Hα Excess Research Articles

Very Extended Ionized Gas Discovered around NGC 1068 with the Circumgalactic Hα Spectrograph

We have performed wide-field, ultra-low-surface-brightness Hα emission-line mapping around NGC 1068 with the newly commissioned Circumgalactic Hα Spectrograph. NGC 1068 is notable for its active galactic nucleus, which globally ionizes gas in the disk and halo. Line-emitting diffuse ionized gas is distributed throughout the galactic disk and large-scale ionized filaments are found well beyond the disk, aligned with the cone angle of the central jet. We report the discovery of a new ribbon of ionized gas around NGC 1068 beyond even the known outer filamentary structure, located 20 kpc from the galaxy. The Hα surface brightness of this ribbon is on the order of the bright telluric lines, ranging from 4 to 16 R, with fainter regions on the order of the sky background continuum. Unlike previous extended emission, the ribbon is not as well aligned with the current axis of the central jet. It is not associated with any galactic structure or known tidal features in the halo of NGC 1068, though it may originate from a larger distribution of unmapped neutral atomic or molecular gas in the halo. The morphology of the ribbon emission in Hα is correlated with extended UV emission around NGC 1068. Hα-to-UV flux ratios in the ribbon are comparable to extended emission-line ratios in the halos of NGC 5128, NGC 253, and M82. The Hα excess in the ribbon gas suggests ionization by slow shocks or a mixture of in situ star formation and photoionization and collisional ionization processes.

Photometric determination of the mass accretion rates of pre-main-sequence stars

Aims. We study the properties of low-mass stars recently formed in the field of the NGC 376 cluster in the Small Magellanic Cloud (SMC). Methods. Using photometric observations acquired with the Hubble Space Telescope (HST) in the V, I, and Hα bands, we identify 244 candidate pre-main-sequence (PMS) stars showing Hα excess emission at the 5σ level and with Hα equivalent width of 20 Å or more. We derive physical parameters for all PMS stars, including masses, ages, and mass accretion rates. We compare the effective mass accretion rate of stars in NGC 376 to that of objects in the NGC 346 cluster, with NGC 346 featuring similar metallicity but higher total mass and gas density. Results. We find a median age of 28 Myr for this population (with 25th and 75th percentiles at about 20 and 40 Myr, respectively), in excellent agreement with previous studies of massive stars in the same field. The PMS stars are rather uniformly distributed across the field, whereas massive stars are more clustered. The spatial distribution of PMS objects is compatible with them having formed in the centre of the cluster and then migrating outwards. We find that in NGC 376 the mass accretion rate is systematically lower than in NGC 346 for stars of the same mass and age. This indicates that, in addition to metallicity, there are other environmental factors affecting the rate of mass accretion onto PMS stars. Our observations suggest that the gas density in the star-forming region might play a role.

Photometric determination of the mass accretion rates of pre-main-sequence stars

We studied the properties of the young stellar populations in the NGC 299 cluster in the Small Magellanic Cloud using observations obtained with the Hubble Space Telescope in the V, I, and Hα bands. We identified 250 stars with Hα excess exceeding 5σ and an equivalent width of the Hα emission line of at least 20 Å, which indicates that these stars are still undergoing active accretion and therefore represent bona fide pre-main-sequence (PMS) objects. For 240 of them, we derived physical stellar parameters such as the mass, age, and mass accretion rate by comparing the observed photometry with theoretical models. We find evidence that suggests the existence of two populations of PMS stars, one with a median age of around 25 Myr and the other about 50 Myr old. These ages are consistent with previously determined ages for the main population of the cluster. The average mass accretion rate for these PMS stars is ∼5 × 10−9 M⊙ yr−1, which is comparable to the values found with the same method in other low-metallicity, low-density clusters in the Magellanic Clouds, but is about a factor of three lower than those measured for stars of similar mass and age in denser Magellanic Cloud stellar regions. Our findings support the hypothesis that both the metallicity and density of the forming environment can affect the mass accretion rate and thus the star formation process in a region. A study of the spatial distribution of both massive stars and (low-mass) PMS objects reveals that the former are clustered near the nominal centre of NGC 299, whereas the PMS stars are rather uniformly distributed over the field. Although it is possible that the PMS stars formed in situ in a more diffuse manner than massive stars, it is also plausible that the PMS stars formed initially in a more compact structure together with the massive stars and were later dispersed due to two-body relaxation. To explore this possibility, we studied the cluster’s stellar density profile. We find a core radius rc ≃ 0.6 pc and a tidal radius rt ≃ 5.5 pc, with an implied concentration parameter c ≃ 1, suggesting that the cluster could be dispersing into the field.

