Morten Andersen

Gemini Observatory · Gemini South

The Gemini North Adaptive Optics (GNAO) facility is the upcoming AO facility for Gemini North providing a state-of-the-art AO system for surveys and time domain science in the era of JWST and Rubin operations. GNAO will be optimized to feed the Gemini infrared Multi Object Spectrograph (GIRMOS). While GIRMOS is the primary science driver for defini...

In order to obtain a complete census of the stellar and substellar population, down to a few M_(Jup) in the ~1 Myr old Orion Nebula Cluster, we used the infrared channel of the Wide Field Camera 3 of the Hubble Space Telescope with the F139M and F130N filters. These bandpasses correspond to the 1.4 μm H₂O absorption feature and an adjacent line-fre...

We study the gas kinematics and dynamics of the massive protocluster G286.21+0.17 with the Atacama Large Millimeter/submillimeter Array using spectral lines of $C^{18}O$(2-1), $N_2D^+$(3-2), $DCO^+$(3-2) and $DCN$(3-2). On the parsec clump scale, $C^{18}O$ emission appears highly filamentary around the systemic velocity. $N_2D^+$ and $DCO^+$ are mo...

We present a near-infrared (NIR) variability analysis for an 6\arcmin $\times$ 6\arcmin region, which encompasses the massive protocluster G286.21+0.17. The total sample comprises more than 5000 objects, of which 562 show signs of a circumstellar disk based on their infrared colors. The data includes HST observations taken in two epochs separated b...

We study the gas kinematics and dynamics of the massive protocluster G286.21+0.17 with the Atacama Large Millimeter/submillimeter Array using spectral lines of C ¹⁸ O(2–1), (3–2), (3–2), and (3–2). On the parsec clump scale, C ¹⁸ O emission appears highly filamentary around the systemic velocity, and are more closely associated with the dust contin...

In order to obtain a complete census of the stellar and sub-stellar population, down to a few M$_{Jup}$ in the $\sim1$ Myr old Orion Nebula Cluster, we used the infrared channel of the Wide Field Camera 3 of the Hubble Space Telescope with the F139M and F130N filters. These bandpasses correspond to the $1.4 \mu$m H$_2$O absorption feature and an ad...

Gemini Observatory is developing a queue-operated multi-conjugate adaptive optics facility, GNAO, for the 8-m Gemini North telescope. GNAO is part of the "Gemini in the Era of Multi-Messenger Astronomy" (GEMMA) program which is funded by the National Science Foundation and aims at advancing Gemini's leadership role in high angular resolution and ra...

Aims. We aim to evaluate the near-infrared colors of brown dwarfs as observed with four major infrared imaging space observatories: the Hubble Space Telescope (HST), the James Webb Space Telescope (JWST), the Euclid mission, and the WFIRST telescope. Methods. We used the SPLAT SPEX/ISPEX spectroscopic library to map out the colors of the M-, L-, an...

AIMS: We aim to evaluate the near-infrared colors of brown dwarfs as observed with four major infrared imaging space observatories: the Hubble Space Telescope (HST), the James Webb Space Telescope (JWST), the Euclid mission, and the WFIRST telescope. METHODS: We used the SPLAT SPEX/ISPEX spectroscopic library to map out the colors of the M-, L-, an...

We study the core mass function (CMF) of the massive protocluster G286.21+0.17 with the Atacama Large Millimeter/submillimeter Array via 1.3 mm continuum emission at a resolution of 1.0" (2500 au). We have mapped a field of 5.3'$\times$5.3' centered on the protocluster clump. We measure the CMF in the central region, exploring various core detectio...

We study the core mass function (CMF) of the massive protocluster G286.21+0.17 with the Atacama Large Millimeter/submillimeter Array via 1.3~mm continuum emission at a resolution of 1.0\arcsec\ (2500~au). We have mapped a field of 5.3\arcmin$\times$5.3\arcmin\ centered on the protocluster clump. We measure the CMF in the central region, exploring v...

