arXiv subjects

Junfeng Wang

Publications and source records attributed to Junfeng Wang.

At least 127 records · Page 7Linked to original sources

arXiv2022

Fast Outflowing Warm Absorbers in Narrow-Line Seyfert 1 Galaxy PG 1001+054 Revealed by HST/COS Spectra

Narrow-Line Seyfert 1 (NLS1) Galaxies are an important type of active galactic nucleus (AGN), generally expected to be accreting at high Eddington rate. The properties of their outflows and importance of AGN feedback remain intriguing. We report on the discovery of fast outflowing warm absorbers (WAs) in the NLS1 PG 1001+054, with velocities in the range of 7000 to 9000 kilometers per second. They are identified with blueshifted Lyman alpha, N v and Si iv lines in the high resolution ultraviolet (UV) spectra taken with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST). We perform photoionization modeling using XSTAR with three WAs. The derived physical properties are typical of WAs in terms of ionization and column density, whereas the outflow velocities are significantly higher. The estimated location of these WAs ranges from 1 to 73 parsecs away from the AGN. Together with previous detection of high ionization absorber in the X-ray for PG 1001+054, we suggest that the fast outflowing UV absorber is probably a part of a multiphase outflow. Such structure is likely produced by the outflow launched from AGN at accretion disk scale, which shocks the ambient ISM producing stratified absorbers. Assuming contribution from the three WAs at tens of parsecs, the estimated ratio between the kinetic power of the outflow and AGN Eddington luminosity could reach 1.7 percent, raising the possibility of sufficient influence on the host galaxy when compared to some theoretical models for efficient AGN feedback.

astro-ph.GA↗

arXiv2022

On the Hadronic Origin of High Energy Emission of $γ$-ray Loud Narrow-Line Seyfert 1 PKS 1502+036

The radiation mechanism of Radio-Loud Narrow-Line Seyfert 1 (RL-NLS1) from X-ray to $γ$-ray bands remains an open question. While the leptonic model has been employed to explain the spectral energy distribution (SED), the hadronic process may potentially account for the high energy radiation of some $γ$-ray loud Narrow-Line Seyfert 1 (NLS1) as well. We study one of such RL-NLS1, PKS 1502+036, comparing the theoretical SEDs predicted by the leptonic model and the lepto-hadronic model to the observed one. For the hadronic processes, we take into account the proton synchrotron radiation and proton-photon interactions (including the Bethe-Heitler process and the photopion process) including the emission of pairs generated in the electromagnetic cascade initiated by these processes. Our results show that the leptonic model can reproduce the SED of this source, in which the X-ray to $γ$-ray radiation can be interpreted as the inverse Compton (IC) scattering. On the other hand, the proton synchrotron radiation can also explain the high energy component of SED although extreme parameters are needed. We also demonstrate that the $pγ$ interactions as well as the cascade process cannot explain SED. Our results imply that a leptonic origin is favored for the multi-wavelength emission of PKS 1502+036.

astro-ph.HE↗

arXiv2022

The Unusual AGN Host NGC 1266: Evidence for Shocks in a Molecular Gas Rich S0 Galaxy with a Low Luminosity Nucleus

NGC 1266 is a lenticular galaxy (S0) hosting an active galactic nucleus (AGN), and known to contain a large amount of shocked gas. We compare the luminosity ratio of mid-\emph{J} CO lines to IR continuum with star-forming galaxies (SFGs), and then model the CO spectral line energy distribution (SLED). We confirm that in the mid- and high-\emph{J} regions ($J_{\rm up}$ = 4--13), the C-type shock ($v_{\rm s}$ = 25 km s$^{-1}$, $n_{\rm H}$ = $5\times10^{4}$ cm$^{-3}$) can reproduce the CO observations well. The galaxy spectral energy distribution (SED) is constructed and modeled by the code {\tt X-CIGALE} and obtains a set of physical parameters including the star formation rate (SFR, 1.17 $\pm$ 0.47 \emph{M$_{\odot}$}yr$^{-1}$). Also, our work provides SFR derivation of [C\,{\sc ii}] from the neutral hydrogen regions only (1.38 $\pm$ 0.14 $M_{\odot}$yr$^{-1}$). Previous studies have illusive conclusions on the AGN or starburst nature of the NGC 1266 nucleus. Our SED model shows that the hidden AGN in the system is intrinsically low-luminosity, consequently the infrared luminosity of the AGN does not reach the expected level. Archival data from \emph{NuSTAR} hard X-ray observations in the 3--79 keV band shows a marginal detection, disfavoring presence of an obscured luminous AGN and implying that a compact starburst is more likely dominant for the NGC 1266 nucleus.

