分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The existence of high-redshift supermassive black holes (SMBHs) -- shining brightly as quasars during the first billion years of our universe -- presents a conundrum in astrophysics. A broad variety of physical mechanisms have been proposed for the formation and rapid growth of these early SMBHs. Promising diagnostics are the relative properties of the black hole and its host galaxy. However, up to now, the detection of stars in quasar host galaxies has been elusive beyond $z>2$, even with deep HST observations. Here, we report the first detections of the stellar component of the host galaxies of two relatively low-luminosity quasars at $z>6$ observed with JWST using NIRCam. After modeling and subtracting the glare from the quasar itself, we find that the host galaxies are massive (stellar mass of $2.5\times$ and $6.3\times10^{10}$ M$_{\odot}$), compact, and disk-like. Unlike most SMBHs in the nearby universe, these quasars are displaced from the centers of their host galaxies in the rest-frame optical, in one case by $0.9$ kpc. These first positive detections of quasar hosts at $z>6$ are a pivotal milestone; we can now assess the stellar environment along with star formation and black hole accretion to determine the physical conditions that govern the formation and evolution of the first SMBHs.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report the multi-wavelength properties of millimeter galaxies hosting X-ray detected active galactic nuclei (AGNs) from the ALMA Lensing Cluster Survey (ALCS). ALCS is an extensive survey of well-studied lensing clusters with ALMA, covering an area of 133 arcmin$^2$ over 33 clusters with a 1.2 mm flux-density limit of ${\sim}$60 $\mathrm{\mu Jy}$ ($1\sigma$). Utilizing the archival data of Chandra, we identify three AGNs at $z=$1.06, 2.09, and 2.84 among the 180 millimeter sources securely detected in the ALCS (of which 155 are inside the coverage of Chandra). The X-ray spectral analysis shows that two AGNs are not significantly absorbed ($\log N_{\mathrm{H}}/\mathrm{cm}^{-2} < 23$), while the other shows signs of moderate absorption ($\log N_{\mathrm{H}}/\mathrm{cm}^{-2}\sim 23.5$). We also perform spectral energy distribution (SED) modelling of X-ray to millimeter photometry. We find that our X-ray AGN sample shows both high mass accretion rates (intrinsic 0.5--8 keV X-ray luminosities of ${\sim}10^{\text{44--45}}\,\mathrm{erg\ s^{-1}}$) and star-formation rates (${\gtrsim}100\,M_{\odot}\,\mathrm{yr}^{-1}$). This demonstrates that a wide-area survey with ALMA and Chandra can selectively detect intense growth of both galaxies and supermassive black holes (SMBHs) in the high-redshift universe.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Infrared quasi-stellar objects (IR QSOs) are a rare subpopulation selected from ultraluminous infrared galaxies (ULIRGs) and have been regarded as promising candidates of ULIRG-to-optical QSO transition objects. Here we present NOEMA observations of the CO(1-0) line and 3 mm continuum emission in an IR QSO IRAS F07599+6508 at $z=0.1486$, which has many properties in common with Mrk 231. The CO emission is found to be resolved with a major axis of $\sim$6.1 kpc that is larger than the size of $\sim$4.0 kpc derived for 3 mm continuum. We identify two faint CO features located at a projected distance of $\sim$11.4 and 19.1 kpc from the galaxy nucleus, respectively, both of which are found to have counterparts in the optical and radio bands and may have a merger origin. A systematic velocity gradient is found in the CO main component, suggesting that the bulk of molecular gas is likely rotationally supported. Based on the radio-to-millimeter spectral energy distribution and IR data, we estimate that about 30$\%$ of the flux at 3 mm arises from free-free emission and infer a free-free-derived star formation rate of 77 $M_\odot\ {\rm yr^{-1}}$, close to the IR estimate corrected for the AGN contribution. We find a high-velocity CO emission feature at the velocity range of about -1300 to -2000 km s$^{-1}$. Additional deep CO observations are needed to confirm the presence of a possible very high-velocity CO extension of the OH outflow in this IR QSO.