Exotica in the globular cluster M4, studied with Chandra, HST, and the VLA

ABSTRACT Using the Hubble Ultraviolet Globular Cluster Survey (HUGS) and additional HST archival data, we have carried out a search for optical counterparts to the low-luminosity Chandra X-ray sources in the globular cluster M4 (NGC 6121). We have also searched for optical or X-ray counterparts to radio sources detected by the VLA. We find 24 new confident optical counterparts to Chandra sources for a total of 40, including the 16 previously identified. Of the 24 new identifications, 18 are stellar coronal X-ray sources (active binaries, ABs), the majority located along the binary sequence in a V606–I814 colour–magnitude diagram and generally showing an H α excess. In addition to confirming the previously detected cataclysmic variable (CV, CX4), we identify one confident new CV (CX76), and two candidates (CX81 and CX101). One MSP is known in M4 (CX12), and another strong candidate has been suggested (CX1); we identify some possible MSP candidates among optical and radio sources, such as VLA20, which appears to have a white dwarf counterpart. One X-ray source with a sub-subgiant optical counterpart and a flat radio spectrum (CX8, VLA31) is particularly mysterious. The radial distribution of X-ray sources suggests a relaxed population of average mass $\sim 1.2\!-\! 1.5\, \mbox{$\mathrm{ M_\odot} $}$. Comparing the numbers of ABs, MSPs, and CVs in M4 with other clusters indicates that AB numbers are proportional to cluster mass (primordial population), MSPs to stellar encounter rate (dynamically formed population), while CVs seem to be produced both primordially and dynamically.

A naive Bayes classifier for identifying Class II YSOs

ABSTRACTA naive Bayes classifier for identifying Class II YSOs has been constructed and applied to a region of the Northern Galactic Plane containing 8 million sources with good quality Gaia EDR3 parallaxes. The classifier uses the five features: Gaia G-band variability, WISE mid-infrared excess, UKIDSS and 2MASS near-infrared excess, IGAPS Hα excess, and overluminosity with respect to the main sequence. A list of candidate Class II YSOs is obtained by choosing a posterior threshold appropriate to the task at hand, balancing the competing demands of completeness and purity. At a threshold posterior greater than 0.5, our classifier identifies 6504 candidate Class II YSOs. At this threshold, we find a false positive rate around 0.02 per cent and a true positive rate of approximately 87 per cent for identifying Class II YSOs. The ROC curve rises rapidly to almost one with an area under the curve around 0.998 or better, indicating the classifier is efficient at identifying candidate Class II YSOs. Our map of these candidates shows what are potentially three previously undiscovered clusters or associations. When comparing our results to published catalogues from other young star classifiers, we find between one quarter and three quarters of high probability candidates are unique to each classifier, telling us no single classifier is finding all young stars.