We report a discovery of shocked gas from the supernova remnant (SNR) G357.7+0.3. Our millimeter and submillimeter observations reveal broad molecular lines of CO(2-1), CO(3-2), CO(4-3), 13CO (2-1) and 13CO (3-2), HCO^+ and HCN using HHSMT, Arizona 12-Meter Telescope, APEX and MOPRA Telescope. The widths of the broad lines are 15-30 kms, and the de...

We report a discovery of shocked gas from the supernova remnant (SNR) G357.7+0.3. Our millimeter and submillimeter observations reveal broad molecular lines of CO(2-1), CO(3-2), CO(4-3), 13CO (2-1) and 13CO (3-2), HCO^+ and HCN using HHSMT, Arizona 12-Meter Telescope, APEX and MOPRA Telescope. The widths of the broad lines are 15-30 kms, and the de...

The advent of Wide Field Adaptive Optics (WFAO) systems marks the beginning of a new era in high spatial resolution imaging. The newly commissioned Gemini South Multi-Conjugate Adaptive Optics System (GeMS) combined with the infrared camera Gemini South Adaptive Optics Imager (GSAOI), delivers quasi diffraction-limited images over a field of 2 arc-...

In the catalog of M-dwarfs presented in Holwerda et al. (2014, H14 hereafter), there is an issue with the conversion from celestial coordinates to Galactic ones, done with pyephem a wrapper around a trusted and vetted library ephermis. Here we present the corrected coordinates (using AstroPy) and distances based on AB magnitudes. We have amended th...

Context. Recently discovered scattered light from molecular cloud cores in the wavelength range 3–5 μm (called “coreshine”) seems to indicate the presence of grains with sizes above 0.5 μm. Aims. We aim to analyze 3.6 and 4.5 μm coreshine from molecular cloud cores to probe the largest grains in the size distribution. Methods. We analyzed dedicated...

Recently discovered scattered light from molecular cloud cores in the wavelength range 3-5 {\mu}m (called "coreshine") seems to indicate the presence of grains with sizes above 0.5 {\mu}m. We aim to analyze 3.6 and 4.5 {\mu}m coreshine from molecular cloud cores to probe the largest grains in the size distribution. We analyzed dedicated deep Cycle...

Context. Recently discovered scattered light from molecular cloud cores in the wavelength range 3-5 μm (called "coreshine") seems to indicate the presence of grains with sizes above 0.5 μm. Aims. We aim to analyze 3.6 and 4.5 μm coreshine from molecular cloud cores to probe the largest grains in the size distribution. Methods. We analyzed dedicated...

Supernovae (SNe) produce, fragment and destroy dust, molecules and nucleosynthetic elements, and reshape and modify the ISM. I will review recent infrared observations of supernova remnants (SNRs) and SNe which show that SNe are important sites of dust and molecule formation and are major dust creators in the Universe. Detection of carbon monoxide...

Context: Observations of scattered light in the 1-5 $\mu$m range have revealed dust grains in molecular cores with sizes larger than commonly inferred for the diffuse interstellar medium. It is currently unclear whether these grains are grown within the molecular cores or are an ubiquitous component of the interstellar medium. Aims: We investigate...

Context. Using observations to deduce dust properties, grain size distribution, and physical conditions in molecular clouds is a highly degenerate problem. Aims. The coreshine phenomenon, a scattering process at 3.6 and 4.5 μm that dominates absorption, has revealed its ability to explore the densest parts of clouds. We want to use this effect to c...

We use $N$-body simulations to compare the evolution of spatial distributions of stars and brown dwarfs in young star-forming regions. We use three different diagnostics; the ratio of stars to brown dwarfs as a function of distance from the region's centre, $\mathcal{R}_{\rm SSR}$, the local surface density of stars compared to brown dwarfs, $\Sigm...