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Using the novel $JWST$/NIRCam observations in the Abell 2744 field, we present a first spatially resolved overview of an $HST$-dark galaxy, spectroscopically confirmed at $z=2.58$ with magnification $\mu\approx1.9$. While being largely invisible at $\sim$1 $\mu$m with NIRCam, except for sparse clumpy sub-structures, the object is well-detected and resolved in the long-wavelength bands with a spiral shape clearly visible in F277W. By combining ancillary ALMA and $Herschel$ data, we infer that this object is an edge-on dusty spiral with an intrinsic stellar mass log$(M_*/M_\odot)\sim11.3$ and a dust-obscured SFR$\sim 300~M_\odot$~yr$^{-1}$. A massive quiescent galaxy (log$(M_*/M_\odot)\sim10.8$) with tidal features lies 2\farcs{0} away ($r$$\sim$9 kpc), at a consistent redshift as inferred by $JWST$ photometry, indicating a potential major merger. The dusty spiral lies on the main-sequence of star formation, and shows high dust attenuation in the optical ($34$ would be only detectable in F356W and F444W in UNCOVER-like survey, and become totally $JWST$-dark at $z\sim6$. This suggests that detecting highly attenuated galaxies in the Epoch of Reionization might be a challenging task for $JWST$.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: One of the most prominent features of galaxy clusters is the presence of a dominant population of massive ellipticals in their cores. Stellar archaeology suggests that these gigantic beasts assembled most of their stars in the early Universe via starbursts. However, the role of dense environments and their detailed physical mechanisms in triggering starburst activities remain unknown. Here we report spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of the CO $J= 3-2$ emission line, with a resolution of about 2.5 kiloparsecs, toward a forming galaxy cluster core with starburst galaxies at $z=2.51$. In contrast to starburst galaxies in the field often associated with galaxy mergers or highly turbulent gaseous disks, our observations show that the two starbursts in the cluster exhibit dynamically cold (rotation-dominated) gas-rich disks. Their gas disks have extremely low velocity dispersion ($\sigma_{\mathrm{0}} \sim 20-30$ km s$^{-1}$), which is three times lower than their field counterparts at similar redshifts. The high gas fraction and suppressed velocity dispersion yield gravitationally unstable gas disks, which enables highly efficient star formation. The suppressed velocity dispersion, likely induced by the accretion of corotating and coplanar cold gas, might serve as an essential avenue to trigger starbursts in massive halos at high redshifts.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present a statistical study of 180 dust continuum sources identified in 33 massive cluster fields by the ALMA Lensing Cluster Survey (ALCS) over a total of 133 arcmin$^{2}$ area, homogeneously observed at 1.2 mm. ALCS enables us to detect extremely faint mm sources by lensing magnification, including near-infrared (NIR) dark objects showing no counterparts in existing {\it Hubble Space Telescope} and {\it Spitzer} images. The dust continuum sources belong to a blind sample ($N=141$) with S/N $\gtrsim$ 5.0 (a purity of $>$ 0.99) or a secondary sample ($N=39$) with S/N= $4.0-5.0$ screened by priors. With the blind sample, we securely derive 1.2-mm number counts down to $\sim7$ $\mu$Jy, and find that the total integrated 1.2mm flux is 20.7$^{+8.5}_{-6.5}$ Jy deg$^{-2}$, resolving $\simeq$ 80 % of the cosmic infrared background light. The resolved fraction varies by a factor of $0.6-1.1$ due to the completeness correction depending on the spatial size of the mm emission. We also derive infrared (IR) luminosity functions (LFs) at $z=0.6-7.5$ with the $1/V_{\rm max}$ method, finding the redshift evolution of IR LFs characterized by positive luminosity and negative density evolution. The total (=UV+IR) cosmic star-formation rate density (SFRD) at $z>4$ is estimated to be $161^{+25}_{-21}$ % of the established measurements, which were almost exclusively based on optical$-$NIR surveys. Although our general understanding of the cosmic SFRD is unlikely to change beyond a factor of 2, these results add to the weight of evidence for an additional ($\approx 60$ %) SFRD component contributed by the faint-mm population, including NIR dark objects.