astro-ph.GA↗

arXiv2022

The Disk Population in a Distant Massive Protocluster

The unprecedented angular resolution and sensitivity of ALMA makes it possible to unveil disk populations in distant ($>$2 kpc), embedded young cluster environments. We have conducted an observation towards the central region of the massive protocluster G286.21+0.16 at 1.3 mm. With a spatial resolution of 23 mas and a sensitivity of 15 $\rm μJy~beam^{-1}$, we detect a total of 38 protostellar disks. These disks have dust masses ranging from about 53 to 1825 $M_\oplus$, assuming a dust temperature of 20 K. This sample is not closely associated with previously identified dense cores, as would be expected for disks around Class 0 protostars. Thus, we expect our sample, being flux limited, to be mainly composed of Class I/flat-spectrum source disks, since these are typically more massive than Class II disks. Furthermore, we find that the distributions of disk masses and radii are statistically indistinguishable with those of the Class I/flat-spectrum objects in the Orion molecular cloud, indicating similar processes are operating in G286.21+0.16 to regulate disk formation and evolution. The cluster center appears to host a massive protostellar system composed of three sources within 1200 au, including a potential binary with 600 au projected separation. Relative to this center, there is no evidence for widespread mass segregation in the disk population. We do find a tentative trend of increasing disk radius versus distance from the cluster center, which may point to the influence of dynamical interactions being stronger in the central regions.

astro-ph.GA↗

arXiv2022

A long-period pre-ELM system discovered from LAMOST medium-resolution survey

We present LAMOST~J041920.07+072545.4 (hereafter J0419), a close binary consisting of a bloated extremely low mass pre-white dwarf (pre-ELM WD) and a compact object with an orbital period of 0.607189~days. The large-amplitude ellipsoidal variations and the evident Balmer and He~I emission lines suggest a filled Roche lobe and ongoing mass transfer. No outburst events were detected in the 15 years of monitoring of J0419, indicating a very low mass transfer rate. The temperature of the pre-ELM, $T_\mathrm{eff} = 5793_{-133}^{+124}\,\rm K$, is cooler than the known ELMs, but hotter than most CV donors. Combining the mean density within the Roche lobe and the radius constrained from our SED fitting, we obtain the mass of the pre-ELM, $M_1 = 0.176\pm 0.014\,M_\odot$. The joint fitting of light and radial velocity curves yields an inclination angle of $i = 66.5_{-1.7}^{+1.4}$ degrees, corresponding to the compact object mass of $M_2 = 1.09\pm 0.05\,M_\odot$. The very bloated pre-ELM has a smaller surface gravity ($\log g = 3.9\pm 0.01$, $R_1 = 0.78 \pm 0.02\,R_\odot$) than the known ELMs or pre-ELMs. The temperature and the luminosity ($L_\mathrm{bol} = 0.62_{-0.10}^{+0.11}\,L_\odot$) of J0419 are close to the main sequence, which makes the selection of such systems through the HR diagram inefficient. Based on the evolutionary model, the relatively long period and small $\log g$ indicate that J0419 could be close to the "bifurcation period" in the orbit evolution, which makes J0419 to be a unique source to connect ELM/pre-ELM WD systems, wide binaries and cataclysmic variables.

astro-ph.SR↗

arXiv2022

A White Dwarf-Main Sequence Binary Unveiled by Time-Domain Observations from LAMOST and TESS