The recently discovered coreshine effect can aid in exploring the core properties and in probing the large grain population of the ISM. We discuss the implications of the coreshine detected from the molecular cloud core L1506C in the Taurus filament for the history of the core and the existence of a primitive ISM component of large grains becoming...

We present a tally of Milky Way late-type dwarf stars in 68 Wide Field Camera 3 (WFC3) pure-parallel fields (227 arcmin2) from the Brightest of Reionizing Galaxies survey for high-redshift galaxies. Using spectroscopically identified M-dwarfs in two public surveys, the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey and the Early Release S...

Recently discovered scattered light at 3-5 $\mu$m from low-mass cores (so-called "coreshine") reveals the presence of grains around 1 $\mu$m, which is larger than the grains found in the low-density interstellar medium. But only about half of the 100+ cores investigated so far show the effect. This prompts further studies on the origin of this dete...

Recently discovered scattered light at 3-5 µm from low-mass cores (so-called "coreshine") reveals the presence of grains around 1 µm. But only a fraction of the cores investigated so far show the effect. We derive a simple limit for detecting scattered light from a low-mass core can be derived. The extinction by the core prohibits detection in brig...

Context. The largest grains (0.5−1 μm) in the interstellar size distribution are efficient in scattering near- and mid-infrared radiation. These wavelengths are therefore particularly well suited to probe the still uncertain high-end of the size distribution. Aims. We investigate the change in appearance of a typical low-mass molecular core from...

The full fields covered by the HST ACS/WFC and WFPC2 surveys are shown, respectively, in Figures 2 and 3. Both are approximately centered at RA=05:35:00 and DEC=-5:26:00 (J2000), approximately 200" to the SW of the Trapezium asterism and extend over about one-sixth of a square degree. In particular, the full ACS mosaic covers 627arcmin2, whereas th...

Galactic starburst clusters represent the most extreme mode of present-day star formation in the Milky Way, and are ideal laboratories for studies over the entire stellar mass range from less then 0.1 to more than 120 solar masses. We report on the results of our adaptive optics and HST high angular resolution studies comprising both multi-epoch as...

The Hubble Space Telescope (HST) Treasury Program on the Orion Nebula Cluster has used 104 orbits of HST time to image the Great Orion Nebula region with the Advanced Camera for Surveys (ACS), the Wide-Field/Planetary Camera 2 (WFPC2) and the Near Infrared Camera and Multi Object Spectrograph (NICMOS) instruments in 11 filters ranging from the U-ba...

We request dedicated 4.5 micron observations of a selected sample of molecular cores which are known to be characterized by 'coreshine'. These observations will allow us to investigate the detailed distribution of grain sizes and its dependence on optical depth (or density profile) inside the cores. Investigating grain coagulation in dense molecula...

We highlight the main results of a multi-wavelenght study of the super star clusters NGC 3603 and 30 Doradus, recently observed with Wide Field Camera 3 (WFC3) on board the HST.

We present a new method to determine the age spread of resolved stellar populations in a starburst cluster. The method relies on a two-step process. In the first step, kinematic members of the cluster are identified based on multi-epoch astrometric monitoring. In the second step, a Bayesian analysis is carried out, comparing the observed photometri...

Context. Westerlund I is the richest young cluster currently known in our Galaxy, making it one of the most massive clusters for which we can resolve the individual stars even in the crowded centre. This makes it an ideal target to assess whether massive clusters formed currently will remain bound or will disperse and contribute significantly to th...

We present Spitzer Multiband Imaging Photometer (MIPS) spectral energy distribution (SED) and Infrared Spectrograph (IRS) observations of 14 Galactic supernova remnants (SNRs) previously identified in the GLIMPSE survey. We find evidence for SNR/molecular cloud interaction through detection of [O I] emission, ionic lines, and emission from molecula...