Spectroscopic follow-up of a subset of the Gaia/IPHAS catalogue of Hα-excess sources

ABSTRACT State-of-the-art techniques to identify Hα emission-line sources in narrow-band photometric surveys consist of searching for Hα excess with reference to nearby objects in the sky (position-based selection). However, while this approach usually yields very few spurious detections, it may fail to select intrinsically faint and/or rare Hα-excess sources. In order to obtain a more complete representation of the heterogeneous emission-line populations, we recently developed a technique to find outliers relative to nearby objects in the colour–magnitude diagram (CMD-based selection). By combining position-based and CMD-based selections, we built an updated catalogue of Hα-excess candidates in the Northern Galactic Plane. Here, we present spectroscopic follow-up observations and classification of 114 objects from this catalogue that enables us to test our novel selection method. Out of the 70 spectroscopically confirmed Hα-emitters in our sample, 15 were identified only by the CMD-based selection, and would have been thus missed by the classic position-based technique. In addition, we explore the distribution of our spectroscopically confirmed emitters in the Gaia CMD. This information can support the classification of emission-line sources in large surveys such as the upcoming WEAVE and 4-m Multi-Object Spectroscopic Telescope, especially if augmented with the introduction of other colours.

Improved Orbital Constraints and Hα Photometric Monitoring of the Directly Imaged Protoplanet Analog HD 142527 B

Companions embedded in the cavities of transitional circumstellar disks have been observed to exhibit excess luminosity at Hα, an indication that they are actively accreting. We report 5 yr (2013–2018) of monitoring of the position and Hα excess luminosity of the embedded, accreting low-mass stellar companion HD 142527 B from the MagAO/VisAO instrument. We use pyklip, a Python implementation of the Karhunen–Loeve Image Processing algorithm, to detect the companion. Using pyklip forward modeling, we constrain the relative astrometry to 1–2 mas precision and achieve sufficient photometric precision (±0.2 mag, 3% error) to detect changes in the Hα contrast of the companion over time. In order to accurately determine the relative astrometry of the companion, we conduct an astrometric calibration of the MagAO/VisAO camera against 20 yr of Keck/NIRC2 images of the Trapezium cluster. We demonstrate agreement of our VisAO astrometry with other published positions for HD 142527 B, and use orbitize! to generate a posterior distribution of orbits fit to the relative astrometry of HD 142527 B. Our data suggest that the companion is close to periastron passage, on an orbit significantly misaligned with respect to both the wide circumbinary disk and the recently observed inner disk encircling HD 142527 A. We translate observed Hα contrasts for HD 142527 B into mass accretion rate estimates on the order of 4–9 × 10−10 M ⊙ yr−1. Photometric variation in the Hα excess of the companion suggests that the accretion rate onto the companion is variable. This work represents a significant step toward observing accretion-driven variability onto protoplanets, such as PDS 70 b&c.

Pre-main sequence stars in LH 91

Aims. We study the accretion properties of pre-main sequence (PMS) low-mass stars in the LH 91 association within the Large Magellanic Clouds. Methods. Using optical multiband photometry obtained with the Hubble Space Telescope, we identify 75 candidates showing Hα excess emission above the 3σ level with equivalent width EWHα ⩾ 10 Å. We estimate the physical parameters (effective temperature, luminosity, age, mass, accretion luminosity, and mass accretion rate) of the PMS stellar candidates. Results. The age distribution suggests a period of active star formation ranging from a few million years up to ∼60 Myr with a gap between ∼5 Myr and 10 Myr. The masses of the PMS candidates span from 0.2 M⊙ for the cooler objects to 1.0 M⊙ with a median of ∼0.80 M⊙. The median value of the accretion luminosity of our 75 PMS stars is about 0.12 L⊙, the median value of the mass accretion rate is about 4.8 × 10−9 M⊙ yr−1 with higher values for the younger population (∼1.2 × 10−8 M⊙ yr−1), and lower values for the older candidates (∼4.7 × 10−9 M⊙ yr−1). We compare our results with findings for LH 95, the closest region to LH 91 for which accretion properties of PMS candidates were previously derived. An interesting qualitative outcome is that LH 91 seems to be in a more evolved stage. Moreover, we find that the PMS candidates are distributed homogeneously, without any evidence of clumps around more massive stars.

