of previously undetected red, obscured high-redshift quasar candidates suggests that there are more obscured quasars yet to be discovered.
... By matching our quasar catalog to SDWFS 24 μm photometry, we find that ∼30% of the objects in the the obscured quasar sample would be classified as dust-obscured galaxies (DOGs; Dey et al. 2008) with F 24 /F r > 1000. DOGs are ultraluminous IR galaxies often accompanied by quasar activity at z = 1-2, where the optical emission from both stars and SMBH accretion appears heavily attenuated, implying strong galactic-scale absorption. ...
Obscuration in quasars may arise from steep viewing angles along the dusty torus, or instead may represent a distinct phase of supermassive black hole growth. We test these scenarios by probing the host dark matter halo environments of ∼1.4 million Wide-field Infrared Survey Explorer-selected obscured and unobscured quasars at 〈 z 〉 = 1.4 using angular clustering measurements as well as cross-correlation measurements of quasar positions with the gravitational lensing of the cosmic microwave background. We interpret these signals within a halo occupation distribution framework to conclude that obscured systems reside in more massive effective halos (∼10 12.9 h ⁻¹ M ⊙ ) than their unobscured counterparts (∼10 12.6 h ⁻¹ M ⊙ ), though we do not detect a difference in the satellite fraction. We find excellent agreement between the clustering and lensing analyses and show that this implies the observed difference is robust to uncertainties in the obscured quasar redshift distribution, highlighting the power of combining angular clustering and weak lensing measurements. This finding appears in tension with models that ascribe obscuration exclusively to orientation of the dusty torus along the line of sight, and instead may be consistent with the notion that some obscured quasars are attenuated by galaxy-scale or circumnuclear material during an evolutionary phase.
... A major merger of two gas-rich galaxies is an efficient path to trigger rapid mass accretion onto SMBHs (e.g., Hopkins et al. 2006), although they are expected to be heavily obscured by surrounding dust, which would produce the extremely red color between the optical and infrared (IR) bands, and sometimes they are called dustobscured galaxies (DOGs: e.g., Dey et al. 2008). Our team recently found IR-bright DOGs whose optical to IR color is extremely red with (i − [22]) > 7, where i and [22] are HSC i-band and WISE 22 µm AB magnitudes (Toba et al. 2015(Toba et al. , 2017Noboriguchi et al. 2019) by using Subaru/Hyper Suprime-Cam (HSC: Miyazaki et al. 2018)-Subaru Strategic Program (SSP) wide-field and deep imaging data (Aihara et al. 2018) and archival IR data (ALLWISE). ...
Recent high-$z$ quasar observations strongly indicate that super-Eddington accretion is a crucial phase to describe the existence of supermassive black holes (SMBHs) with $M_\mathrm{BH} \gtrsim 10^9 M_\odot$ at $z \gtrsim 7$. Motivated by the theoretical suggestion that the super-Eddington phase efficiently produces outflows and jets bright in radio bands, we search and find a super-Eddington radio-loud dust-obscured galaxy (DOG) J1406+0102 at $z=0.236$, through cross-matching of the infrared-bright DOGs of Noboriguchi et al. (2019) with the VLA/FIRST 1.4 GHz radio and the SDSS optical spectral catalog. DOG J1406+0102 shows broad components in the Balmer lines. Assuming those lines are from the broad line region, it gives BH mass estimation of $\log\ (M_\mathrm{BH}/M_\odot)=7.30 \pm 0.25$, and AGN luminosity of $\log (L_\mathrm{bol,[OIII]}/\mathrm{erg}~\mathrm{s}^{-1}) = 45.91\pm0.38$ estimated from the intrinsic [OIII] luminosity, resulting in super-Eddington accretion of $\lambda_\mathrm{Edd}\simeq 3$. We show that 1) DOG J1406+0102 is operating strong AGN feedback: the [OIII] outflow velocity exceeds the escape velocity of the host galaxy halo and the kinetic efficiency is obtained as $\approx$ 8% that can be sufficient to quench the host galaxy, 2) the expected future growth pathway of DOG J1406+0102 would join an over-massive BH trajectory and 3) radio-loud DOGs can provide a significant contribution to the high-energy ($\gtrsim$ 100 TeV) cosmic neutrino background if we assume DOG J1406+0102 as a representative of radio-loud DOGs.