We report a single-lined white dwarf-main sequence binary system, LAMOST J172900.17+652952.8, which is discovered by LAMOST's medium resolution time-domain surveys. The radial velocity semi-amplitude and orbital period of the optical visible star are measured by using the Palomar 200-inch telescope follow-up observations and the light curves from TESS. Thus the mass function of the invisible candidate white dwarf is derived, $f(M_{\rm{2}}) = 0.120\,\pm\,0.003\,M_{\odot}$. The mass of the visible star is measured based on the spectral energy distribution fitting, $M_{\mathrm{1}}$ = $0.81^{+0.07}_{-0.06}\,M_{\odot}$. Hence, the mass of its invisible companion is $M_{\rm{2}}\,\gtrsim\,0.63\,M_{\odot}$. The companion ought to be a compact object rather than a main-sequence star owing to the mass ratio $q = M_{\rm{2}} / M_{\rm 1} \gtrsim 0.78$ and the single-lined spectra. The compact object is likely to be a white dwarf except for small inclination angle, $i\,\lesssim\,40^{\circ}$. By using the GALEX NUV flux, the effective temperature of the white dwarf candidate is constrained as $T_{\rm eff}^{\rm WD}\,\lesssim\,12000-13500$ K. It is difficult to detect white dwarfs which are outshone by their bright companions via single-epoch optical spectroscopic surveys. Therefore, the optical time-domain surveys can play an important role in unveiling invisible white dwarfs and other compact objects in binaries.

astro-ph.SR↗

arXiv2022

A dynamically discovered and characterized non-accreting neutron star -- M dwarf binary candidate

Optical time-domain surveys can unveil and characterize exciting but less-explored non-accreting and/or non-beaming neutron stars (NS) in binaries. Here we report the discovery of such a NS candidate using the LAMOST spectroscopic survey. The candidate, designated LAMOST J112306.9+400736 (hereafter J1123), is in a single-lined spectroscopic binary containing an optically visible M star. The star's large radial velocity variation and ellipsoidal variations indicate a relatively massive unseen companion. Utilizing follow-up spectroscopy from the Palomar 200-inch telescope and high-precision photometry from TESS, we measure a companion mass of $1.24_{-0.03}^{+0.03}~M_{\odot}$. Main-sequence stars with this mass are ruled out, leaving a NS or a massive white dwarf (WD). Although a massive WD cannot be ruled out, the lack of UV excess radiation from the companion supports the NS hypothesis. Deep radio observations with FAST yielded no detections of either pulsed or persistent emission. J1123 is not detected in numerous X-ray and gamma-ray surveys. These non-detections suggest that the NS candidate is not presently accreting and pulsing. Our work exemplifies the capability of discovering compact objects in non-accreting close binaries by synergizing the optical time-domain spectroscopy and high-cadence photometry.

astro-ph.SR↗

arXiv2022

Revisit the Circumnuclear X-ray Emission of NGC 2992 in a Historically Low State

The inner-most region of the Seyfert galaxy NGC 2992 has long been suspected to be the location of intense AGN-host galaxy interaction, but photon pile-up in previous high-resolution observations hampered the study of soft X-ray excess and the interaction near its nucleus. We present an X-ray imaging spectroscopic analysis of the circumnuclear ($1^{\prime\prime}$--$3^{\prime\prime}$) region of NGC 2992 using the zeroth-order image of a 135 ks grating observation obtained with Chandra, which captured the nucleus in a historically low flux state. Extended soft X-ray emission is detected in the circumnuclear region with observed luminosity $L_{\rm X} \sim 7 \times 10^{39}\rm\ erg\ s^{-1}$. The majority of previously puzzling detection of soft excess could be associated with the outflow, indicated by the morphological correspondences between soft X-ray emission and figure-eight-shaped radio bubbles. An anomalous narrow emission line with the centroid energy $\sim4.97$ keV is found. If attributed to redshifted highly ionized iron emission (e.g., Fe xxv), the required outflow velocity is $\sim0.23\,c$. An alternative explanation is that this line emission could be produced by the nuclear spallation of iron. We also find asymmetric extended Fe K$α$ emission along the galactic disk, which could originate from reflection by cold gas on $\sim 200$ pc scale.

astro-ph.GA↗

arXiv2022

MaNGA 8313-1901: gas accretion observed in a blue compact dwarf galaxy?

Gas accretion is an important process in the evolution of galaxies, but it has limited direct observational evidences. In this paper, we report the detection of a possible ongoing gas accretion event in a Blue Compact Dwarf (BCD) galaxy, MaNGA 8313-1901, observed by the Mapping Nearby Galaxies and Apache Point Observatory (MaNGA) program. This galaxy has a distinct off-centered blue clump to the northeast (the NE clump) that shows low metallicity and enhanced star-formation. The kinematics of the gas in the NE clump also seems to be detached from the host BCD galaxy. Together with the metallicity drop of the NE clump, it suggests that the NE clump likely has an external origin, such as the gas accretion or galaxy interaction, rather than an internal origin, such as an \hii~complex in the disk. After removing the underlying host component, we find that the spectrum of the "pure" clump can match very well with a modeled spectrum containing a stellar population of the young stars ($\le 7$ Myr) only. This may imply that the galaxy is experiencing an accretion of cold gas, instead of a merger event involving galaxies with significant pre-existing old stars. We also find signs of another clump (the SW clump) at the south-west corner of the host galaxy, and the two clumps may share the same origin of gas accretion.