HST/WFC3 Hα Direct-imaging Detection of a Pointlike Source in the Disk Cavity of AB Aur

Accreting protoplanets enable the direct characterization of planet formation. As part of a high-contrast imaging search for accreting planets with the Hubble Space Telescope (HST) Wide Field Camera 3, we present Hα images of AB Aurigae (AB Aur), a Herbig Ae/Be star harboring a transition disk. The data were collected in two epochs of direct-imaging observations using the F656N narrowband filter. After subtracting the point-spread function of the primary star, we identify a pointlike source located at a position angle of 182.°5 ± 1.°4 and a separation of 600 ± 22 mas relative to the host star. The position is consistent with the recently identified protoplanet candidate AB Aur b. The source is visible in two individual epochs separated by ∼50 days, and the Hα intensities in the two epochs agree. The Hα flux density is F ν = 1.5 ± 0.4 mJy, 3.2 ± 0.9 times the optical continuum determined by published HST/STIS photometry. In comparison to PDS 70 b and c, the Hα excess emission is weak. The central star is accreting and the stellar Hα emission has a similar line-to-continuum ratio as seen in AB Aur b. We conclude that both planetary accretion and scattered stellar light are possible sources of the Hα emission, and the Hα detection alone does not validate AB Aur b as an accreting protoplanet. Disentangling the origin of the emission will be crucial for probing planet formation in the AB Aur disk.

GASP XXXIV: Unfolding the Thermal Side of Ram Pressure Stripping in the Jellyfish Galaxy JO201

Abstract X-ray studies of jellyfish galaxies play a crucial role in understanding the interactions between the interstellar medium (ISM) and the intracluster medium (ICM). In this paper, we focused on the jellyfish galaxy JO201. By combining archival Chandra observations, Multi Unit Spectroscopic Explorer Hα cubes, and maps of the emission fraction of the diffuse ionized gas, we investigated both its high-energy spectral properties and the spatial correlation between its X-ray and optical emissions. The X-ray emission of JO201 is provided by both the Compton-thick active galactic nucleus (L = 2.7 · 1041 erg s−1, not corrected for intrinsic absorption) and an extended component (L 1.9–4.5 · 1041 erg s−1) produced by a warm plasma (kT keV), whose luminosity is higher than expected from the observed star formation (L 3.8 · 1040erg s−1). The spectral analysis showed that the X-ray emission is consistent with the thermal cooling of hot plasma. These properties are similar to the ones found in other jellyfish galaxies showing extended X-ray emission. A point-to-point analysis revealed that this X-ray emission closely follows the ISM distribution, whereas CLOUDY simulations proved that the ionization triggered by this warm plasma would be able to reproduce the [O i]/Hα excess observed in JO201. We conclude that the galactic X-ray emitting plasma originates on the surface of the ISM as a result of the ICM–ISM interplay. This process would entail the cooling and accretion of the ICM onto the galaxy, which could additionally fuel the star formation, and the emergence of [O i]/Hα excess in the optical spectrum.

Searching for Active Low-mass Stars in the CMa Star-forming Region: Multi-band Photometry with T80S

Abstract An exotic environment surrounds the young stellar groups associated with the Canis Major (CMa) OB1/R1 region, which probably was formed under feedback from at least three supernova events having occurred a few million years ago. We use astrometric data from the Gaia-DR2 to confirm the membership of the stars in CMa R1, based on proper motion and parallax, which revealed 514 new members and candidates. The mean age of 5 Myr estimated from the color–magnitude diagram characterizes the sources as likely pre-main-sequence candidates. In total, a sample of 694 stars detected with the T80-South telescope was analyzed according to different color–color diagrams, which were compared with theoretical colors from evolutionary models, aiming to reveal the objects that exhibit color excess due to accretion processes. Accretion and magnetic activity were also explored on the basis of empirical flux–flux relation, such as F 660 and F 861 that are related to Hα and Ca ii triplet emission, respectively. A low fraction (∼3 percent) of the sample have Hα excess and other colors expected for stars exhibiting chromospheric activity. The number of Class I and Class II objects, identified by the infrared (Wide-field Infrared Survey Explorer) colors, indicates a disk fraction of ∼6 percent, which is lower than that expected for stellar clusters with a similar age. Such a large sample of objects associated with CMa R1 without evidences of circumstellar accretion can be interpreted as a lack of disk-bearing stars, unusual for young star-forming regions. However, this may be explained as the result of supernova events.