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present a Spitzer/IRAC survey of H-faint ($H_{160} \gtrsim 26.4$, $<5\sigma$) sources in 101 lensing cluster fields. Across a CANDELS/Wide-like survey area of $\sim$648 arcmin$^2$ (effectively $\sim$221 arcmin$^2$ in the source plane), we have securely discovered 53 sources in the IRAC Channel-2 band (CH2, 4.5 $\mathrm{\mu m}$; median CH2$=22.46\pm0.11$ AB mag) that lack robust HST/WFC3-IR F160W counterparts. The most remarkable source in our sample, namely ES-009 in the field of Abell 2813, is the brightest H-faint galaxy at 4.5 $\mathrm{\mu m}$ known so far ($\mathrm{CH2}=20.48\pm0.03$ AB mag). We show that the H-faint sources in our sample are massive (median $M_\mathrm{star} = 10^{10.3\pm 0.3}$ $M_\odot$), star-forming (median star formation rate $=100_{-40}^{+60}$ $M_\odot$yr$^{-1}$) and dust-obscured ($A_V=2.6\pm0.3$) galaxies around a median photometric redshift of $z=3.9\pm0.4$. The stellar continua of 14 H-faint galaxies can be resolved in the CH2 band, suggesting a median circularized effective radius ($R_\mathrm{e,circ}$; lensing corrected) of $1.9\pm0.2$ kpc and $<1.5$ kpc for the resolved and whole samples, respectively. This is consistent with the sizes of massive unobscured galaxies at $z\sim4$, indicating that H-faint galaxies represent the dusty tail of the distribution of a wider galaxy population. Comparing with the ALMA dust continuum sizes of similar galaxies reported previously, we conclude that the heavy dust obscuration in H-faint galaxies is related to the compactness of both stellar and dust continua ($R_\mathrm{e,circ}\sim 1$ kpc). These H-faint galaxies make up $16_{-7}^{+13}$% of the galaxies in the stellar mass range of $10^{10}-10^{11.2}$ $M_\odot$ at $z=3\sim5$, contributing to $8_{-4}^{+8}$% of the cosmic star formation rate density in this epoch and likely tracing the early phase of massive galaxy formation.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present ALMA deep spectroscopy for a lensed galaxy at $z_{\rm spec}=8.496$ with $\log(M_{\rm star}/M_{\odot})\sim7.8$ whose optical nebular lines and stellar continuum are detected by JWST/NIRSpec and NIRCam Early Release Observations in SMACS0723. Our ALMA spectrum shows [OIII]88$\mu$m and [CII]158$\mu$m line detections at $4.0\sigma$ and $4.5\sigma$, respectively. The redshift and position of the [OIII] line coincide with those of the JWST source, while the [CII] line is blue-shifted by 90 km s$^{-1}$ with a spatial offset of $0.''5$ ($\approx0.5$ kpc in source plane) from the JWST source. The NIRCam F444W image, including [OIII]$\lambda$5007 and H$\beta$ line emission, spatially extends beyond the stellar components by a factor of $>8$. This indicates that the $z=8.5$ galaxy has already experienced strong outflows whose oxygen and carbon produce the extended [OIII]$\lambda$5007 and the offset [CII] emission, which would promote ionizing photon escape and facilitate reionization. With careful slit-loss corrections and removals of emission spatially outside the galaxy, we evaluate the [OIII]88$\mu$m/$\lambda$5007 line ratio, and derive the electron density $n_{\rm e}$ by photoionization modeling to be $220^{+170}_{-100}$ cm$^{-3}$, which is comparable with those of $z\sim2-3$ galaxies. We estimate an [OIII]88$\mu$m/[CII]158$\mu$m line ratio in the galaxy of $>4$, as high as those of known $z\sim6-9$ galaxies. This high [OIII]88$\mu$m/[CII]158$\mu$m line ratio is generally explained by the high $n_{\rm e}$ as well as the low metallicity ($Z_{\rm gas}/Z_{\odot}=0.04^{+0.02}_{-0.02}$), high ionization parameter ($\log U > -2.27$), and low carbon-to-oxygen abundance ratio ($\log$(C/O) $=[-0.52:-0.24]$) obtained from the JWST/NIRSpec data; further [CII] follow-up observations will constrain the covering fraction of photodissociation regions.