astro-ph.GA↗

arXiv2022

Multiple and Asymmetric Scalings in Explosive Percolation

Explosive percolation in the Achlioptas process has recently attracted much research attention. From extensive simulations in an event-based ensemble, we find that, in dimensions from $2$ to $6$ and on random graphs, the Achlioptas processes all have two scaling windows and multiple fractal structures. The mixing of these multiple scalings successfully explains the previously observed anomalous phenomena in the conventional ensemble, and, moreover, correct critical exponents are now determined with a high precision by the event-based method. The multiple scalings and the ensemble inequivalence may bring new insights for other statistical systems.

cond-mat.stat-mech↗

arXiv2022

Repeating Ultraluminous X-ray Bursts and Repeating Fast Radio Bursts: A Possible Association?

Ultraluminous X-ray bursts (hereafter ULXBs) are ultraluminous X-ray flares with a fast rise ($\sim$ one minute) and a slow decay ($\sim$ an hour), which are commonly observed in extragalactic globular clusters. Most ULXBs are observational one-off bursts, whereas five flares from the same source in NGC 5128 were discovered by Irwin et al. (2016). In this Letter, we propose a neutron star (NS)-white dwarf (WD) binary model with super-Eddington accretion rates to explain the repeating behavior of the ULXB source in NGC 5128. With an eccentric orbit, the mass transfer occurs at the periastron where the WD fills its Roche lobe. The ultraluminous X-ray flares can be produced by the accretion column around the NS magnetic poles. On the other hand, some repeating fast radio bursts (hereafter FRBs) were also found in extragalactic globular clusters. Repeating ULXBs and repeating FRBs are the most violent bursts in the X-ray and radio bands, respectively. We propose a possible association between the repeating ULXBs and the repeating FRBs. Such an association is worth further investigation by follow-up observations on nearby extragalactic globular clusters.

astro-ph.HE↗

arXiv2022

Possible coexistence of short-range resonating-valence-bond and long-range stripe correlations in the spatially anisotropic triangular-lattice quantum magnet Cu$_2$(OH)$_3$NO$_3$

We show that short-range resonating-valence-bond correlations and long-range order can coexist in the ground state (GS) of a frustrated spin system. Our study comprises a comprehensive investigation of the quantum magnetism on the structurally disorder-free single crystal of Cu$_2$(OH)$_3$NO$_3$, which realizes the $s$ = 1/2 Heisenberg model on a spatially anisotropic triangular lattice. Competing exchange interactions determined by fitting the magnetization measured up to 55 T give rise to an exotic GS wavefunction with coexistence of the dominant short-range resonating-valence-bond correlations and weak long-range stripe order (ordered moment $M_0$ = $|\langle s_i^z\rangle|$ $\sim$ 0.02). At low temperatures, a first-order spin-flop transition is visible at $\sim$ 1-3 T. As the applied field further increases, another two magnetic-field-induced quantum phase transitions are observed at $\sim$ 14-19 and $\sim$ 46-52 T, respectively. Simulations of the Heisenberg exchange model show semi-quantitative agreement with the magnetic-field modulation of these unconventional phases, as well as the absence of visible magnetic reflections in neutron diffraction, thus supporting the GS of the spin system of Cu$_2$(OH)$_3$NO$_3$ may be approximate to a quantum spin liquid. Our study establishes structurally disorder-free magnetic materials with spatially anisotropic exchange interactions as a possible arena for spin liquids.

cond-mat.str-el↗

arXiv2022

Spatially Resolved Ionized Outflows Extending to $\sim$2 kpc in Seyfert 1 Galaxy NGC 7469 Revealed by VLT/MUSE