We present Spitzer MIPS SED and IRS observations of 14 Galactic Supernova Remnants previously identified in the GLIMPSE survey. We find evidence for SNR/molecular cloud interaction through detection of [O I] emission, ionic lines, and emission from molecular hydrogen. Through black-body fitting of the MIPS SEDs we find the large grains to be warm,...

Photometry for sources in the HST/NICMOS survey and their location. (1 data file).

We present deep HST/NICMOS Camera 3 F110W and F160W imaging of a 26'x33', corresponding to 3.1pcx3.8pc, non-contiguous field towards the Orion Nebula Cluster (ONC). The main aim is to determine the ratio of low--mass stars to brown dwarfs for the cluster as a function of radius out to a radial distance of 1.5pc. The sensitivity of the data outside...

Using observations obtained with the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope (HST), we have studied the properties of the stellar populations in the central regions of 30 Dor, in the Large Magellanic Cloud. The observations clearly reveal the presence of considerable differential extinction across the field. We characterise a...

Supernovae have a formidable impact on the dynamics, chemistry and evolution of their local environments. Shocks carve into dense molecular clouds, radiatively cooling the remnant through strong molecular hydrogen and atomic lines. One of important postshock reaction is to convert atomic oxygen to molecular form such as CO, OH and water and these l...

We used near-infrared data obtained with the Wide Field Camera 3 on the Hubble Space Telescope to identify objects having the colors of brown dwarfs (BDs) in the field of the massive galactic cluster NGC 3603. These are identified through a combination of narrow- and medium-band filters which span the J and H bands and are particularly sensitive to...

We use near-infrared data obtained with the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope to identify objects having the colors of brown dwarfs (BDs) in the field of the massive galactic cluster NGC 3603. These are identified through use of a combination of narrow and medium band filters spanning the J and H bands, and which are particul...

I present observations of shock-processed PAHs and dust in supernova remnants (SNRs). Supernova shocks are one of the primary sites destroying, fragmenting and altering interstellar PAHs and dust. Studies of PAHs through supernova shocks had been limited because of confusion with PAHs in background emission. Spitzer observations with high sensitivi...

Using high resolution optical spectroscopy (R = 53.000) we constrain the dynamical state of Westerlund 1, perhaps the most massive Population I cluster in the Milky Way. Our goal is to understand whether massive clusters such as Westerlund 1 emerge bound or whether they will disperse and contribute significantly to the field star population. The cl...

Early release science observations of the cluster NGC3603 with the WFC3 on the refurbished HST allow us to study its recent star formation history. Our analysis focuses on stars with Halpha 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 obje...

We present deep Hubble Space Telescope (HST) NICMOS 2 F160W band observations of the central 56*57" (14pc*14.25pc) region around R136 in the starburst cluster 30 Dor (NGC 2070) located in the Large Magellanic Cloud. Our aim is to derive the stellar Initial Mass Function (IMF) down to ~1 Msun in order to test whether the IMF in a massive metal-poor...

SDSS J1600+0748 is the only hot sdO star for which unambiguous multiperiodic luminosity variations have been reported so far. These rapid variations, with periods in the range from 60 s to 120 s, are best qualitatively explained in terms of pulsational instabilities, but the exact nature of the driving mechanism has remained a puzzle. Models of sdO...

We present dust features and masses observed in young supernova remnants (SNRs) with Spitzer IRS mapping and staring observations of four youngest supernova remnants: SNR 1E102.2-7219 (E0102) in the SMC, Cas A and G11.2-0.3 in our Galaxy, and N132D in the LMC. The spectral mapping data revealed a number of dust features which include 21 micron-peak...

We report the likely detection of near-infrared 2.29 μm first overtone carbon monoxide (CO) emission from the young supernova (SN) remnant Cassiopeia A (Cas A). The continuum-subtracted CO filter map reveals CO knots within the ejecta-rich reverse shock. We compare the first overtone CO emission with that found in the well studied supernova SN 1987...