Photometric Determination of the Mass Accretion Rates of Pre-main-sequence Stars. VI. The Case of LH 95 in the Large Magellanic Cloud*

Abstract We report on the accretion properties of low-mass stars in the LH 95 association within the Large Magellanic Cloud. Using noncontemporaneous wideband optical and narrowband Hα photometry obtained with the Hubble Space Telescope, we identify 245 low-mass pre-main-sequence (PMS) candidates showing Hα excess emission above the 4σ level. We derive their physical parameters, including effective temperatures, luminosities, masses (M ⋆), ages, accretion luminosities, and mass accretion rates ( ). We identify two different stellar populations: younger than ∼8 Myr with median yr−1 (and M ⋆ ∼ 0.15–1.8 M ⊙) and older than ∼8 Myr with median yr−1 (and M ⋆ ∼ 0.6–1.2 M ⊙). We find that the younger PMS candidates are assembled in groups around Be stars, while older PMS candidates are uniformly distributed within the region without evidence of clustering. We find that in LH 95 decreases with time more slowly than what is observed in Galactic star-forming regions (SFRs). This agrees with the recent interpretation, according to which higher metallicity limits the accretion process in both rate and duration due to higher radiation pressure. The –M ⋆ relationship shows different behavior at different ages, becoming progressively steeper at older ages, indicating that the effects of mass and age on cannot be treated independently. With the aim to identify reliable correlations between mass, age, and , we used a multivariate linear regression fit between these parameters for our PMS candidates. The comparison between our results and those obtained in other SFRs of our Galaxy and the Magellanic Clouds confirms the importance of the metallicity for the study of the evolution in clusters with different environmental conditions.

MIRIS Paα Galactic Plane Survey. I. Comparison with IPHAS Hα in ℓ = 96°–116°

Abstract The Multipurpose InfraRed Imaging System (MIRIS) performed the MIRIS Paα Galactic Plane Survey (MIPAPS), which covers the entire Galactic plane within the latitude range of at Paα (1.87 μm). We present the first result of the MIPAPS data extracted from the longitude range of –116.°3 and demonstrate the quality and scientific potential of the data by comparing them with Hα maps obtained from the INT Photometric Hα Survey (IPHAS) data. We newly identify 90 H ii region candidates in the WISE H ii region catalog as definite H ii regions by detecting the Paα and/or Hα recombination lines, out of which 53 H ii regions are detected at Paα. We also report the detection of an additional 29 extended and 18 point-like sources at Paα. We estimate the E(B−V) color excesses and total Lyman continuum luminosities for H ii regions by combining the MIPAPS Paα and IPHAS Hα fluxes. The E(B−V) values are found to be systematically lower than those estimated from point stars associated with H ii regions. Utilizing the MIPAPS Paα and IPHAS Hα images, we obtain an E(B−V) map for the entire region of the H ii region Sh2-131 with an angular size of ∼2.°5. The E(B−V) map shows not only numerous high-extinction filamentary features but also negative E(B−V) regions, indicating Hα excess. The Hα excess and systematic underestimation of E(B−V) are attributed to light scattered by dust.