The Seyfert 1 galaxy NGC 7469 possesses a prominent nuclear starburst ring and a luminous active galactic nucleus (AGN). Evidence of an outflow in the innermost nuclear region has been found in previous works. We detect the ionized gas outflow on a larger scale in the galaxy using the archival VLT/MUSE and {\em Chandra} observations. The optical emission lines are modeled using two Gaussian components, and a non-parametric approach is applied to measure the kinematics of [O III] and $\rm Hα$ emitting gas. Line ratio diagnostics and spatially resolved maps are derived to examine the origin of the outflow. The kpc-scale kinematics of [O III] is dominated by a blueshifted component whereas velocity map of $\rm Hα$ shows a rotational disk with complex non-rotational substructure. The starburst wind around the circumnuclear ring is confirmed, and we find evidence of an AGN-driven outflow extending to a radial distance of $\rm \sim2$ kpc from the nucleus, with a morphology consistent with a nearly face-on ionization cone. The previously reported circumnuclear outflow resembles part of the bright base. We derive mass and energy outflow rates for both the starburst wind and the AGN-driven outflow. The estimated kinetic coupling efficiency of the kpc-scale AGN outflow is $\dot{E}_{\rm out}/L_{\rm bol}\sim 0.1\%$, lower than the threshold predicted by the ``two-stage'' theoretical model for effective feedback. Our results reinforce the importance of spatially resolved study to disentangle feedback where AGN and starburst coexist, which may be common during the cosmic noon of black hole and galaxy growth.

astro-ph.GA↗

arXiv2022

X-ray emission of contact binary variables within 1 kpc

By assembling the largest sample to date of X-ray emitting EW-type binaries (EWXs), we carried out correlation analyses for the X-ray luminosity log$L_{\textrm{X}}$, and X-ray activity level log($L_{\textrm{X}}$/$L_{\textrm{bol}}$) versus the orbital period $P$ and effective temperature $T_{\rm eff}$. We find strong $P$-log$L_{\textrm{X}}$ and $P$-log($L_{\textrm{X}}$/$L_{\textrm{bol}}$) correlations for EWXs with $P$ < 0.44 days and we provide the linear parametrizations for these relations, on the basis of which the orbital period can be treated as a good predictor for log$L_{\textrm{X}}$ and log($L_{\textrm{X}}$/$L_{\textrm{bol}}$). The aforementioned binary stellar parameters are all correlated with log$L_{\textrm{X}}$, while only $T_{\rm eff}$ exhibits a strong correlation with log($L_{\textrm{X}}$/$L_{\textrm{bol}}$). Then, EWXs with higher temperature show lower X-ray activity level, which could indicate the thinning of the convective area related to the magnetic dynamo mechanism. The total X-ray luminosity of an EWX is essentially consistent with that of an X-ray saturated main sequence star with the same mass as its primary, which may imply that the primary star dominates the X-ray emission. The monotonically decreasing $P$-log($L_{\textrm{X}}$/$L_{\textrm{bol}}$) relation and the short orbital periods indicate that EWXs could all be in the X-ray saturated state, and they may inherit the changing trend of the saturated X-ray luminosities along with the mass shown by single stars. For EWXs, the orbital period, mass, and effective temperature increase in concordance. We demonstrate that the period $P=0.44$ days corresponds to the primary mass of $\sim1.1 \rm M_\odot$, beyond which the saturated X-ray luminosity of single stars will not continue to increase with mass. This explains the break in the positive $P$-log$L_{\textrm{X}}$ relation for EWXs with $P>0.44$ days.

astro-ph.HE↗

arXiv2022

Iterative Self-consistent Parallel Magnetic Resonance Imaging Reconstruction based on Nonlocal Low-Rank Regularization

Iterative self-consistent parallel imaging reconstruction (SPIRiT) is an effective self-calibrated reconstruction model for parallel magnetic resonance imaging (PMRI). The joint L1 norm of wavelet coefficients and joint total variation (TV) regularization terms are incorporated into the SPIRiT model to improve the reconstruction performance. The simultaneous two-directional low-rankness (STDLR) in k-space data is incorporated into SPIRiT to realize improved reconstruction. Recent methods have exploited the nonlocal self-similarity (NSS) of images by imposing nonlocal low-rankness of similar patches to achieve a superior performance. To fully utilize both the NSS in Magnetic resonance (MR) images and calibration consistency in the k-space domain, we propose a nonlocal low-rank (NLR)-SPIRiT model by incorporating NLR regularization into the SPIRiT model. We apply the weighted nuclear norm (WNN) as a surrogate of the rank and employ the Nash equilibrium (NE) formulation and alternating direction method of multipliers (ADMM) to efficiently solve the NLR-SPIRiT model. The experimental results demonstrate the superior performance of NLR-SPIRiT over the state-of-the-art methods via three objective metrics and visual comparison.