With Spitzer IRS, we have obtained sensitive low-resolution spectroscopy from 5 to 35 μm for six supernova remnants (SNRs) that show evidence of shocked molecular gas: Kes 69, 3C 396, Kes 17, G346.6–0.2, G348.5–0.0, and G349.7+0.2. Bright pure rotational lines of molecular hydrogen are detected at the shock front in all remnants, indicative of radi...

Context. SDSS J160043.6+074802.9 (J1600+0748 for short) is the only hot sdO star for which unambiguous multiperiodic luminosity variations have been reported so far. These rapid variations, with periods in the range from ~60 s to ~120 s, are best qualitatively explained in terms of pulsational instabilities, but the exact nature of the driving mech...

We present a combined analysis of the low-mass initial mass function (IMF) for seven star-forming regions. We first demonstrate that the ratios of stars to brown dwarfs are consistent with a single underlying IMF. By assuming that the underlying IMF is the same for all seven clusters and by combining the ratio of stars to brown dwarfs from each clu...

Despite over 50 years of active research, a key question in galactic astronomy remains unanswered: is the initial mass function {IMF} of stars and sub-stellar objects universal, or does it depend on initial conditions? The answer has profound consequences for the evolution of galaxies as well as a predictive theory of star formation. Work to date s...

We report on Chandra ACIS-I observations of the Eagle Nebula containing the young Galactic cluster NGC~6611 and the dark columns called the ``Pillars of Creation''. We find that NGC~6611 contains a rich collection of young X-ray emitting stars, but the EGGs at the edge of the pillars are not detected at levels below the Orion young stellar objects.

We have analyzed Hubble Space Telescope NICMOS2 F110W-, F160W-, F165M-, and F207M-band images covering the central 1' × 1' region of the cluster associated with Mon R2 in order to constrain the initial mass function (IMF) down to 20MJ. The flux ratio between the F165M and F160W bands was used to measure the strength of the water-band absorption fea...

Shocks from supernova are responsible for destruction of interstellar dust and possibly for the creation of poly aromatic hydrocarbons (PAHs, Jones et al 1996). However, the rate and effectiveness of the creation of PAHs in supernova shocks are largely unknown quantities. Only with the sensitivity and spatial resolution with SPITZER has it been pos...

Infrared emission from interacting supernova remnants is rich in atomic fine-structure and molecular rovibrational lines which allows a detailed characterization of the shock conditions present. With Spitzer IRS and MIPS-SED we have obtained sensitive, high spatial resolution spectroscopy between 5.2 and 95 microns for 14 interacting remnants in th...

We present and analyze the first high-resolution X-ray images ever obtained of the Eagle Nebula star-forming region. On 2001 July 30 the Chandra X-ray Observatory obtained a 78 ks image of the Eagle Nebula (M 16) that includes the core of the young galactic cluster NGC 6611 and the dark columns of dust and cold molecular gas in M 16 known as the Pi...

We present results from deep near-infrared H band observations of the central square arcminute of the 30 Dor cluster in the LMC, aimed at detecting premain-sequence stars down to 1 M \odot_\odot . We do not see any change in the slope of the luminosity function down to the completeness limit anywhere within the observed field. We suggest the flatt...

Any successful theory of star formation must be able to explain the IMF and how it varies (if it does vary) as a function of the star formation environment. Because the stellar part of the IMF appears to be similar for clusters within 2 kpc (e.g. Meyer et al. 2000) we are compelled to expand the search to regions with more extreme conditions than n...

Any predictive theory of star formation must explain observed variations (or lack thereof) in the initial mass function. Recent work suggests that we might expect quantitative variations in the IMF as a function of metallicity (Larson 2005) or magnetic field strength (Shu et al. 2004). We summarize results from several on-going studies attempting t...

The starburst IMF is probably as much of theoretical interest and practical relevance as it is a subject of observational controversy. In this conference paper we review the most common methods (star counts, dynamical masses, and line ratios) to derive or constrain the IMF, and discuss potential problems and shortcomings that often lead to claims o...