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report the discovery of a triply-imaged active galactic nucleus (AGN), lensed by the galaxy cluster MACS J0035.4-2015 ($z_{\mathrm{d}}=0.352$). The object is detected in Hubble Space Telescope (HST) imaging taken for the RELICS program. It appears to have a quasi-stellar nucleus consistent with a point-source, with a de-magnified radius of $r_e\lesssim100$ pc. The object is spectroscopically confirmed to be an AGN at $z_{\mathrm{spec}}=2.063\pm0.005$ showing broad rest-frame UV emission lines, and is detected in both X-ray observations with \textit{Chandra} and in ALCS ALMA band 6 (1.2 mm) imaging. It has a relatively faint rest-frame UV luminosity for a quasar-like object, $M_{\mathrm{UV},1450}=-19.7\pm0.2$. The object adds to just a few quasars or other X-ray sources known to be multiply lensed by a galaxy cluster. Some faint, diffuse emission from the host galaxy is also seen around the nucleus, and nearby there is another fainter object sharing the same multiple-imaging symmetry and geometric redshift, which may be an interacting galaxy or a star-forming knot in the host. We present an accompanying lens model, calculate the magnifications and time delays, and infer physical properties for the source. We find the rest-frame UV continuum and emission lines to be dominated by the AGN, and the optical emission to be dominated by the relatively young ($\sim100$ Myr) host galaxy of modest stellar mass $M_{\star}\simeq10^{9.2} \mathrm{M}_{\odot}$. We also observe variations in the AGN's emission, which may suggest that the AGN used to be more active. This object adds a low-redshift counterpart to several relatively faint AGN recently uncovered at high redshifts with HST and JWST.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present an ALMA-Herschel joint analysis of sources detected by the ALMA Lensing Cluster Survey (ALCS) at 1.15 mm. Herschel/PACS and SPIRE data at 100-500 $\mu$m are deblended for 180 ALMA sources in 33 lensing cluster fields that are either detected securely (141 sources; in our main sample) or tentatively at S/N$\geq$4 with cross-matched HST/Spitzer counterparts, down to a delensed 1.15-mm flux density of $\sim0.02$ mJy. We performed far-infrared spectral energy distribution modeling and derived the physical properties of dusty star formation for 125 sources (109 independently) that are detected at $>2\sigma$ in at least one Herschel band. 27 secure ALCS sources are not detected in any Herschel bands, including 17 optical/near-IR-dark sources that likely reside at $z=4.2\pm1.2$. The 16-50-84 percentiles of the redshift distribution are 1.15-2.08-3.59 for ALCS sources in the main sample, suggesting an increasing fraction of $z\simeq1-2$ galaxies among fainter millimeter sources ($f_{1150}\sim 0.1$ mJy). With a median lensing magnification factor of $\mu = 2.6_{-0.8}^{+2.6}$, ALCS sources in the main sample exhibit a median intrinsic star-formation rate of $94_{-54}^{+84}\,\mathrm{M}_\odot\,\mathrm{yr}^{-1}$, lower than that of conventional submillimeter galaxies at similar redshifts by a factor of $\sim$3. Our study suggests weak or no redshift evolution of dust temperature with $L_\mathrm{IR}10^{12}\,\mathrm{L}_\odot$, the dust temperatures show no evolution across $z \simeq 1 -4$ while being lower than those in the local Universe. For the highest-redshift source in our sample ($z=6.07$), we can rule out an extreme dust temperature ($>$80 K) that was reported for MACS0416 Y1 at $z=8.31$.