Star Formation in Galaxies at z ∼ 4–5 from the SMUVS Survey: A Clear Starburst/Main-sequence Bimodality for Hα Emitters on the SFR–M* Plane

Abstract We study a large galaxy sample from the Spitzer Matching Survey of the UltraVISTA ultra-deep Stripes (SMUVS) to search for sources with enhanced 3.6 μ m fluxes indicative of strong Hα emission at z = 3.9 – 4.9 . We find that the percentage of “Hα excess” sources reaches 37%–40% for galaxies with stellar masses log 10 ( M * / M ⊙ ) ≈ 9 – 10 and decreases to < 20 % at log 10 ( M * / M ⊙ ) ∼ 10.7 . At higher stellar masses, however, the trend reverses, although this is likely due to active galactic nucleus contamination. We derive star formation rates (SFR) and specific SFR (sSFR) from the inferred Hα equivalent widths of our “Hα excess” galaxies. We show, for the first time, that the “Hα excess” galaxies clearly have a bimodal distribution on the SFR–M* plane: they lie on the main sequence of star formation (with log 10 ( sSFR / yr − 1 ) < − 8.05 ) or in a starburst cloud (with log 10 ( sSFR / yr − 1 ) > − 7.60 ). The latter contains ∼ 15 % of all the objects in our sample and accounts for > 50 % of the cosmic SFR density at z = 3.9 – 4.9 , for which we derive a robust lower limit of 0.066 M ⊙ yr − 1 Mpc − 3 . Finally, we identify an unusual > 50 σ overdensity of z = 3.9 – 4.9 galaxies within a 0.20 × 0.20 arcmin2 region. We conclude that the SMUVS unique combination of area and depth at mid-IR wavelengths provides an unprecedented level of statistics and dynamic range that are fundamental to revealing new aspects of galaxy evolution in the young universe.

A HIGH-RESOLUTION MULTIBAND SURVEY OF WESTERLUND 2 WITH THE HUBBLE SPACE TELESCOPE. II. MASS ACCRETION IN THE PRE-MAIN-SEQUENCE POPULATION

ABSTRACT We present a detailed analysis of the pre-main-sequence (PMS) population of the young star cluster Westerlund 2 (Wd2), the central ionizing cluster of the H ii region RCW 49, using data from a high-resolution multiband survey with the Hubble Space Telescope. The data were acquired with the Advanced Camera for Surveys in the F555W, F814W, and F658N filters and with the Wide Field Camera 3 in the F125W, F160W, and F128N filters. We find a mean age of the region of 1.04 ± 0.72 Myr. The combination of dereddened F555W and F814W photometry in combination with F658N photometry allows us to study and identify stars with Hα excess emission. With a careful selection of 240 bona-fide PMS Hα excess emitters we were able to determine their Hα luminosity, which has a mean value . Using the PARSEC 1.2S isochrones to obtain the stellar parameters of the PMS stars, we determined a mean mass accretion rate per star. A careful analysis of the spatial dependence of the mass accretion rate suggests that this rate is ∼25% lower in the center of the two density peaks of Wd2 in close proximity to the luminous OB stars, compared to the Wd2 average. This rate is higher with increasing distance from the OB stars, indicating that the PMS accretion disks are being rapidly destroyed by the far-ultraviolet radiation emitted by the OB population.

Hα photometry of low-mass stars in 47 Tucanae: chromospheric activity and exotica

We have used archival Hubble Space Telescope observations obtained with the Advanced Camera for Surveys to study the Hα emission properties of main-sequence stars in the globular cluster 47 Tucanae. Using a combination of multiband observations in the F606W, F814W and F658N bands, we search for stars showing Hα excess emission. An accurate photometric measurement of their Hα equivalent width allows us to identify objects with large Hα emission, which we attribute to mass accretion rather than enhanced chromospheric activity. The spatial position of some of these stars is coincident with that of known X-ray sources, and their location in the colour–magnitude diagram allows us to classify them as active binaries or cataclysmic variables (CVs). We show that this method, commonly adopted to study accreting discs in young stellar objects, can be successfully used to identify and characterize candidate CVs.