We present millimetre, optical, and near-infrared observations of M 16 in the vicinity of the Herbig-Haro object HH 216. The line profiles of the CO (J=2-1) spectra are broad and consist of both emission originating from four warm molecular cores and a large cloud or cloud system across the whole field. The CS (J=2-1) and the C18O (J=2-1) lines are...

NGC 3603, an open cluster embedded in the largest Galactic H II region, contains some of the most luminous, massive stars known in the Galaxy. It may serve as a good analog of star-forming regions in external starburst galaxies. The recent deep (50 Ksec) {Chandra} imaging of NGC 3603 revealed that its X-Ray emission is dominated by the bright Wolf-...

In this article, we hope to illustrate the great qualitative and quantitative strides that star-formation studies have taken in the past few years, by looking at three highlights from our own work using the ESO Very Large Telescope UT1, Antu, and its facility near-infrared camera/spectrograph, ISAAC. In particular, we have chosen examples which ill...

We present a high-angular-resolution molecular line and millimeter continuum study of the massive star formation site IRAS 05358+3543. The most remarkable feature is a highly collimated (collimation factor ~10) and massive (>10 M_sun) bipolar outflow of 1 pc length, which is part of a quadrupolar outflow system. The three observed molecular outflow...

We present a deep, high spatial resolution (0.35 arcsec FWHM), near-infrared (1-2.5 micron) imaging survey of the Eagle Nebula, M16, made with the VLT, centred on the famous elephant trunks. We compare these data with the existing HST optical images to search for evidence of ongoing or recent star formation in the trunks, and in particular in the 7...

We present the first infrared luminosity function in the 30 Doradus star cluster obtained with the HST NIC1 camera (0.043'' pixel-1) in the F160W (H-band) filter. Despite diffraction limited resolution (0.15''), crowding and blending is so severe that the cluster centre R136 cannot be studied. Instead a neighbouring NIC1 field (about 15'' away from...

We report the discovery of a wide pair (93 arcsec angular separation) of extremely cool ($T_{eff}<4000$ K) white dwarfs with a very large common proper motion ($\sim1.9$ arcsec/yr). The objects were discovered in a high proper motion survey in the poorly investigated southern sky region with $\delta<-60^{\circ}$ using SuperCOSMOS Sky Survey (SSS) d...

We present intermediate resolution spectroscopy and near infrared photometry of NOVA Sco 2001 (V1178 Sco), which was first detected May 13th 2001 and reported June 21th 2001, and obtained by us the same day. We also retrieved very accurate astrometry of the target in this very crowded field. This is needed to be able to do follow up observations of...

This white paper was conceived at a workshop on Far-Infrared /Submillimeter Astronomy from Space held in Pasadena, CA, May 28 - 30, 2008. A Special Session held at the January 2009 AAS meetings provided additional recommendations from the wider astronomical community. The individuals listed below were contributors to the 2008 workshop or are FIR/SM...

We present the preliminary results of a panchromatic study of the cluster NGC 3603 based on observations obtained with the Wide Field Camera 3 (WFC3) on board the HST. The data cover an area of about 2' x 2' in various broad- and narrow-band filters at visible and near infrared wavelengths (V, R, Halpha, I, J, H). We use these data to derive accura...

The origin of brown dwarfs (BDs) is an important component of the theory of star formation that still remains somewhat mysterious. The new Wide Field Camera 3 (WFC3) on board the HST is optimized at both UV and IR wavelengths and offers an unique opportunity for a major advancement in this field. In this contribution we show the possibilities offer...

Using observations obtained with the WFC3 camera on board the Hubble Space Telescope, we have studied the star formation properties of the central regions of 30 Dor, in the Large Magellanic Cloud. The observations clearly reveal the presence of considerable differential extinction across the field. We characterise and quantify this effect using you...