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report on a spectroscopic program to search for dual quasars using Subaru Hyper Suprime-Cam (HSC) images of SDSS quasars which represent an important stage during galaxy mergers. Using Subaru/FOCAS and Gemini-N/GMOS, we identify three new physically associated quasar pairs having projected separations less than 20 kpc, out of 26 observed candidates. These include the discovery of the highest redshift ($z=3.1$) quasar pair with a separation $<$ 10 kpc. Based on the sample acquired to date, the success rate of identifying physically associated dual quasars is $19\%$ when excluding stars based on their HSC colors. Using the full sample of six spectroscopically confirmed dual quasars, we find that the black holes in these systems have black hole masses ($M_{BH} \sim 10^{8-9}M_{\odot}$) similar to single SDSS quasars as well as their bolometric luminosities and Eddington ratios. We measure the stellar mass of their host galaxies based on 2D image decomposition of the five-band ($grizy$) optical emission and assess the mass relation between supermassive black holes (SMBHs) and their hosts. Dual SMBHs appear to have elevated masses relative to their host galaxies. Thus mergers may not necessarily align such systems onto the local mass relation, as suggested by the Horizon-AGN simulation. This study suggests that dual luminous quasars are triggered prior to the final coalescence of the two SMBHs, resulting in early mass growth of the black holes relative to their host galaxies.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present updated measurements of the [O III] 88 $\mu$m, [C II] 158 $\mu$m,
and dust continuum emission from a star-forming galaxy at $z=7.212$,
SXDF-NB1006-2, by utilizing Atacama Large Millimeter/submillimeter Array (ALMA)
archival data sets analysed in previous studies and data sets that have not
been analysed before. The follow-up ALMA observations with higher angular
resolution and sensitivity reveal a clumpy structure of the [O III] emission on
a scale of $0.32-0.85\,\rm{kpc}$. We also combined all the ALMA [O III] ([C
II]) data sets and updated the [O III] ([C II]) detection to $5.9\sigma$
($3.6\sigma-4.5\sigma$). The non-detection of [C II] with data from the REBELS
large program implies the incompleteness of spectral-scan surveys using [C II]
to detect galaxies with high star formation rates (SFRs) but marginal [C II]
emission at high-$z$. The dust continuum at 90 $\mu$m and 160 $\mu$m remains
undetected, indicating little dust content of
$<3.9\times10^{6}\,M_\odot\,(3\sigma)$, and we obtained a more stringent
constraint on the total infrared luminosity. We updated the [O III]/[C II]
luminosity ratios to $10.2\pm4.7~(6.1\pm3.5$) and $20\pm12~(9.6\pm6.1$) for
$4.5\sigma$ and $3.6\sigma$ [C II] detections, respectively, where the ratios
in the parentheses are corrected for the surface brightness dimming effect on
the extended [C II] emission. We also found a strong [C II] deficit ($0.6-1.3$
dex) between SXDF-NB1006-2 and the mean $L_{\rm{[CII]}}-\rm{SFR}$ relation of
galaxies at $0
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present a set of multi-wavelength mosaics and photometric catalogs in the ALMA lensing cluster survey (ALCS) fields. The catalogs were built by reprocessing of archival data from the CHArGE compilation, taken by the $\textit{Hubble Space Telescope}$ ($\textit{HST}$) in the RELICS, CLASH and Hubble Frontier Fields. Additionally we have reconstructed the $\textit{Spitzer}$ IRAC 3.6 and 4.5 $\mu$m mosaics, by utilising all the available archival IRSA/SHA exposures. To alleviate the effect of blending in such a crowded region, we have modelled the $\textit{Spitzer}$ photometry by convolving the $\textit{HST}$ detection image with the $\textit{Spitzer}$ PSF using the novel $\texttt{golfir}$ software. The final catalogs contain 218,000 sources, covering a combined area of 690 arcmin$^2$. These catalogs will serve as an important tool in aiding the search of the sub-mm galaxies in future ALMA surveys, as well as follow ups of the $\textit{HST}$ dark - IRAC sources. Coupled with the available $\textit{HST}$ photometry the addition of the 3.6 and 4.5 $\mu$m bands will allow us to place a better constraint on photometric redshifts and stellar masses of these objects, thus giving us an opportunity to identify high-redshift candidates for spectroscopic follow ups and answer the important questions regarding the epoch of reionization and formation of first galaxies.