PROGRESSIVE STAR FORMATION IN THE YOUNG GALACTIC SUPER STAR CLUSTER NGC 3603

Early Release Science observations of the cluster NGC 3603 with the WFC3 on the refurbished Hubble Space Telescope allow us to study its recent star formation history. Our analysis focuses on stars with Hα excess emission, a robust indicator of their pre-main sequence (PMS) accreting status. The comparison with theoretical PMS isochrones shows that 2/3 of the objects with Hα excess emission have ages from 1 to 10 Myr, with a median value of 3 Myr, while a surprising 1/3 of them are older than 10 Myr. The study of the spatial distribution of these PMS stars allows us to confirm their cluster membership and to statistically separate them from field stars. This result establishes unambiguously for the first time that star formation in and around the cluster has been ongoing for at least 10–20 Myr, at an apparently increasing rate.

Hα imaging of X-ray sources in selected globular clusters with SOAR

AbstractI present results of a search for cataclysmic variables (CVs) and chromospherically active binaries (ABs) as counterparts to X-ray sources detected with Chandra in six Galactic globular clusters (GCs): M 4, M 28, M 30, M 71, M 80, and NGC 6752. Binary systems play a critical role in the evolution of GCs, serving as an internal energy source countering the tendency of GC cores to collapse. Theoretical studies predict dozens of CVs in the cores of some GCs (e.g., 130 for M 28, 40 for M 30). A number of such binaries are also expected outside the core radius. However, few CVs are known so far in GCs. Using the 4.1m SOAR telescope, I have found 25 stars with Hα excess in the observed clusters. Six are candidate CVs, five are candidate active binaries. The other 14 objects with Hα excess are probably foreground/background stars or extragalactic sources.

Hα Photometry of Two Contact Binaries

We carried out optical and Hα photometry of two contact binaries (V861 Herculis, EQ Tauri). The light curve modeling revealed stellar spots in both contact systems and strong Hα excess in the position of the observed stellar spots. A correlation was found between the V−R and R−Hα colour indices of V861 Her.

The “Príncipes de Asturias” nebula: a new quadrupolar planetary nebula from the IPHAS survey

Context. The Isaac Newton Telescope Photometric Ha Survey (IPHAS) is currently mapping the Northern Galactic plane reaching to r' = 20 mag with typically 1 resolution. Hundreds of Planetary Nebulae (PNe), both point-like and resolved, are expected to be discovered. We report on the discovery of the first new PN from this survey: it is an unusual object located at a large galactocentric distance and has a very low oxygen abundance. Aims. Detecting and studying new PNe will lead to improved estimates of the population size, binary fraction and lifetimes, and yield new insights into the chemistry of the interstellar medium at large galactocentric distances. Methods. Compact nebulae are searched for in the IPHAS photometric catalogue, selecting those candidates with a strong Hα excess in the r' -Hα vs. r' - i' colour-colour diagram. Searches for extended nebulae are by visual inspection of the mosaics of continuum-subtracted Ha images at a spatial sampling of 5 x 5 arcsec 2 . Follow-up spectroscopy enables confirmation of the PNe, and their physico-chemical study. Results. The first planetary nebula discovered via IPHAS imagery shows an intricate morphology: there is an inner ring surrounding the central star, bright inner lobes with an enhanced waist, and very faint lobular extensions reaching up to more than 100. We classify it as a quadrupolar PN, a rather unusual class of planetary showing two pairs of misaligned lobes. From long-slit spectroscopy we derive T e [NII] = 12 800 ± 1000 K, N e = 390 ± 40 cm -3 , and chemical abundances typical of Peimbert's type I nebulae (He/H = 0.13, N/O = 1.8) with an oxygen abundance of 12 + log(O/H) = 8.17 ± 0.15. A kinematic distance of 7.0 +4.5 -3.0 kpc is derived, implying an unusually large size of >4 pc for the nebula. The photometry of the central star indicates the presence of a relatively cool companion. This, and the evidence for a dense circumstellar disk and quadrupolar morphology, all of which are rare among PNe, support the hypothesis that this morphology is related to binary interaction.