eess.IV↗

arXiv2021

Percolation thresholds of randomly rotating patchy particles on Archimedean lattices

We study the percolation of randomly rotating patchy particles on $11$ Archimedean lattices in two dimensions. Each vertex of the lattice is occupied by a particle, and in each model the patch size and number are monodisperse. When there are more than one patches on the surface of a particle, they are symmetrically decorated. As the proportion $χ$ of the particle surface covered by the patches increases, the clusters connected by the patches grow and the system percolates at the threshold $χ_c$. We combine Monte Carlo simulations and the critical polynomial method to give precise estimates of $χ_c$ for disks with one to six patches and spheres with one to two patches on the $11$ lattices. For one-patch particles, we find that the order of $χ_c$ values for particles on different lattices is the same as that of threshold values $p_c$ for site percolation on same lattices, which implies that $χ_c$ for one-patch particles mainly depends on the geometry of lattices. For particles with more patches, symmetry become very important in determining $χ_c$. With the estimates of $χ_c$ for disks with one to six patches, by analyses related to symmetry, we are able to give precise values of $χ_c$ for disks with an arbitrary number of patches on all $11$ lattices. The following rules are found for patchy disks on each of these lattices: (i) as the number of patches $n$ increases, values of $χ_c$ repeat in a periodic way, with the period $n_0$ determined by the symmetry of the lattice; (ii) when $\mod(n,n_0)=0$, the minimum threshold value $χ_{\rm min}$ appears, and the model is equivalent to site percolation with $χ_{\rm min}=p_c$; (iii) disks with $\mod(n,n_0)=m$ and $n_0-m$ ($m<n_0/2$) share the same $χ_c$ value.

cond-mat.stat-mech↗

arXiv2021

The Disk Veiling Effect of the Black Hole Low-Mass X-ray Binary A0620-00

The optical light curves of quiescent black hole low-mass X-ray binaries often exhibit significant non-ellipsoidal variabilities, showing the photospheric radiation of the companion star is veiled by other source of optical emission. Assessing this "veiling" effect is critical to the black hole mass measurement. Here in this work, we carry out a strictly simultaneous spectroscopic and photometric campaign on the prototype of black hole low-mass X-ray binary A0620-00. We find that for each observation epoch, the extra optical flux beyond a pure ellipsoidal modulation is positively correlated with the fraction of veiling emission, indicating the accretion disk contributes most of the non-ellipsoidal variations. Meanwhile, we also obtain a K2V spectral classification of the companion, as well as the measurements of the companion's rotational velocity $v \sin i = 83.8\pm1.9$ km s$^{-1}$ and the mass ratio between the companion and the black hole $q=0.063\pm0.004$.

astro-ph.HE↗

arXiv2021

The HASHTAG project: The First Submillimeter Images of the Andromeda Galaxy from the Ground

Observing nearby galaxies with submillimeter telescopes on the ground has two major challenges. First, the brightness is significantly reduced at long submillimeter wavelengths compared to the brightness at the peak of the dust emission. Second, it is necessary to use a high-pass spatial filter to remove atmospheric noise on large angular scales, which has the unwelcome by-product of also removing the galaxy's large-scale structure. We have developed a technique for producing high-resolution submillimeter images of galaxies of large angular size by using the telescope on the ground to determine the small-scale structure (the large Fourier components) and a space telescope (Herschel or Planck) to determine the large-scale structure (the small Fourier components). Using this technique, we are carrying out the HARP and SCUBA-2 High Resolution Terahertz Andromeda Galaxy Survey (HASHTAG), an international Large Program on the James Clerk Maxwell Telescope, with one aim being to produce the first high-fidelity high-resolution submillimeter images of Andromeda. In this paper, we describe the survey, the method we have developed for combining the space-based and ground-based data, and present the first HASHTAG images of Andromeda at 450 and 850um. We also have created a method to predict the CO(J=3-2) line flux across M31, which contaminates the 850um band. We find that while normally the contamination is below our sensitivity limit, the contamination can be significant (up to 28%) in a few of the brightest regions of the 10 kpc ring. We therefore also provide images with the predicted line emission removed.

astro-ph.GA↗