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report the physical characterization of four CO emitters detected near the bright submillimeter galaxy (SMG) SSA22-AzTEC26. We analyze the data from ALMA band 3, 4, and 7 observations of the SSA22-AzTEC26 field. In addition to the targeted SMG, we detect four line emitters with SNR$>5.2$ in the cube smoothed with 300 km s$^{-1}$ FWHM Gaussian filter. All four sources have near-infrared (NIR) counterparts within 1 arcsec. We perform ultraviolet to far-infrared spectral energy distribution (SED) modeling to derive the photometric redshift and physical properties. Based on photometric redshift, we reveal that two of them are CO(2-1) at a redshift of 1.113 and 1.146, and one is CO(3-2) at $z=2.124$. The three sources are massive galaxies with a stellar mass $\gtrsim10^{10.5}M_\odot$, but have different levels of star formation. Two lie within the scatter of the main sequence (MS) of star-forming galaxies at $z\sim1-2$, and the most massive galaxy lies significantly below the MS. However, all three sources have a gas fraction within the scatter of the MS scaling relation. This shows that a blind CO line search can detect massive galaxies with low specific star formation rates that still host large gas reservoirs and complements targeted surveys, suggesting later gas acquisition and the need for other mechanisms in addition to gas consumption to suppress the star formation.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Integrated superconducting spectrometer (ISS) technology will enable ultra-wideband, integral-field spectroscopy for (sub)millimeter-wave astronomy, in particular, for uncovering the dust-obscured cosmic star formation and galaxy evolution over cosmic time. Here we present the development of DESHIMA 2.0, an ISS for ultra-wideband spectroscopy toward high-redshift galaxies. DESHIMA 2.0 is designed to observe the 220-440 GHz band in a single shot, corresponding to a redshift range of $z$=3.3-7.6 for the ionized carbon emission ([C II] 158 $\mu$m). The first-light experiment of DESHIMA 1.0, using the 332-377 GHz band, has shown an excellent agreement among the on-sky measurements, the lab measurements, and the design. As a successor to DESHIMA 1.0, we plan the commissioning and the scientific observation campaign of DESHIMA 2.0 on the ASTE 10-m telescope in 2023. Ongoing upgrades for the full octave-bandwidth system include the wideband 347-channel chip design and the wideband quasi-optical system. For efficient measurements, we also develop the observation strategy using the mechanical fast sky-position chopper and the sky-noise removal technique based on a novel data-scientific approach. In the paper, we show the recent status of the upgrades and the plans for the scientific observation campaign.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: High-resolution observations of ionized and molecular gas in the nuclear regions of galaxies are indispensable for delineating the interplay of star formation, gaseous inflows, stellar radiation, and feedback processes. Combining our new ALMA band 3 mapping and archival VLT/MUSE data, we present a spatially resolved analysis of molecular and ionized gas in the central 5.4 Kpc region of NGC 1365. We find the star formation rate/efficiency (SFR/SFE) in the inner circumnuclear ring is about 0.4/1.1 dex higher than in the outer regions. At a linear resolution of 180 pc, we obtain a super-linear Kennicutt-Schmidt law, demonstrating a steeper slope (1.96$\pm$0.14) than previous results presumably based on lower-resolution observations. Compared to the northeastern counterpart, the southwestern dust lane shows lower SFE, but denser molecular gas, and larger virial parameters. This is consistent with an interpretation of negative feedback from AGN and/or starburst, in the sense that the radiation/winds can heat and interact with the molecular gas even in relatively dense regions. After subtracting the circular motion component of the molecular gas and the stellar rotation, we detect two prominent non-circular motion components of molecular and ionized hydrogen gas, reaching a line-of-sight velocity of up to 100 km/s. We conclude that the winds or shocked gas from the central AGN may expel the low-density molecular gas and diffuse ionized gas on the surface of the rotating disk.